*
…I kept getting lost in the thread…so here it is reiterated:
the object is to arrive at a CONSENSUS for the overall strategy in handling the envelope of a structure:…..
here’s the consensus as I currently see it:
1) moisture always moves from wet to dry
2) warm air carries more moisture than cool air
3) vapor barriers (VB) are a helpful part of the strategy
4) Air Movement Retarders are a helpful part of the strategy.
5) Reducing the temperature in the attic will lower the cooling load, BUT there may be a more effective strategy.
6) Insulation is a GOOD thing and (7) more insulation is a better thing.
8) Homeowners don’t want to live in caves, they like windows and doors.
9) In some locations , vapor barriers are MUCH more important than Air Retarders, eg:
Slab on Grade: with some POSSIBLE exceptions (in a structure that is not conditioned or insulated)
Crawl Space FLOORS
Basement walls
Basement flor slabs
10) when you take care of one of these problems, the other problems become MORE significant….but hopefully the sum of the problems becomes less.
a corollary: don’t make things worse.
11) REGIONAL climate hac a VERY significant effect on the total strategy for solving these building envelope problems
….MICRO climates have tremendous significance eg: one community near a body of water will have a much different set of problems and effective strategies than another community even 10 miles away.
….MICRO climates even pertain to the specific site conditions and the orientation of the structure, and even which side of the structure we are talking about….the south side is very different from the north, and the side with the prevailing winds is different than the downwind side…
12) given the right budget (our customers ALWAYS have a budget)..
the strategy for the house should include:
heating, cooling, humidity, air cleaning, combustion products…..
insulation, vapor barriers, venting, infiltration,……
crack loss (infiltration again, NOT the
great American tradgedy), testing and verification…
workmanship, maintenance (ease of, durability, budget for, etc.)
and all of these strategies should be designed with KISS as a primary virtue. The average homeowner is not going to know or care about any of this until it is too late.
b don’t know much , but willing to learn…..Kermit
Replies
*
Hey Mike,
Thanks for inviting me to the party. I have been wading
through this and other threads of this nature at times, and
along with everyone else with an open mind, I am interested
in actual performance information, facts and possibly a look
at what the ideal situation in a)vented structures and
b)nonvented structures would be. I believe there is ample
room for both arguments to have merit in many different
cases.
It seems that in differing climates, there would be reasons
to sway towards one method over the other, but I'm just as
confused as ever about it all.
I don't mind the fights any more, sort of entertaining since
things got so slow and boring in the tavern. You've got
guts if you want to be the referee here. Too bad that it
screws up the information transfer, because there are people
here who know a lot more about it than me, and I'm not
nearly afraid to admit it.
So maybe we could start out with a discussion of basic
facts, like those you started to outline, and see if it can
stay civil long enough to get something concrete out of it.
MD
************** ************** **********
*Lstiburek writes in this month's JLC:"In a well insulated attic in a very cold climate (more than 8,000 heating degree days), there is not enough heat loss into an attic from the house to allow for much moisture removal through ventilation. That's because attic ventilation requires heat loss to remove moisture from attics. Cold air can't hold much moisture."So perhaps this is less a climate specific issue than a quality of insulation and air barrier issue. I believe Fred speaks from the point of view of building good air barriers and installing good insulation in an effective manner because, following his advice, I have achieved good results.
*Keepers of the flame, et all..., I do agree with the idea that envelope venting may be needed if the building envelope is of poor quality and moisture is being dumped into an uninsulated (unheated), cooler environment. As warm moist air hits the cool attic, the RH will jump, the dew point could be reached, and condensation could start in the attic. However, the venting is still the solution to a poor envelope problem. And the venting "solution", in some ways, creates additional problems needing additional "fixes".Controlling the moisture entering the unheated space seems to be the key. I think most agreee on that. For attic insulation, cells seem to be the better application due to its ability to "air seal" and to "absorb" and hold the moisture, then give it up as conditions warrant. In attics, its ability to absorb radiant is a definite plus.So, a partial quick list of issues that have been previously mentioned:*Control moisture entering the building envelope: **Basement/crawlspace **Air locks (mud rooms w 2 doors, etc) **Foaming window/door rough openings*Control moisture generated in envelope via exhaust vents: **Bathing **Cooking **Clothes Dryer **Eliminating humidifiers*Minimize negative pressure effects in house from exhaust vents: **Makeup air? **Prevent backdrafting of flues? **Elec dampers? **Heat exchangers?I'm still trying to figure a better way to insulate attic ceilings (rafter bays), where the attic is a living space. Personally, I'm not concerned with a shingle manufacturer's warranty. No one I work with is, either. However, I NEED to vent the roof. Not the house, but the rafter bays. It's an area my inspector won't budge on. "Local exceptions" to the code, etc. I'm in a "moderate" 4-season environment, southern New England. So...I need an airspace under the sheathing, and that creates my problem, at least as I see it. Ideally, I'd like to use DP cells in the rafter bays. They seem best at air sealing and at absorbing radiant pass-through. In order to DP, I need something to contain the cells on "top" to preserve the airspace. Using rigid foil-faced foam board insulation, tightly sealed/foamed against the rafters would give me a radiant barrier on top and, with proper support against the sheathing, would contain the cells. The top foil face could also provide a bit of protection against any moisture that entered, for whatever reason, either through the ridge vent or through shingle/sheathing failures. Not ideal protection, but it would keep the cells dry, so to speak. Yes the moisture would be sent to the soffit...Also...I'd want to furr out the rafters into the attic space (eventually to be a finished off living space) to prevent the rafters from acting as a heat sink from roof sheathing to drywall, and to allow a greater cells thickness. Also adding a layer or two of foam insulation on the inside, to be covered with gypsum board. more on that later.Proposed roof structure, inside to out:*5/8ths gypsum board*rigid foam board, maybe two layers, 2-3" thick total(?), joints offset/foamed*DP Cells...would be about 8-10 inches?*Ridgid foil-faced foam insulation*Air space*Roof sheathing*membrane/felt/shingles, etcMy understanding is that no poly should be used in conjunction with cells. Yes? No?My concern is that I'm creating a "cells sandwich"...with multiple condensing surfaces. Any moisture that does indeed get from the finished living area, through the gypsum and foam, gets into the cells. From there, theoretically, it could condense on the bottom of the foil faced insulation.Is this a valid concern? Will the cells be able to hold the moisture without rotting?If so, to me it would make sense to remove one of the foam layers...either the double layer of foam on the living side of the sandwich, or the foil-faced on the outside. Removing the inner layer could allow more moisture to enter the cells from the living area, through the drywall. If, however, I removed the foil-faced layer, I'd still need to replace it with something to contain the cells. IF I did the cells sandwich, I think I could attach the inside foam directly to the bottoms of the rafters. Depends on rafter depth, though, as I want a decent cells thickness. If, however, I omitted the inside foam layers, then I would furr the rafters so the gypum board would not be mounted directly to the rafters.My instinct is to maintain the inside foam to minimize infiltration into the cells. However, that still leaves me with a sandwich. Problem? Would it be better to simply replace the foil-faced insul with ply baffles under the sheathing...or, would the ply also act as a condensing surface? Or, could I use the foil-faced, but not seal it tightly agains the rafters...thus, while it adds insulating and radiant value, it does not prevent vapor from the cells, around the foam and the rafters, and into the air space. All solutions still sound objectionable to me.Essentially, I'm looking at a cathedral ceiling-type of structure in a finished attic space, with the requirement that there be an air space under the roof sheathing...Every solution, to me, has possible failures. I'm just not positive if I'm putting proper emphasis on either my solutions or my concerns. How's that for standing tall...in quicksand?Sorry if this is disjointed, my connection has dumped so I've written it in several two-minute sittings. I truly would appreciate any constructive input, ideas, concerns, etc. As I see it, it's the required airspace that's confusing me with multi condensing surfaces.Thanks, Mongo
*Mongo,Have you considered the simple alternative of using vented nailable insulation panels for the roof deck instead of multiple layers of various insulating materials? R-values range as high as 30 depending on the thickness of the foam and depth of the air space. These panels are constructed of rigid foam insulation with either OSB or plywood nailer panel sitting on sleepers. The result is a 1/2" to 3/4" air space between the nailer panel and the foam. Using continuous drip edge vent and continuous ridge vent eliminates ice daming as much as any system can without the use of radiant cable. Generally speaking the bottom side of the foam panel (assuming thickness of 4" (R-23)) never gets cool enough to become a condensing surface. This product can be mounted on ply or OSB decking or use structural T & G decking for a nice interior finish without drywall.In response to your theory regarding condensing surfaces, it helps to picture a cross section of your wall or roof structure. On the interior you have a temperature of say 72 degrees F. On the exterior you have a temperature of say 0 degrees F. At some point in that structural section the ambient temperature and the RH intersect to identify where condensation will take place. I think the idea is to design the section so that the intersection (call it condensation point or plane if you wish) occurs within a material that air, vapor or moisture cannot penetrate, such as rigid foam insulation or possibly dense pack cellulose.This all seems like very basic science. If I'm missing something here I'm sure the experts will be glad to point it out. I too am interested in learning more from those who know.EB
*Hi Mongo,Your proposed approach seems way more complex than is desireable.What about SIP's for new cathedral roof construction? Will your codes guy allow that? Barring that, I would ditch the multiple layers. Just make the rafters as deep as you can, lay in a plywood or iso board vent channel, rock or T&G the ceiling, dense pack, and be done with it. The dense-packing will nearly eliminate air exfiltration, and eliminate the condensable surface, same as it would if you didn't have to build the vent chute. The upper piece of plywood (the roof deck) is outside of the equation, as it is theoratically a free floating exterior structure. That's the concept behind the vent-chute requirement in the first place: the roof deck is awash in exterior air, isolating it from the thermal barrier.Iso board is expensive. When used on the inside (over rafters or walls) it makes acheiving high-tolerance finish surfaces a pain in the ass. I could see using it on the cold side to create the vent chute, since you would have to buy plywood anyway, and you might as well buy something with higher r-value. Also it may ease your mind about the condensable surface issue. Since any air-borne moisture that might possibly make it through the dense-packing would wind up on the warm side of the iso board, there would be little-to-no chance of condensation. The negative aspect of iso board on either side of the cells, in my opinion, is that you slow the rate drying via adsorbtion (diffusion) when conditions on the iso-board side of the thermal barrier are drier than they are on the non iso board side. I'm convinced "vapor" barriers do more harm than good. The air barrier is where it's at.Just my thoughts.Steve
*The location of the dew point in a wall is very often figured incorrectly into where and why a part of a home starts to rot from moisture build up....As Steve and Fred point out along with a local builder, the air movement through a structure is what it's all about....And in the air flow their are all those lobsters with all their moisture....the trick is to not create lobster traps where you don't want all those lobsters hanging out destroying the place...After all they are at their best at the bottom of the ocean or in a pot on your stove.near the lobster infested streamside,aj
*Joe....Time to Barbecue some of these lobsters....Turn up the heat around here will you?!My Lobsters are gonna get you some day,aj
*......here's the part I miss.....why don't I want a vapor barrier on the warm side ????even IF the VB does nothing else, it still acts as a very good AIR RETARDER, and it definitely keeps the warm moist air within the envelope until I handle it and move it out via bath fankitchen exhaust fanexterior doors opening & closinginfiltration in the real framing world...next (that last was a question , remember?)...here's my EVOLVED cathedral ceiling from <<>>blueboardfurring 16" OC.wiring behind the furringpoly vapor barrier behind the wiring1" iso foil faced (R7)18" cells tapering down to an energy heel at the platewith foil-faced iso layers if I run out of room with my energy heelPropa -vent foam baffles venting the bottom of the roof sheathing<<>> toShingle Vent II ridge vent...Roof sheathingRoofing....thats my story & I'm stickin to it.....and that evolved about 15 years ago....not a dead customer yet...b .....Kermit
*Mongo - I like your approach (which is why I'm in the midst of excuting a similar scheme as a retrofit) but offer two suggestions. A single layer of foam on the rafters should do nicely - say 1 or 1.5" polyiso - the kind used for roofing. Purposely sheath with 3/8" gaps and foam away. Then use the thinnest, cheapest, and most permeable "chutes" your building inspector will accept instead of the upper layer of foam. Blow cells through holes or slots in polyiso, foam holes, and rock away. I think you are justified to worry about exterior foam being a double vapor barrier.By the way - I believe they are using this basic approach on a large development near here - with Lstibruek's input and the building inspectors blessing on no vents - and no plans to make attic living space! Just easier to get a good air seal at rafter plane and permits ducts in attic - all inside the thermal boundary.
*Consensus??? On this Board??? You got to be kidding???In the last nine months I can't think of a more vigorously debated topic than energy management with its sub-parts of insulation, vapor retarders and venting.Over the years I've seen methods and materials come and I've seen methods and materials go. It is almost like a big record revolving on the turntable. But, when all is said and done there is no one correct way to build a healthy house that is also energy stingy. Nor, is there only one isulation or venting schedule that is appropriate. In fact homes can benefit from using a couple types of insulation and venting.So, the two biggest factors in my mind are: a)Local practice and acceptability and b)Saleablility both to the original owner and resale. These two will vary a great deal around the continent.I admit it is fun to "discuss" this subject. But in most cases it is a lot of passion that could have been better used to promote someone's love life.
*Having read volumes here about cells over the last few years the major point stressed over and over in favour of cells is it's ability to absorb moisture and then dry out by diffusion. No foam or poly should be put on either side or this single most beneficial characteristic is lost. If venting shutes i mustbe used with densepack cells, why not something inexpensive like pegboard strips up against 1x2, which will still let the cells diffuse through the roof if needed???I developed my own "sandwich" some years ago using a pressed f/g board called Glassclad( now unavailable) that had one Tyvek type facer, which I cut to fit between rafter bays and finished off the bay with f/g and a vapour barrier.. . but this was a system made necessary by the characteristics of f/g.Gene Leger has mentioned data that shows that in a i well sealed houseair locks entrances are redundant. In email correspondence with me Gene also agrees that in a well sealed house, seperate combustion air b mustbe provided for combustion fuel appliances(Furnaces), and that relying upon other household air is not sufficient!Thanks to a tip from Gene I am also in possesion of a paper called "Ten Years of Canadian Attic Research" by Don Fugler,P.Eng, senior researcher in the Research Division of Canada Mortgage and Housing Corp. The paper was put together for presentation at the 1999 ASHRAE meeting. I'll quote (without permission) from the preamble and conclusions sections"The research team conducted tests in houses in several distinct areas of Canada. It was necessary to develop a test protocol for attic air tightness and airchange testing. The research project compared the performance of nominally identical attics, one of each pair with full code required venting, and one with all intentional holes sealed. Results showed that ventilation plays a relatively small part in the control of attic moisture and temprerature but, converesely, rarely provokes major moisture problems. This suggests that there is no significant advantage in changing current Canadian attic code requirements, except perhaps by allowing more flexibility in venting design." While the study goes into specific detail for test houses on each coast, in Alberta and in Ottawa the overall conclusions were:1)" Natural ventilation of attics is largely dependant on wind speed and will vary significantly due to local wind shielding. The effects of attic ventilation on attic wood moisture contents will change from one climate to another. In some areas, primarily coastal, lower attic wood moisture contents may be achieved by minimizing attic ventilation rates."2) "Minimzation of heat and moisture flows from the house to the attic seems a prudent way of reducing ice damming and attic moisture problems." "(houses with high indoor relative humidity showed higher attic wood moisture contents)"3)"Despite the above conclusions, there is no compelling case to be made for reducing code requirements for attic ventilation of new homes. However, codes should permit some flexibility in design to allow alternatives ih controlling attic moisture levels."-pm
*Mongo,I am also doing the "no vent" thing on a cathedral ceiling. At first the inspector said that vents were required. I detailed my plans for DP cels in the ceiling and my overall air sealing plan (much of which I learned here) and he agreed to allow it with an Engineer's approval. He actually seemed impressed. Maybe you've already tried this route; I just thought I'd mention it.Jerry
*First, thanks to all who have responded...I appreciate all input relevant to the topic.I can use SIP's (good point) in new construction, but I'm also looking for a solution to use in both new and remodels. Bill, I've never DP'd cells before...wouldn't the "thinnest, cheapest" chutes (if you're referring to flimsy foam or plastic channels commonly used with FG) get crushed in the process? Now if that's your intention.... Or, are you recommending I make a viable channel, but make it as inexpensively and as "permeable" as I can, a la Patrick's pegboard offering?A friend reported that one of our code officers actually pulled out a section of soffit vent on one of his jobs and fished a wire up the chute to ensure it was intact...that's what I'm dealing with. That's a red tag I want to avoid.I'm getting a bit closer (not to Jack's stream), thanks again to all.
*Here's another one: Be sure to know what your local building inspector's opinion is. You don't want to get into a philosophical discussion of relative humidity when your trying to get a final!
*..actually Mongo... i fibbed....i don't use PropaVent (it's almost a generic term)...I use DuroVent..because of the flimsy nature of Propavent (can be crushed by the insulation)Duro Vent is basically the same except it has egg crate type buttons molded in to prevent oilcanning (crushing)...if I have a void above my insulation level , I only use the Durovent in the energy heel area.....here's the next part I don't get....if I have sealed off my attic area from the living space /conditioned space envelope....which I do very concientously.......what is wrong with venting my attic.....given the primary problem is not wanting to introduce moisture laden air.....BUT i'm not I'm venting with winter air, with a relative humidity below that of the hosue structure......and in the summer, I'm ABOVE the dew point so I'm not going to have a problem there....Am I getting beat up because SOME or A LOT of other houses dont do as good a job and consist of FredL horrible examples ?????ie. does my strategy work or am I getting thrown out with the bath water?b ....enquiring frogs want to know Kermit
*Hi Mike,>>why don't I want a vapor barrier on the warm side ????<<This depends on your local climate. If you are an all cold or all warm climate, in theory the vapor barrier is useful. My read on it is that it will do less harm. And if the warm side is flip-flopping with the seasons, than part of the time it's on the wrong side of the equation.So what's the harm ov a vapor barrier in an all-cold or all-hot climate? Say you get a puncture or two in the vapor barrier or the seal around the electrical outlets and such eventually opens up. Then you've created a spot where air-driven moisture can pentrate into the framing cavity and point-load an area with moisture. OR say you develop a temporary point source exterior leak, such as a flashing failure or wind-driven rain, or ice dams. However it gets in, this moisture diffuses out to a wider area of the wall.Now you've got a soggy wall that has no chance of any drying action to the side that has the poly. Even in an all-heating or all-cooling climate there will be times when the RH in the surrounding air on the vapor barrier side is low enough to promote adsorption (drying via diffusion). Why block that possibility when you can air-seal in a way that doesn't?Steve
*That is a rigorous inspection. I don't thing the chutes I've bought and used in the past would crush but maybe they would. I wondered about some corrogated cardboard ones I'd seen; wondered if a 16" strip of corrougated "v"ed in the middle would work. (several dollars for 4'X8' sheets) Installing spacers and hardboard seems like too much work.Rather than cutting spacers and two furring strips per rafter wouldn't it be less work and little more materials to simply double sheath roof - like minimum 3/8" on rafters, 2X sleepers, and your choice of sheathing for top - (I like 5/8 for nailing shingles to - some probably would use the 3/8 if it met code)?
*Eric M. See article Drip-Edge Vents in chapter 23, Attic Ventilation, of my book, _Complete_Building_Construction, 4th Edition,* published by Macmillan. The only drip-edge vent Iknow of that works is the ComboVent.Jerry. Glad you succeeded with the building inspector. The 4 model building codes do not prohibit hot roofs or unvented attics. All these codes have an Alternative Methods and Materials section. But you must satisfy the building official tha the alternative works. GeneL
*By golly I was wrong, you can get a consenus!The later posts show that as Mr L points out thinking is evolving. Also, it has been pointed out that the final answer is what the local building department and owner will accept. So, the consensus is: Whatever you, based on your research and applied to the current structure think is best use it. Subject to the inspector's approval.In my experience how the house is lived in is just as important as the insulation/venting method used. For example, during a recent cold snap I happened to have an extra person in the house. This person liked long showers and generated extra moisture in the house. For the first time in the years we've been in the house we had ice on the windows. Now some would scoff at that by "scientific measurement". But, the house hadn't changed; the only change was that the house was being used differently.So, I've used a variety of insulation and venting methods. Can't say that any were any better than any other once how the house was being used was figured in. With one exception: I firmly believe you stand the best chance of having a well functioning, efficient house WITH adequate ventilation of the exterior cavities such as the roof cavity.
*By the way not getting bogged down in structural details is deliberate. If we focus on what we want to get done then a variety of details will get us there. After all, most everyone here has the mechanical skills. What we are after is how to apply them to get the job done.
*Mike,
Joseph FuscoView Image"Whenever, therefore, people are deceived and form opinions wide of the truth, it is clear that the error has slid into their minds through the medium of certain resemblance's to that truth." Socrates
*Fred,
Joseph FuscoView Image"Whenever, therefore, people are deceived and form opinions wide of the truth, it is clear that the error has slid into their minds through the medium of certain resemblance's to that truth." Socrates
*Re the article that Bill cited: (2/2000 JLC pgs 21, 23 & 24) By the way, Mr. Lstiburek also says that he is OK with a "vented attic in a moderately cold or mixed climate." and goes on to say: "It's important to understand that this is a i climate-specific Recommendation."By the way, for anyone who is not up on the "8000 heating degree day" thing, that refers to the northern edge of the continental US (excluding Wash state) and most all of Canada. One really needs to read the entire article to get the complete message.Bill:Where do you live? By the way, thanks for the info on the manometer (sp?)Mike Smith:You really need to read the article as the name of it is "Ceiling Vapor Barrier". And, be ready for some info that conflicts to what BT gurus preach!
*MikeIn answer to your question "what is wrong with venting my attic". . . Rhode Island would be a maritime/coastal environment wouldn't it?? Even the fence sitting conclusions that I mentioned in my post above clearly state:i " In some areas, primarily coastal, lower attic wood moisture contents may be achieved by minimizing attic ventilation rates." -pm
*Billi "Rather than cutting spacers and two furring strips per rafter wouldn't it be less work and little more materials to simply double sheath roof.. . "You can't be serious. I don't know how much actual construction work you do, but the labour involved in "wacking up" 2 furring strips per rafter (no spacers required)and, to use my pegboard example, gang ripping mutiple 4x8's on a table saw, and then tacking them into place would take 1/4, or less, the time to sheath a roof and place sleepers, not to mention the comfort and safety of working inside, and not out on a roof, and of course the $$ for the material, and possible upgrading of rafter/truss to take the extra load. . . and what about fire protection?? Doesn't thati double roofneed extra detailing??Besides, the i double roofdoesn't vent the attic space. Any moisture from below will just condense on the underside of the lower layer defeating the supposed intent of the vent shute!!-pm
*.......Joe...serving on many boards and committees over the years, I would have to agree with you...the English language is a terrible way to communicate (as are all languages)...it just happens to be the way we've chosen at this stage in our evolution....I've always found that most people have MORE in common than they are willing to admit.. and if you can get by the preconceived notions and abrasive personalities (not that we would be describing you and me now ) ...if you can keep a focus it helps....speaking of abrasive personalities...Joe Lstiburek did a nice article in JLC.. really gave me a lot of hope that we can arrive at consensus here.....there was another good one about Tyvek, Typar and roof felt..b back to this thread...I have to say that a lot of my negative reaction is to being told how stupid I am.... and how I'm endangering my customers...look, this is a group of pro's.. we all make our living doing this day in and day out... we don't knowingly endanger anyone... and I think (and Hope ) that merely by participating in this thread we are trying to arrive at a set of "Best Practises" that we can take with us...we've all been called in as experts by our brother builders to help them with a problem... we've all found the terrible existing conditions and developed effective solutions.......most of this stuff ain't rocket science.....I look at DP ( that jargon threw me for awhile ..Dense Pack) as another tool in my arsenal.. so is venting.. vapor barriers, air retarders... AND CUSTOMER EDUCATION..kind of like Armor taking credit for all victories,... it's a Combined Arms Team with contributions from all of the services that gets the job done...any one of these strategies can be easily overwhelmed (and has been) by customers not doing the right thing...long showers with the fan OFF, pulling out the vapor barrier in a crawl space because it was dirty....hooking up another combustion appliance to an existing flue.....not getting a roof repaired until everything was rotted out...so please. ..spare ME the lectures... I'm looking for a dialogue, if I wanted a lecture I'd pay for one....b you croak first, then I'll answer.....,Kermit
*You may be right about labor for you. I'd rather put down (than up) one furring strip and nail down (than up) full sheets. The difference in cost between hardboard and 3/8 sheathing for 40 sheets (my house) delivered to the roof seems small compared to cutting those sheets and carrying them to the attic. But every situation is different and I could construct a scenario that would make your position make sense. I respect your view but I hope you'll allow that your approaches might not be the best for everyone in all situations.But if it's going to condense on the inner sheathing level, why wouldn't it condense on the bottom of the chute? Besides, in the system described, I'm confident that it is well enough sealed and insulated that there won't be moisture laden air - basic approach being solve the problem at the source rather than treat the symptoms of lost energy.
*Mike, I agree with you in regard to the difficulty in pulling anything definitive out of most papers published on this topic.There are too many variables to give a concrete answer...climate, individual building techniques, homeowner lifestyles, etc.Most any paper that I've read can be slanted towards the reader's goal. You want to vent, you'll read that the writer was hinting that venting is required. You want to seal, you'll see a thread of that as well. Technical papers need to be read as a whole, parsing or taking segments out of context can be very misleading.You know how you build. You can't be in control of a customer tinkering with your efforts down the road. That's where educating the houses inhabitant comes in to play. Knowing that they have a concerned builder will hopefully result in them contacting you for consult should they consider and modifications to the house in the future.I, like you ( I think "you") am looking for a decent conversation that will hopefully clarify the ideas and theories behind a better sealed envelope. I know how some posters support this idea, I know how some vehemently oppose it. However, I'm still looking forward to an issues discussion, free of the typical degradation that occurs whenever this topic comes up.I can research and read on my own, which I have been doing. I would, however, like to use this forum as an open research tool as well. I'll then form my ideas on how I'd like to see envelopes built and, working within my inspector's parameters, my abilities, and with the inhabitant's blessings, proceed onward.
*Fred giving a lecture with Joe in the audience....Now that's one for the record books!!!Need some Barbecue sauce by the stream,aj
*........back to basics..We always furr our ceilings....just a regional habit...but it allows me some design latitude for running wires for surface mounted lighting...and if i want a track or a fan or a large chandelier, I can screw a piece of 3/4 ply to the truss bottoms and pull my wires thru... so generally speaking, 90% of my wiring doesn't penetrate the heated envelope....I also do a take-off on the GeneL thing.... other than bearing partitions, none of my walls go to the rafters or trusses... before we put up partitions we put up 6 mil poly and then furr it.. then we build our partitions , the poly laps the poly on the walls and we guard the penetrations...If I've got a space problem (say insuffcient joist or rafter depth) Then I put up 1" iso -foil face before we put up the poly and furring......now I'm not relying on 1/2" blueboard to hold up the 18" to 24" of cellulose...we prefer cellulose... its been our main go-to since 1978.. but we'll also use fiberglass if the circumstances warrant it...there is no connection and no short circuit between our heated/ conditioned envelope and the vented space under the roof sheathing....we don't use strip vents for our soffits, we use fully ventilated vinly soffit, and most of the time it's between 12" and 16" wide...we use poly vapor barrier as our first line of defense to control any moisture trying to get from in- to- out, Since the poly is on the warm side, it is not a condensating surface, because its temperature is above the dew point...the only thing I've ever seen below the dew point in any of our houses was the occasional corner of a window....b if there is any moisture in the attic venting space ..and it is slowly being released by the cellulose insulation acting as a diffuser and my Winter design relative humidity is say 15%, then that moisture is going to be removed by the air flowing thru my vent channels and out my Shingle Vent II ridge vent.....It is not going to sit there in the dense pack and try to figure out how to get thru my roof sheathing, Roofing felt, and asphalt shingles....conversely.... if I'm going to do a dense pack solid fill.. ten I've got to make sure that I DON'T SATURATE the dense pack by controling the moisture within the comfort envelope...so , near as I can tell, either method, requires control of the moisture within the comfort envelope and I don't see what the big controversy is....If you want to move on...(or not)....what about the walls?b lets talk about the walls...I'm assuming that most of the problems occur thru the ceiling.... but we can't ignore the walls, cause they have their own set of problems....major can be rotting the framing ...secondary is peeling paint and efflorescence of masonry.....
*Mike,
Joseph FuscoView Image"Whenever, therefore, people are deceived and form opinions wide of the truth, it is clear that the error has slid into their minds through the medium of certain resemblance's to that truth." Socrates
*Call me an educated customer (or rather a "becoming educated" customer). I readily admit that I'll probably never build for income or occupation. What I do, I do on my own home because I love doing it. But, as was pointed out, the professionals build what the customer wants (or allows) so I guess in a way I'm equally influential in the debate.I just want to make one comment about humidity and the living space. I've been reading the notes, and the studies and the books along with everyone else. In particular, is the recuring theme of "reducing the indoor humidity" and how reducing indoor humidity reduces humidity build up in the roof space. I don't know about the rest of you guys, but I like my indoor humidity. It's comfortable and it's always higher than outside (even in summer in this climate). To suggest as the studies appear to, that one of the answers to my roofing concerns is to reduce the indoor humidity flies in the face of what living in a home means. I may as well shut the heat off, wash and shower outside and keep desert cactus for houseplants. All of those would greatly help the moisture levels in the roof space and surely add to the life of the building, but that's not the kind of house I'm going to be comfortable in.I don't see reducing indoor humidity as another tool in the move towards a better roof design. I see better roof design as tool in the move towards higher indoor humidity.I'm talking about occupied living space humidity here, not roof insulation space humidity. No arguements from me about the need to keep moisture out of the roof space.Mike, I like your furring over poly approach. Particularily the ability to string the electrical without punching it in and out of the poly.
*.......damn Scott...you forced my hand...I was going to sneak up on that one....look , I inspect all of the houses I've built and I've got them out tere from 1975 baiscally with these evolving control systems.. if i had started out as a builder I would have made a lot of nasty mistakes, but I didn't , I was the 140 lb. guy who always got the short straw to crawl where grown men feared to slither...in short i got to witness a lot of the horror stories FredL and Steve Zerby have been describing... we were also pioneer solar guys, with RESERVOIRS of 10,000 gallons of water in the crawl space or cast-in-place stand-up tanks in basements... and indoor swimming pools ...some of the things they're describing , I've seen and they do make me shudder...but most of those things are under control around here, mostly by raising the conciousness of the contractors and remodelers ... and most of the progress has been successfully handled thru venting strategies.....b PLEASE... I know, its not perfect..But its a hell of a lot better than say,... 1980I think we're here to fine tune some of the strategies, at least that's why I'm here. to learn from FredL, Steve, GeneL, JoeF,Scott, Andrewd,PatrickM, Mongo (shut up AJ, don't interrupt) and anyone else who wants to jump in..The biggest problem I find when I get called into houses now is that they have the relative humidity TOO LOW, The furniture is falling apart, the trim joints are all wide open, the handrails are loose, one of the reasons 6-panel molded doors are so popular here is that contractors got tired of getting call backs about the real wooden doors opening up..Most of the time I recommend a humidifier with a 5-10 gallon reservoir......whoops...gotta goI'll relate one of my favorite horror stories...b
*..........anyways...We are all concerned about our customers...lets see..build or remodel a structure that will perform to their specs, that will be healthy to live in, that they can reasonably maintain, that will be comfortable, economical to heat and cool, that will look and feel and be aesthetically pleasing, and be psyhchologically healthy..(no dark caves, maximize natural light)so, watch out for combustion products,radon (yeh, I know )leadmolddustand the proper HUMIDITY level, say 45% to 55%.anything lower and they start having health problems, breathing, more colds because their mucous membranes are dried out, their furniture and wood productgs start to suffer...OK..true story..10 years ago a contractor friend had recently built a small cape, the Owner was complaining about the workmanship, the house was falling apart,...big gaps in everything, ..this guy has one of the best carpenters around as his leadman...no way would this kind of workmanship exist on one of his jobs...It was late winter (March)...we went in and 1st thing I see is a wood stove cranking away, the house is dryer than hades..we go down in the basement and I ask him what size joists he installed...2x10's 16"OC..so we measure a couple joists...."What size where these when you installed them?" ----"same as ever..9 & 3/8" "Well they're 8 & 3/4" now" I said the Owner was right , the house is falling apart, but it's that wood stove that's doing it....talk to him and get a humidifier installed..(meantime I measured the living room with my sling psychrometer...10% relative humidity)So, here is a good builder....vapor barrier under the basement slab, vapor barrier walls & ceiling, vented soffit, vented ridge...not an excess moisture problem in the structure... and the Owner needed some guidance...now that same house is going to have mold in the closets in August..just like every other house on the water, except the ones that have air conditioning....but that moisture is not going to have anything to do with vapor barriers, or air retarders, or vented soffits, or vented ridges...and it has nothing to do with a vapor barrier in the crawl space, or under the slab.....it needs dehumidification.....I wish there were easy answers....but I don't think there are..I do think that we can come up with a laundry list of first aid and long term care...kind of like the old Red Cross training...."first clear the air-ways, next stop the bleeding"b Hope we're all still breathing..
*Right, so what then, if we seal the ceiling and walls so well that it starts to condense on every window surface? How do we deal with the unreleased humidity?
*"I was the 140 lb. guy who always got the short straw to crawl where grown men feared to slither"Chuckle, chuckle. I spent one summer of my youth as a gopher for a insurance construction company. I was the 90 lb guy who always got the short straw, not the least of which is because I usually volunteered and didn't really mind what the work was. Still the best summer job I ever had, with a decent bunch of guys with good work ethics and skills. I think it also says something about the consumer/builder mindset here. New construction is quick and cheap (and crappy) because the customer doesn't want to pay any more than he has to, but when it comes to insurance claims, the insurance company is footing the bill and now the customer wants nothing but the best (in his otherwise cheap home). If you don't provide quality repair work, neither the customer or insurance company will come back knocking for more business.Now maybe it's the kind of work those guys specialized in, or maybe it's the climate here, or maybe I just never bothered to notice, but I don't recall a single case of water damage due to roof failure (vented or otherwise). We did plenty of shingle repair (after storm damage), and water damage (mostly flooded basements) and the occasional fire (combined with water) damage. I remember one particularily sad case of an older larger historic home which had a 3rd floor toilet crack while the owners where on holiday. Antique furniture veneers peeling and stained, buckets and buckets of plaster and lath to haul out. Yuck. I'll never take a vaction again without first shutting the water off at the meter! But nary a humidity in the insulation problem to be found (except for one house trailor - which I don't think counts). In fact, even wood rot is an uncommon problem. I would even go so far as to hypothesis, that as long as you keep the rain off, between the dry air days and the cold, things stay pretty well preserved in spite of any attempt to improve the process. But that's just an observation in my climate and as I say, the company I worked for may have had more specific guidelines in what they choose to repair. Or maybe roof humidity damage isn't classified as insurance work (although customers usually find a way to justify fixing ANY damage when they have a valid claim)I have to wonder if the vent/no vent discussion even HAS a single overall best method. Maybe instead of trying to answer the generic age old question, what's really needed is a flat out discussion on something more specific like "what's the best way to prevent air and moisture movement between the living space and the roof space?" I'm sure there's lots of useful information to be shared on this detail without having to throw in more "buts" over climate, venting, moisture sources, living habits, etc.
*Mad dog,Sure the unreleased humidity has to go somewhere. You could probably argue that the energy savings of sealing would offset the cost of a dehumidifier or air exchanger (or not). You could also just stick the equivalent of a bathroom fan or vent through an exterior wall and pass it outside. It sounds crazy, and I as a customer would never accept it, but it's really no different then intentionally expecting the walls and roof to control humidity levels. Same amount of air, same amount of moisture carried with it, only instead allowing it into the interior spaces of the walls and roof, it harmlessly exits to the great outdoors. Personally, I'll be opting for a dehumidifier if it comes to that.
*Well, I just wonder how the equilibrium between getting comfortable rh in winter balances with the condensation problem. If you have comfortable humidity, have you already gotten a condensation problem on your windows, or does that happen at a higher level, thus necessitating some form of dehumidifier or air exchange system? If you end up venting it outside, how do you insulate the vent? (heh heh)MD
*Here's an article y'all might find interesting from JLC. I've used two of the methods he details; foam and F/G, and his so called "plywood gussett buildown" with good results except that the "buildown" is labour intensive even with using the method he describes.It's odd that for a guy who uses dp cells, he still uses poly i vapour barrier.Someone should tell him about the d/wall first without poly and pump in the cells after approach!For those that i need to vent and want to use dp cells he mentions a particular product that isn't easily crushed by the cells!-pm
*ScottGood commentary. . . nice to hear some thoughtful stuff from thei other side.By the way, the strapping over poly to eliminate voids is a basic R2000 detail from CMHC, dating back, oh, about 18 years. :}-pm
*Paddy, I read that a few days back. I emailed the author with a few Q's, I'll report what info I get back.Mongo
*Fred,
Joseph Fusco View Image© 1999"The first step towards vice is to shroud innocent actions in mystery, and whoever likes to conceal something sooner or later has reason to conceal it." Aristotle
*And the saga continues. . .
Joseph Fusco View Image© 1999"The first step towards vice is to shroud innocent actions in mystery, and whoever likes to conceal something sooner or later has reason to conceal it." Aristotle
*Scott you are a man after me own heart. My basic points have always been that there are a multitude of ways to physically construct a house so that it will be as comfortable as possible and that sometimes no matter what you do there is going to be something less than perfect. That doesn't mean there is a problem. It just means that is all you could do under the circumstances. To do more uses a lot of effort and money that could be better spent elsewhere.To amplify on my prior example: An additional person occupies the house, moisture generated by the additional person(even though using fans, etc) raises the relative humidity in the house, the temperature drops to -40C(or F since they are the same). Result, ice on the windows. Big deal? I think not because the ice will go away just as soon as the temp rises. Could one design for the additional moisture? Sure, but why? There is extra cost, and the result might be a "normal" relative humidity that is very unhealthy.One other point. This thread, like those before it, has essentially rehashed each participant's position. Why? Well I don't think it is because anyone is particularly stubborn or ignorant. It is just that there are a variety of ways to solve the comfort/health/energy efficiency/customer happiness equation. I think that each of us has come up with the way that works for them in that market and climate.For me that means a living space that has as small a volume as feasible, a variety of insulations depending on where the insulation is going, lots of windows(even at the cost of energy) and as much ventilation as feasible outside the living space. I also, do not like masonry as an exterior material in anything but moderate climates simply due to the heat/cold sink effects.
*.....when moisture moves thru the dense pack (DP) and diffuses (because cellulose is moisture friendly...or hygrascopic, hydrascopic...one of them., I forget) it will release its moisture to a dryer medium....namely the air....in a dense pak roof...this will be released over time into the atmosphere THRU the sheathing, felt , and shingles...this works great , as far as I know.. as long as the moisture is controlled within the comfort envelope and does not saturate the densepak (DP).........if some shingles blow off, or the chimney develops a crack in its cap, or the Owner doesn't clean out his dryer vent, or one of the skylights starts leaking....and water enters the attic, it will diffuse until the cellulose reaches saturation and the water will flow thru the densepak to the drywall and leak into the ceiling....now you've got a nightmare...no screws on earth are going to hold up the blueboard/drywallif the system we've used for twenty years (and most of the energy concious builders) gets penetrated, the same thing will happen except the water will puddle on the top of the poly and give you some time to come up with a fix...(especially if it's furred)...if its a cathedral ceiling, it may even run out the soffit vents....there is no air space between the cellulose or fiberglass insulation and the poly...there may be a little teeney, tiny , itsy , bitsy, (long live Roseanna Roseanna Anna Danna) air space where the poly is bridging over the edge of the furring... but so what ther is no air MOVING thru that space... my blueboard is detailed the same as the air retarder drywall guys...so unless we're talking about GeneL's put up the entire ceiling BEFORE the partitions then there is no difference ...on the other side of the drywall is the same insulation... and mine is just as deep as the densepak guys... and I don't need 4 pounds per cubic foot to stop air flow.... we're both blowing the same number of bags in the same size attics....any difference ain't worth arguing about......if moisture vapor does come thru the insulation in a vented attic, the air flowing up from the soffit vents will pick up the moisture and carry it out the ridge vents....even at ZERO deg.... the moist vapor pressure moves from wet to dry......Cold air at 15% relative humidity will still remove moisture from air at 60% relative humidity..Ask any skier licking his lips....or any snowfield that never gets above 10 deg. dry air will remove moisture from wet air until they reach equilibrium... ask the nice moist piece of fish in your freezer that you didn't wrap up and it got all dried out ("freezer burn").....so once again ...the sealed ceiling using drywall and densepak (DP) is a fine strategy.....works great....so does poly vapor barrier,, super insulation,, and well designed vented attics, proper design of soffit and ridge vent... with continuos flow,...and I don't have to try and persuade any inspector why he should allow a variance from his interpretation of the energy code...b can we talk about walls now???? Kermit
*
Joseph FuscoView Image© 1999"The first step towards vice is to shroud innocent actions in mystery, and whoever likes to conceal something sooner or later has reason to conceal it." Aristotle
*FredB, Just ensure that the house that safely handles the moisture of two occupants never gets sold to a couple with a few teenagers that like to take long, hot showers. Then the "minor inconvenience" will turn into rotted window sashes, sills, etc, etc.While this topic (like nearly everything else on this forum) has indeed been previously discussed in one form or another, every "no vent" thread has broken down into gibberish from repeated and unrelenting personal attacks.I hate vinyl siding. I hate W2W carpeting. I hate formica. I think there are superior materials to each of these. Now go off and find a thread that discusses these, or any other item that I "hate", and see if I destroyed the thread by attacking the proponents of each material. I skin my cats my way and don't try to enforce my skinning techniques on everyone else.Is "no vent" dangerous, and that's why its detractors are so against it, they are defending the inhabitants' well-being? Do these "defenders" also use products that off-gas for months, even years after new construction? I understand the position of those against venting. However, I don't quite fully understand the position of, the theory behind, and the construction techniques used by the "no vent" camp. That's what I'm trying to figure out here. I don't think that's wrong.There may not be a place for "no vent" in each readers' private constuction world. However, I'd at least like to find out enough about it to decide for myself if it belongs in mine.
*Fred,
Joseph Fusco View Image© 1999"The first step towards vice is to shroud innocent actions in mystery, and whoever likes to conceal something sooner or later has reason to conceal it." Aristotle
*et al,
Joseph Fusco View Image© 1999"The first step towards vice is to shroud innocent actions in mystery, and whoever likes to conceal something sooner or later has reason to conceal it." Aristotle
*...........ok , I guess the attic is settled, Fred & Joe are bored and signalling that it's time to move onwe can do walls now and then I 'd really like to talk about heat exchangers (air-to-air) because that is one of the areas I've got to do a lot of catching up on..b walls....walls ; and more walls..here's my fav:blueboard / drywall (1/2")poly vapor barrier2x4 studs 16" oc with let in steel tee braces in cornerseither r13/r15 dense fiberglass or cellulose blown in after the wall is boarded but before it is skim-coated1" iso foil faced on exterior for R71/2" cdx nail basesiding to suit Owner (siding to suit me would be fiber-cement clapboards)I want the iso on the outside so I don't have a thermal break at my studs and I want my 2x4 @ 16" oc because I get a better interior finish....before the skim-coat goes on we'll also foam all the penetrations and we stretch fit the poly around all the electrical boxes.....b what's your's ?
*Mike,
Joseph FuscoView Image© 1999"The first step towards vice is to shroud innocent actions in mystery, and whoever likes to conceal something sooner or later has reason to conceal it." Aristotle
*Not in response to any specific post above, I just received the Feb 2000 issue of Rural Builder. There is an article "Durability of Energy-Efficient Wood-Frame Houses" by Stephen Smulski, Ph. D (I'm just copying it - degrees don't mean much to me). Fundamental to his premise is the increase moisture problems in houses as efforts at greater energy efficiency have increased.Well, the article is interesting and has some fresh ways of viewing these issues but not a whole lot different than what has been published elsewhere.It does however contain a table of "Indoor Mositure Sources" from a 1988 paper by W. Angell and W. Olson. Sorry I'm not better at deciphering the bibliographic note but somehow sponsored by or associated with the Cold Climate Housing Information Center in St. Paul, MN.The whole table is too long to keyboard here - I'll look for a scanner to use if enough requests - but by comparison (all units in pints of water) to soil migration (up to 105/day), seasonal humidity (64-249/day), storing firewood indoors (400-800 per 6 months), combustion (unvented appliances like kerosene space heaters - 7.6 per gallon of kerosene burned), and back-drafting gas appliances (6720/year), dryer vented indoors (4.7-6.2 per load);mositure from showers (.52/5 minutes), cooking (worse was dinner for 4 - 1.58 with gas range), bathing (tub - 0.12), etc. is insignificant.
*Mike. I don't understand why you would use metal T corner braces and 1/2" CDX sheathing. Simpson Strong Tie warns against the use of their corner braces for anything other thsan temporsry bracing. Long before you start the exterior walls, the concrete footing should be covered with either a difussion retarder or an elastomeric coating before the foundation walls are poured. This provides a capillary break. Note: This must be done even if you cover the external of the foundation with RFBI.Any moisture will by pass the RFBI and enter the interior of the foundation through the footings. Don't use fiberglass or cellulose sill sealers. Use an EPDM sill sealer. It won't stiffen in freezing weather, and won't take a compression set under load. It will expand to fill the openings cuased by warping, shrinkage and settling for years to come.GeneL.
*.......FredL....thanks for your input....real helpful..come on buddy, you know we could learn something from you (i don't want to hear "devil maaaade me do it")JoeF and GeneL....I guess walls is a no -brainer...let your framing dry out before yuo close it upuse a vapor barrierinsulate the hell out of ituse felt or Tyvek on the exteriorGeneL..I didn't know that about the T-brace...my Simpson catalog lists all of their wall brace products as complying with all major codes incl. Dade county and LA..the only caveat is that it is not designed to replace "structural panel shearwall" which i interpret to mean it replaces 1/2 cdx corners but NOT an engineered shear wall...the only reason I use a tee-brace is because I've reduced the racking resistance of my CDX corner by moving it ONE inch away from contact with the stud framing...so this is my attempt to forestall a challenge.. and replace the racking resistance factor...Seal all the holes in the wall so we don't create a path for warm moist air to get in and condense...OK we all agree on that...JoeF...you're stating the same conclusion that most of the studies and my own observations arrived at...take care of all the above details...but WATCH OUT FOR ROOFING, FLASHING AND SIDING AND TRIM...which is a whole topic of good workmanship and deserves its own ongoing discussion..Use the EPDM sill sealer ....that's the pink tough stuff, right? (I was so glad to see that come on the market, the old cellulose /poly ones drove me crazy...So we all agree on that one...You guys got ahead of me on the foundation details...but that's ok...kind of ties in with Bill's post on indoor moisture sources...#1 soil migration#2 seasonal air-borne ...I would guess we all agree on those 2.. and the rest are probably more user /Homeowner specific..Lets decide if we want to talk about walls some more... or jump down to foundation... if we talk about foundation, I would think we should sub-divide it into..SLABSCRAWL SPACEand FULL FOUNDATION WITH SLAB FLORS,, and of course the sub-categories of those 3 divisions...just for starters..here in RI,, there are 2 basic types of stem-wall foundations...and most bldg inspectors will not hastle you if you use either one...12 inch foundation poured direct on undisturbed suitable soil with no rebar10 inch foundation poured on a 10" x 20" footing with 2 horizontal rebars in the footing..both would be 2500psi mixso what is the capillary break going to do for me? this is something I should convince my foundation subs to do????In light of Bill Carpenter's table.. Am I gonna get an appreciable amount of vapor diffusing (same as wicking , right?) up thru the stem wall , by-passing my sill sealer, and getting into my stud wall cavity ?....or we just don't want it in the foundation envelope?GeneL... help me out with the jargon (8 years military and I still don't know all the acronyms) what's RFBI ?(you're talking to the guy who just caught on to DP-densepak, remember?)b ....help out an old frog , trying to learn new tricks Kermit
*Mongo:I think you and I are at least in the same chapter, maybe evenon the same page.As you can tell I am definitely in the "vent" school of thought. However, I don't "hate" any particular product because most have their place. For example, in really cold or hot climates I think the fad of putting brick veneer on is counter to good energy efficiency practices. But, most builders do. Why? Because it is a cheap way of adding "class" to a house. We all make the same kind of tradeoffs. Another example is a remodel in Juneau that a friend of mine is doing. He is using vinyl siding. For him it is cheap, quick to put on thus minimizing the time the structure is getting wet in the rain and looks good. Could he have used something else? Sure. But at a much bigger installed cost and with no appreciable difference in structure life.You have hit on one of the reasons I don't like the "no vent" school. In addition to arbitrarily increasing the structures conditioned volume thus decreasing energy efficiency it usually adds to the off-gassing hazard because adherents to this school of thought usually use minumum conditioned air exchange. We know so little about the long term effects of off-gassing on the human body that I prefer to take the conservative approach by making sure there is more than required air exchange. Does this result in higher energy bills? Maybe. But, crassly speaking, a few diagnostic treatments or days in the hospital are far more expensive.Now I admit my experience is primarily in sub-arctic and mountain climates where lots of time is spent indoors. To those of you in the milder climates maybe indoor air quality and energy costs are more academic than they are for me.
*I work in western Pennsylvania. We have long hot,humid summers and long cold mostly dry winters.I do remodeling on older (35yrs to 100yrs)homes.They are plenty ventilated on drafty days already. There is moisture in the attics. Building additions and/or reroofing requires I consider whats existing.I read the whole other thread and will still vent.Nothing explains how to deal with existing moisture which will find it's way into the attic.Not to mention the extreme build up of heat.I don't see any advantage of non-venting over soffit vents, ridge vent w/baffles, and baffles for airspace for insulation(installed w/o compressing it).In a non-vent system, what would I do with the moisture that WILL be present? On another note, I'm not claiming to be any type of expert, just saying how I did and will continue to do things until I get some unbiased info from an actual authority of some sort.On the other thread, some very misleading info regarding moisture movement was given by a self proclaimed expert, who was pro-non-vent.Ralph Wickland explained the misinformation away saving me from doing so now.Using an example like a drop of water into the ocean as moisture movement leads me to have very little faith in his expertise in ventless building.I normally don't criticize on this board, but if you open your self up as an expert, you better be able to produce the facts.Yours empirically,Jeff
*Gentlemen:1. If the attic is constructed to be part of the "conditioned space" in the house,(such as with a cathedral ceiling) then the roof structure is just another "wall" right?2. Okay, not exactly. Walls don't get ice dams.3. If the ice dam problem can be solved by leaving a vent path next to the decking (sealed off from the conditioned space), THEN it's like a wall, right?4. Assuming all of the above are true, then all we need is to devise a "wall system" that is sealed. I mean REALLY sealed. Nothing in, nothing out; Possibly creating an unconventional construction system in the process. Now it's up to all the combined brain power here to figure out how to construct this new system.Your comments please . . .EB
*......EB... why would we want to invent a new system.. these walls have been evolving in the field for 20 years... myself, I'm just looking for some input from people who have developed and checked on these systems over the years...maybe there's a twist I could adapt ?...but I'm not out to reinvent the wheel....last time I tried that I used 5/8 ply as my wall sheathing (1973)...on the theory that more was better.....There are only 4 ways moisture can get into the wall... GeneL & Joe F have already pointed out that we don't want water wicking up from the foundation, so they want a capillary break there....that's the EPDM sill sealerWater can leak in from above from rain or plumbing, so we're going to watch workmanship, keep our plumbing out of exteruior walls, watch out for gutter details, flashing details, ice and water membrane at the easves...make sure we're not going to create ice damns..Water vapor can be driven thru the wall from the interior thru holes...so we're goint to seal all the holes, and the joint where the shoe meets the floor platform.....Water vapor can move thru the wall if we have vapor pressure , so we are going to install a vapor barrier on the interior, and make sure it is intact...Water can leak in thru the siding or bad detailing around windows and doors, and gable ends, so we're going to watchg our flashing, use Tyvek or felt behind the siding, think about rain screen in some areas or some types of siding...did I miss anything... ? probably a lot....
*Mike,No Consensus yet.The poly vapor barrier is still a bad thing in my book. Even more so in unvented walls than in a vented roof. In a wall that has one side covered with plastic, any moisture that gets in the wall now has nearly 50 percent less surface area through which it can escape via adsorption to surrounding dryer condiditions. This becomes most critical in mixed climates where the drying action flips from side to side with the seasons.Admittedly, poly is probably a necessary evil in an all-heating or all-cooling climate when you have a wall with insulation that is permeable to gross air movement, such as fiberglass, but I see DP cells as a better solution to keeping more moisture out in the first place, and letting out whatever does get in more effectively. So you all can agree that there is no problem with that revolutionary method of wall construction that's been the standard for twenty years, but that doesn't help the people who have rot and mold in walls constructed that way. I for one think there is a better way.Same goes for roof assemblies in my book. Vent them if you want to as a fail-safe moisture dispersion measure and to cool the attic or protect you shingle warranty. But I feel the same caveat applies to the poly vapor barrier. If you cannot stop air movement through the cavity in any other way, than by all means use your poly, but realize that it carries the drawback of restricting drying to the poly side of the cavity. So even for ceilings, again I think the DP method of stopping air movement is a better way, though less critical than in the closed six-sided boxes that make up wall cavities.In mixed climates it's a no brainer to me. In all-heating or all-cooling climates. the crux of the issue rests on whether DP cells really does retard as much moisture migration into the cavity as does a poly vapor barrier.That is what I would like to see some hard research on.Steve
*Eric,I take exception to number three, as would many many people who live near me in Central New York. This has been a horrible winter for ice dams. Conditionas have been perfect: Heavy snow followed by days in the 0-20 degree temp range. There are huge ice dams all over htis neck of the woods, on roffs vented and unvented. Venting will not stop ice dams. Adequate insulation will.On one house I did a lot of remodeling on, there are four different shed roof constructions. One has R30 FG and poly with vents and a sheetrock ceiling, one has R38 FG and poly with vents and a t&g ceiling, one has R19 and poly with sheetrock, and one has R19 with no poly, vents, and a t&g ceiling (that's the lecagy roof). The two with the sheetrock ceilings (R19,R30) have virtually no dams. The two with t&g ceilings have ice dams. The worst one being the R19 t&g with vents and no poly.What I read from this is that the vents are not the critical factor, rather stopping heat loss from air movement and from conductive loss are more important.Also, I drove past a house that had about 500K worth of work done on it last year, including all the siding ripped off, fg insualtion, new sheathing and siding, and the full fg and vent treatment in the attic. It has some of the worst ice dams in town. I bet those homeowners are pissed.What do you think?Steve
*>>why would we want to invent a new system.. these walls have been evolving in the field for 20 years<<Mike, Well, for starters how about because they fail too often. Not always, but often enough for it to be a problem, in my book.Steve
*....OK Steve.....I thought walls were a little non-controversial....but maybe not....why don't you describe the wall construction you use, given your choice...and describe any peculiarities,,, and your reasoning.... ice damns can be a symptom of warm moist air condensing... but they can also be just a simple freeze - thaw cyclethey also tend to build up where run-off and drip can't clear the roof edge, like if there is a gutter system.... or at the bottom of a valley....they can also be a function of a dark roof facing south where the upper roof is clear, and the lower roof is buried in snow, the melt from the upper roof , runs down and to the area that is insulated by the snow and refreezes and the ice damn extends up the roof..ice damns can build just like an icesicle (spell ck>) in reverse...the source of the water is NOT ALWAYS from the interior..anyways... ice damns are not a function of the wall.. they are part of the roof problem and EB , JoeF, and GeneL were discussing b WALL DETAILINGdo you want to back up to the previous sub-category?... or build your wall section for us?
*.......Steve, just because something is vented doesn't mean it's vented correctly....SHED ROOFS are one of the biggest offenders...HOW were they vented? did they have extended eaves with a full soffit vent , continuous flow thru the rafter bays to a PEAK (half ridge ) VENT ?I mean, if someone did a lousy job of a no-vent dense-pak roof, I certainly would'nt stand up and say...."HEY, FredL SEE, no-vent sucks bigtime"Part of the problem is , we can't just pay lip service to these strategies....you have to plan the work and work the plan..(IMHO, of course)
*Steve,The point I was trying to make (albiet unclearly) is that aside from the ice damming, if the attic is a conditioned space then the roof and wall sections could be/should be the same. In a conditioned space attic the air circulates just as it does in any other part of the house that is conditioned. No more or less humidity or vapor pressure than is exerted on the walls throughout the house. Yes, one key to ice damming is sufficient insulation (I thought that would be a given), but other factors outside of vapor barriers and insulation (as you point out)as often as not cause this problem.I guess my point in a nutshell is this. There ought to be a standard detail for new construction that will work for both walls and ceilings assuming the attic is a conditioned space.EB
*Mike, I beginning to see a serious drawback to the lengthy note used to open this thread. If it's walls you want, would you be so kind as to start a new thread on walls? (with a shorter opening line)If you use furring on the ceiling, why not on the walls as well? For that matter, why aren't walls treated the same as roofs. Other than the orientation do they not serve an identical purpose?I'm still perculating over the walls in my house. It's currently gutted and waiting to be messed with. I have to deal with exsiting exterior walls, some of which will some day become interior walls and some of which are going to be "thickened" on the exterior. And then there are yet more walls which will be built from scratch (new construction).My ideal wall would look something like this (from exterior in):Exterior finish (mud and wire)felt1/2 sheating (exterior working surface)1.5" rigid insulation5/8 structural sheeting (or existing 1" planking in old)4" or 6" studs, 16" or 24" oc(depending on new or old)Cavities filed most likely with fg1/2" rigidPolybubble foilResiliant channel1/2" drywall1/2" blue board (does it come in 1/2"?)plaster skim coatI call it my dream wall because somewhere between cost and reality is who the real wall will built. And to be honest I don't really see anyway out of the electical box nightmare that this would create.Sound control is high on my comfort list, hense the resiliant channel, and to a degree the double thick drywall. I don't know how easily channel is going to fly over 1/2 rigid and bubble foil. Maybe the bubble foil slipped between the channels instead of under. Maybe the same with the rigid.I'm a believer in the concept of bubble foil, although I think the cost is wacked.The idea of even a 1/2" rigid isolation between the stud and the interior space gives me fuzzy feelings, and it takes up hardly any interior space at all. Although it does create a whole new can of worms with the interior finishing.The double thick drywall serves two purposes, sound control and heat mass. When I first took posession of the house I was completely dumbfounded by the size of the monstrous furnace (initially coal, converted to gas, converted to forced air). The furnace is long since gone now, replaced with a boiler and RH. What I realized after hauling out countless truckloads of plaster and lath was that it in spite of the insulating and heating problems, it probably took a long time to heat up the plaster, which then likely radiated it back into the rooms and made the whole setup feel reasonably comfortable and even. I would hope to recapture some of that "low tech balancing" with extra drywall, two thin layers being easier to work with than a single thick layer.On the north side of the house I intend to double up the exterior wall with a a framed up non-bearing insulated stud wall (there are also exterior details which require it to be thicker). I hesitate to simply build up the exterior with the equivalent thickness of rigid (a) because of cost and (b) because I believe the wall should be able to breath to the exterior. Besides, there comes a point where there's just too much foam to get any kind of real mechanical attachment.
*Hi Mike,Glad to discuss with you.I have built many walls the standard way: sheetrock/poly/fg/plywood/housewrap/siding and will continue to build them that way if the clients don't want me to do it my new preferred way which is:sheetrock/cells/plywood/roofers felt/sidingThis is because of the reasoning I stated in the previous post. I'm sure any or all of the ways people have been describing are workable. I personally haven't had any of my FG/poly walls rot as far as I know, but I've read media accounts of it happening on a fairly regular basis. Also, a lot of my work is on older houses (hence the name of my business is Meetinghouse Restoration) FG insultaion and balloon framing are a bad combination. Heat and moisture shoot right up the walls and into the attic. DP cells solve that problem and are a relatively easy retrofit when you don't want to tear open all the walls.Losse blown cells are trouble though, as they don't have the air-stopping property of the DP method.To me one of the overiding principles is to keep it simple. People do things to their house after you leave. They poke holes in the wall, they hire someone to remodel the kitchen, they maybe build a small built-in into an exterior wall, etc. For this reason I like to build the wall in a way that a penetration will not allow moisture to migrate throughout the wall. I can't think of a simpler more failsafe method than my new preferred system. As far as the many-layered approaches being discussed, I'm sure they all add some thermal performance, but at a cost that is most likely not recoverable in the near future. I feel you are better off concentrating on getting a good seal throughout the house and as much insulation at the top of the house as you can cram in. That's the low hanging fruit. After that it gets to be diminishing returns.Steve
*......Scott , If I start another thread just about walls, it will become almost impossible to follow..I'm not going to go back and post sub-replies anymore either, even though I did with Steve Zerby, it's too hard for others to follow, and half the time one doesn't even know that they are being replied to, so ....I'm hoping we can keep this thread linearb linear is easier..about your wall... the electrical devices can all go in a 4" box with a 1" drywall ring or a 1 3/4" drywall ring (assuming the resiliant channel is 3/4")that allows you to securely fasten your box to a stud especially if you use a 4" box with a fastening ear...some will say that you should use a surface mount box... but they're close to ugly...what's with the sound control ? a little overkill?you're exterior is double sheathed and your interior is double rocked...so the resiliant is a bit much, do you live next to an airport, or the cows roaming around make too much noise?If you goto that much trouble with sound proofig your walls, now your windows and doors become major weak points in your sound envelope...think about trading off some wall for an upgraded window ...IMHO, Mike
*Mike,I did the venting on three out of four of the roof configurations.The roof is contemporary style with overhang at both the top and the bottom. Continuous strip vent runs the length of both the upper and lower soffit. Baffles are used to keep the channel clear.The legacy part has the same soffit/vent configuration, but no styro chutes. The failures come on the sections that have poor air sealing and/or too little insulation, and the air sealing seems to be the biggest single factor, as it's the t&g sections that are the worst.The t&g section that I built, with r-38 and poly vapor barrier is pretty leaky. It melts off quickly around the skylight, the plumbing stack and the woodstove chimney (the woodstove is almost never lit).I admit this was before I was aware of the importance of good air sealing. I did not take the care around the penetrations that I would now.attached is picture of the house.Steve
* Steve,
Joseph Fusco View Image "The price of apathy towards public affairs is to be ruled by evil men." -- Plato
*.......FredL... as you point out....walls are different animal than the roof / attic and subject to different forces....generally a higher delta-T...higher moisture vapor levels, etc.I'm content with an R-20 wall under todays comfort expectations and the economics of heating in a 6000 deg/day enviornment...I don't like 2x6 walls because of the thermal break across the studs.....and I don't like 24" framing because I have too much trouble with my trim....I've learned a couple things in some of these discussions...First I may go back to just 15# felt and eliminate the Tyvek...(definitely crossed Typar off my list)..Second, I might move my R7 foam to the inside of the studs... and furr it horizontally @16"OC...I can eliminate the steel TEE let-in brace, and blow my wall cavity before I board... I can also get a channel for 90% of my wiring and switch all my boxes to 4" with drywall rings like I was describing to Scott....I can seal any penetration with canned foam, and tape all my foil joints... and I can lap my ceiling vapor barrier onto the face of the foam before I furr... I may even be able to eliminate some of the electricians plate and stud drilling because he can run horizonatally and vertically in my furring space.....hmmmmmmmHas anyone here run Mass Check? , that is Massachusetts energy requirements based on the Model Energy Code..... I haven't , but I understand that it's comming to a building department/ code enforcement officer near you soon....the point being, the R-value of the wall is going to be imporatnt in compliance...Anyhow.....most wall problems that I've seen and read about were directly related to rain infiltration....which comes back to using good details, flashing techniques (even rain screens with certain types of siding and climates)...So yeh, I'm going to seal and protect my wall cavity from the four directions of attack...below...inside....outside.. and from above.....b How we doing on these wallsare we ready to move down into the foundation area yet....the source of most of the problem moisture ?????
*Eric,Well, there are differences in pressure diferential. It is high at the ceilings, and nearly always pressure from inside to out, whereas with walls it is anywhere from high to nuetral to negative w/respect to the outdoors (from top to bottom of the wall respectively).But I do agree that there is a standard construction detail that will handle both roofs and walls: Dense packed cellulose w/ or w/out vents as the spirit moves you.Steve
*Joe,I find it curious that whenever you feel the need to try and belittle me you think the way to do it is by pointing out that I bought a book to learn more about something that I was intersted in. Where I come from reading is considered a good thing. But then again, you have to have a better than marginal grasp of the english language to take advantage of all the marvelous things that books have to offer, so I guess I do understand your hostility.Steve
*Mike and Scott,I still think you are putting far too much material and effort into the walls and creating a system that is overly complex, yields only marginally better thermal performance, and is more trouble-prone in its moisture handling performance. But I'm certainly not positive about any of it. I don't think any of us are going to be suffering any lawsuits for the way we are building. We all are concientious enough to find a way to make it work for us. But like I said, I hope there is some real research going on w/respect to this stuff.But good luck to you both. Thank God there are a few people on this board who can discuss this important topic without throwing rocks and tantrums.Steve
*Scott. As Fred commented ,you'll gain nothing from the added GWB. In a properly sealed and heavily insulated house there are no thermal swings or overheating from solar. Ergo, there is no need for added mass.The electrical wiring problem is ealily and cheaply solved by using Surface Mounted Wiring (SMW), preferably Electrostrip.See http://www.eanderson.com. GeneL.
*I have followed these discussions for a while and have been thinking and discussing this around here as well...I am seriously thinking about a totally NO VENT roof in a simple gable end, two-story house. I am considering a spray-on product that would be applied directly to the underside of the plywood roof deck. (no I am not selling the product or anything). I am then going to use the attic space as two bedrooms and bath with full HVAC.The advantage of this material seems to be that it minimizes the air transmission from the heated space (air barrier). Seems to me that an air barrier with good insulation value is the best combination. I have not seen much advantage to venting the roof - for either roof temperature or moisture issues...
*Ice daming - I have found that ice daming, as complex is it can be and caused by many circumstances, is usually caused by the eve of the roof and the upper part of the roof having slightly different temperatures. What I mean is in a typical gable roof (good R value, vented, etc...) the eve overhang is the temperature of the outside air. The center of the roof (let's say above an unheated attic space) is slightly warmer due to the heat loss from the living space. On a sunny day, the whole roof wants to get warmer - and some snow melts...The dam is started when the cooler eve area starts to freeze (the gutters don't help this much) and the water dams up and freezes behind.One solution may be to extend the insulation out into the eve overhang. This may keep the entire roof to the edge at the same "relative" temperature - and may reduce the formation of the ice dams... It gets complex due to the need for the soffit vents and chutes... This is where I have been thinking about the no vent roof system and some possible advantages????Wadaya Think????
*Jeff,Who are you referring to as the expert? I missed the thread with that information... I have been considering a no vent system and would like to see his "bogus" claims. Could you also repost or direct me tho the comments from Ralph Wickland... I also live in Western PA (near Greensburg) and have the same concerns as you... I would like to get as much info as I can to make a decision - everyone (I guess myself included) has some bias and some agenda... The vent people want to sell more product and contractors want to do it as always done; while the new product folks want to sell their new stuff, and specialty contractors want to enter the "old" markets, etc....I have seen some good engineering and technical discussions relating to how hot roofs get with or without the venting and about moisture transmission, etc... but think that the jury is still out....
*John,Been looking at a lot of ice dams this last couple of weeks. Ever notice that there is never an ice dam on a vacant, unheated house? What I call an ice dam is caused by snow melting off the roof and re-freezing on a cold eve, as you say. Moisture building up inside the roof as a result of too much interior moisture being funneled into the framing is a different problem.So it seems to me you have two choices for combating ice dams: Heat the whole roof, or keep the whole roof cold. I pick number two. Adequate insulation and air-sealing will accomplish it far more effectively than ventilation. I believe that ventilation can help remove minor amounts of interior moisture, but that it doesn't work very well as methodfor obtaining a "cold" roof.Steve
*Many of you use roofing felt under the siding. Isn't roofing felt pretty much waterproof? Seems like moisture would migrate though the wall and sheathing and condense on the felt, thus rotting the sheathing.I use "breathable" asphalt impregnated kraft paper over the sheathing just because it seems to make sense to me. I feel that it will shed any windblown water getting by the siding yet will still allow the wall to "breathe". I don't pretend to know sh*t about the science of it. Not that anything I built using 15lb tarpaper ever rotted out though, as far as I know.
*........the studies show that 15 lb. roofing felt is on a par with Tyvek both as to resisting the passage of water from out to in, and allowing the passage of moisture vapor.. to assist in drying the wall cavity.... and both products are shoulders above the competition...Steve.... the ice dams you used in you examples were aparently related to allowing moisture into the attic and insufficient insulation in the attic...so, once again that doesn't seem to push one way or the other as far as VENT/NO-VENT...b meanwhile back to walls and then on to foundations...Kermit
*Mike,This is an external ice problem, not inside the rafter bays. The dams are the kind you get when external roof melt refreezes at the eaves. These dams are not caused by excess moisture getting into the rafter bays. No excess moisture is getting into the rafter bays, only excess heat loss via air leakage and/or insufficient insulation. At one time there was excess moisture getting into the rafters and it manifested itself as ice coming out of the soffit vents themselves. I have since mitigated the interior moisture problems. All cavities are vented in the same manner, and the venting is unable to cope with lots of hot air leaking into the rafter bays or not enough insulation or both. The fact that the R19 roof with minimal air leakage is pretty much dam free , while the leaky R38 isn't, tells me that the hot air leakage is a more important factor than the level of insulation.The way I interpret it, is that the vents do an inadequate job of clearing the rafter bays of heat when the load is high, and that the heat load is highest when the ceiling is the leakiest.I'm not saying that the venting doesn't help a little, only that it isn't effective *enough* where there is high heat loss into the rafter bays (or attic).Steve
* Steve,
Joseph Fusco View Image "The price of apathy towards public affairs is to be ruled by evil men." -- Plato
*Well, I did say it was my "dream" wall after all. As for double drywall sound insulating, I don't know where you guys live (acreage in the country? Just kidding, don't start flailing me with where you live!) but I'm just off city central, 5 blocks from the train yard, one block off a major city artery. That means sirens and rail cars at all hours of the night. If you've lived within half a mile of trains, you'd know what I mean.Ok, ok, so it's not so bad that the house particularly requires extra sound deadener (even I wouldn't buy next to an airport), but that's one of my comfy space requirements. High humidity, and low noise permeation. If the neighbors want to crank the stereo, let em. I intend to do the same and enjoy it to the fullest. Far as I've learned about sound control, doubling the drywall is one of the easiest defenses (along with all the other details, air sealing, better windows and doors, yadda, yadda).But as for heat mass by doubling drywall. Would somebody please explain to me why this ISN'T a reasonable approach? It IS mass and it IS in the heat envelope and it IS probably the easiest and cheapest way to add it (without totally redesigning your floorplan). Is it a psychological barrier of spreading it out on the walls as compared to having a single equivalent pile stacked in the middle of the room which throws people off or is there a good physical reason? Maybe I've just lived in too many cheap apartments with noisy neighbors, but I think there's alot to be said for the value of solid, heavy walls. I'm all ears.Sorry, didn't mean to interrupt the efficiency of the building process with things like occupant comfort again. (I don't think I'm ready to move out of walls and on to foundations yet Mike.)
*...SteveZ...I liked the analogy "picking the low hanging fruit"...hell I go for the windfalls too !I never did get too many complaints from unoccupied homes either...what's up with that?.........if I remember from our solar heat days...the average house doesn't utilize the mass its got...so doubling the drywall is just adding mass that you will not recover anything from....the theory was (like in a trombe wall) that the sun would shine thru the south windows, heat the wall, and then when the temp. dropped in the room at nite, the wall would give up its heat to the room...never happened ..if you could get it in you couldn't get it out..and that was sun (read "free") except that it wasn't free, it had huge capital expense, and you had to build in mass inside the living space , so it was space that was dedicated to a single use......what you got ? a 6 month heating season (I usually think of us having a 5 month)... so , you are heating your mass with fossil fuel, so you want the LEAST amount of fuel consumed to maintain your comfort level....you don't gain that by heating up mass, you gain it by heating people...SOUND control is a whole 'nother ball game...go for it..but make some economic trade offs...subtract from your strong parts (the solid wall) and add to your weak parts (windows)..(IMHO)
*Densepack cellulose will make a wall much quieter than one filled with fiberglass and it's very econamical both for material and for labor.....Kiss it, near the stream,aj
*Mike - I think you said that wall construction has nothing to do with venting attics. The other day with a light covering of snow I could read the floor plans of almost every old house around based on the snow melt pattern. And the clearest were the ones with vents. I suspect that the vents further increased the pressure differential between the interior and exterior so warm air is streaming up to the roof deck. Really quite amazing.
*Jeff,
Joseph Fusco View Image© 1999"The first step towards vice is to shroud innocent actions in mystery, and whoever likes to conceal something sooner or later has reason to conceal it." Aristotle
*...Come on Bill..what 's up with that...not to piss you off or anything, but most of what you described sounds like bad insulation or poor workmanship...when I can see patterns on the roof, it usually means that part of the house is better insulated than another part, one area is the stairwell in a Cape,....... you don't say what kind of vents, wether there is a vapor barrier or not....I mean, lets at least find out what is going on before we blame those patterns on DensePak.. how unfair can you be to Steve...(heh)Hey, I'm going to give a prize to the one who ignores the most slights , both real and imagined... you know , turn the other cheek, ahem,Are we ready to find out the things we can agree on as concerned builders, or do you guys want to keep bickering...if you do, you could try using a double standard, like blasting each other on another thread and trying to say something nice about the guy on this one....(new concept)...b Hey, ready to wrap up wallsand then move on to foundations ???
*Mike - you seemed to say that wall construction is not related to attic venting and I was just trying to point out that I believe they are and that one has to treat the whole house as a system. I appreciate you trying to compartmentalize the different components and lead a productive discussion but I don't think the former is good science and I'm saddened the later seems undoable here.
*........OK , Mr. Bill, how is wall construction related to attic venting ?and when you say the worst case was the ones with vents, you still arn't telling us squat... what vents?continuous soffit vents, Cora-vent? Roll -vent?, mushroom vents, Shingle Vent II ?.....s'up?1 1/2 " dia. vents connected to nothing in an attempt to fool the building inspector? If I'm sealing the top of the living envelope , and you are, why do you give a shit wether I vent my soffit and ridge and why do I care if you seal yours off.... we both agree to seal the top.... and insulate the hell out of the space above it... and you're going to dump moisture back thru the drywall... and I'm going to dump moisture into the atmosphere thru my vents.....so on the theory of the glass is half full..... we agree about the top of the house.....b walls...walls... wallsand lets try and stay linear...
*John, this thread is an off shoot of a thread titled"Is Roof Venting Needed" by mauri meere still active Feb 15 with at the time 123 posts.Scroll up or down and set aside some time to read it thru.Ralph Wickland may have posted there or here, I can't keep the 2 straight. I believe it was FredL that I was commenting about,but I may be mistaking him for someone else. Once again, too many players to keep straight.At one point a reference had been made about a book and an article they had written strongly in favor of not venting.The person in question had advocated non venting and used some incorrect "scientific" analysis.Stating that moisture can move from a dry to wet location by the examply of a drop of H2O into the ocean just doesn't cut it.My point was that I came here for newer,valid info.I just read in full an article in the Feb.2000 Journal of Light Const. page 21.Question ...Ceiling vapor barrier Y or N? Short answer for our area(I'm a remodeling contractor in Pgh. and work all around the area)is ;forego plastic and use vapor retarder(kraft-faced insulation or latex ceiling paint).All attics vented or not should have an air barrier((properly detailed airtight drywall ceiling(any climate))The author states he has no problem w/relieving moisture thru vented ceiling. This info for our area cold/moderate cold with 4,500 to 8,000 heating days.Jeff
*Not whining, just stating that if you're trying to advocate non-venting, you'll need some better examples of why it works.No chip either, just looking for info. Perhaps I was wrong, but I read your posts as though you think of yourself as some type of authority on the subject.In general I only respond to posts with info I an sure of, or I pose a question. I didin't come out of nowhere, I fully read both threads on the subject.Not only will I tolerate discussions on various subjects, I hope to learn new techniques every day.I started in the family remodeling business as an early teen, and went to trade school to earn an associates degree in carp./const. tech. at the age of 30.Doesn't sound like someone that's afraid to let their experience evolve, now does it?I'd be happy to discuss the pro/con venting issue, but if you consider an opposing view as "whining", perhaps you should just continue preaching to the pulpit.Jeff
*Did anyone read the answer to the ceiling vapor barrier Q in Feb. Journal of Light Const./page 21? It read,to me, that I was doing good for my area and situation. Latex on ceiling and vents to rid old homes of excess moisture.That and my belief that a wash of outside air under sheathing helps reduce hot spots higher up that may melt snow and cause ice dams down below.Jeff
*Gene,Your link for Electrostrip doesn't work. I did a quick search and found this: http://www.icg.siemens.ca/products/products/c_electrosrtip.htmHope this helps,Jerry
*Fred,
Joseph FuscoView Image© 1999"The first step towards vice is to shroud innocent actions in mystery, and whoever likes to conceal something sooner or later has reason to conceal it." Aristotle
*To All,I've been following this thread with interest (and difficulty ) and it got me thinking about conduction, convection and radiation. I was especially confused about the part radiation might play in attic heating. I found this:Figure 11. Radiation through Piston Cylinder WallRadiationRadiation heat transfer is energy transport due to emission of electromagnetic waves or photons from a surface or volume. The radiation does not require a heat transfer medium, and can occur in a vacuum. The heat transfer by radiation is proportional to the fourth power of the absolute material temperature. The proportionality constant s is the Stefan-Boltzman constant equal to 5.67 x 10-8 W/m2K4. The radiation heat transfer also depends on the material properties represented by e, the emissivity of the material. For a surface with an emissivity of e = 0.8 and T = 373 K (100C), the radiation heat transfer is For moderate (less than 100 C) temperature differences, it should be noted that the radiation and natural convection heat transfer are about the same.It seems that possibly half the heat in the attic would be due to radiation, but would depend on the emissivity of the surface. Does anybody know the emissivity of wood, or what percentage of attic heating is due to radiation?There's more here on conduction and convection if anyone is interested. Heat Transfer MechanismsJerry
*Jerry,
Joseph FuscoView Image© 1999"The first step towards vice is to shroud innocent actions in mystery, and whoever likes to conceal something sooner or later has reason to conceal it." Aristotle
*Mike - I was passing along my observations. To much I read here seems to be based on what people think and have been told rather than what they observe.I stated twice how I think they are related - the air in the walls is warmed and rises through the wall to the attic. Obviously, it will do this unless the top is sealed or the wall is blocked - which fg doesn't do. Even if the wall is blocked at the top, the upper part will be warmer in an empty of fg insulated wall - just under the eaves.The local custom is mushroom vents - some of the most particularily ugly contraptions I have seen. Sometimes a dozen or more. Most of the houses that did not exhibit snow melt or showed less did not have any vents.But the conclusion remains that if you can see the outlines of the walls in the snow melt on the roof in most houses in a neighborhood, there must be some connection.Finally, I have not found the best solutions come from linear approaches, have based my career on looking at planning problems in non-linear fashion, and probably won't change now. Sorry.
*.........Bill, I don't want you to think linear, I was just asking if we could post linear, instead of making replys to posts 20 entries back... it amounts to (here's another anlogy) ...two people having a side conversation while the rest of the group is discussing something else... what they are discussing , may or may not be important, but everyone has to stop and go back and then when the conversation starts up again, its hard to tell which post is being referred to..(JMHO)...b ..to tie into the wall cat.....if you observed houses that had leaky walls, leaky ceilings, mushroom vents, then the topic should be ..b "BAD PRACTISE vs. GOOD PRACTISE = consensus"that's not what is being discussed and anyone reading your post would have thought that you were comparing a well built , well insulated , properly vented, structure with a DensePak, properly detailed structure.....and you weren't...that's not helpful...before cellulose became readily available we were building R38 attics that were completely sealed from the living space with double layer F'glass...we had vented soffits and gable end vents...they worked well, and still do, but that was 1975... and our techniques are even better and the materials available to us are even better...so lets try ad keep this discussion to best practise....and see where we can agree......BTW...cellulose is my first choice , but I can get excellent results with fiberglass batts and attention to detail also ........near as I can tell the poly vapor barrier (or any vapor barrier) is the big difference, we're detailing with a poly vapor barrier, foam around the cracks and holes, and f'glass or cellulose as the insulation... NO-vent is detailing with dry wall and blowing densepak, and says that any water vapor that gets thru is negligable and diffuses and drys out in both directions...Here's one problem...walls are too large an area of heat loss to ignore.....I don't THINK a stud bay with nominal R20 (a 2x6 with DensePak) or a stud bay with nominal R13 (a 2x4 with DensePak) is going to cut it in my climate of 6000 Deg Days....so I have to add a thermal break of 1" foam (True R7)... now I have either R27 (true R7 + nominal R20) or R20 (true7 + nom. 13)... the surface temp of that wall is completely different than the straight densePak... and the ....thermographs of those two walls is literally (well maybe figuratively) Night & Day....If you get into 8000 deg. day ...forget it.. you don't want to be sitting anywhere near an R13 wall when its 0 deg. and the winds blowing 50...So.... I love simple too, just sheathing my wall and boarding it and blowing DensePak has a tremendous appeal..but I can't spec it.... the heating loads and cooling loads just get crazy.... and the comfort levels are too low for my homeowners....if I'm spending money for an R3 window, why would I settle for an R13 wall, or if I spent the time and money to go to a 2x6 wall, why would I settle for R18 /R19 when I could have a true R25/R26...Do you guys calculate heat loss for your structures...how do you size your heating equip.????Do you do foundation , floors, walls, windows , doors, ceilings , infiltration, air changes????.....if you do you'll find that R40 to R60 in the attic still leaves an awful lot of heat loss someplace else and a lot of discomfort...then when you start working your cooling loads?????.... it really gets badso what about it, what kind of wall are you going to build and why???
*Mike,We're on the same wavelength for the most part. I can see where in 8000 DD zone you would want more R-value out of the walls. I would think it wouldn't be too hard to do a cost/benefit analysis to see where best to apply your efforts on wall area. Calculate window area as a percentage of wall area , what the BTU loss via the R20 wall area is, versus the BTU loss via the window area, and see how much bang for your buck you can get from a window upgrade and/or a layer of ISO board. My guess would be that windows are the next lowest hanging fruit.Steve
*Scott. "..as for heat mass by doubling drywall." In San Diego in 1979 a conference attendee presented the findings of research into the effects of adding thermal mass to so-called super insulated structures. The researchers found that it had little effect on heating performance. A house with 30,000 pounds of mass had that mass increased by 50% to 45,000 pounds. Although there was a differnce in the performance of the house with and without the added mass,it was a difference that made no difference.(Joe fusco and Fred L may remember William Jame's famous dictum: " A difference that makes no difference is no difference"). The cost of the added 15,000 pounds was such that the payback period was 500 years. I hope this answers your question as to why adding mass in a tight well insulated house makes no difference.However, if you want a wall that approaches plaster then double the drywall. Or better yet inststall FiberBond which will give you additional R-value because of the perlite. GeneL
*Heat mass and heating performance. I think you're missing the point. Or maybe I am.I mention doubling the drywall and in response I get comments regarding solar heating (not my point), heating efficiency (not my point), and cost benefits (I might as well live in a tent and put my money towards thicker long underwear - REALLY not my point).My point about heat mass is comfort. The kind of comfort you get when you've just opened the front door in -40 degrees (pick a scale) to let your buddy in. Now you've just flooded the entrance area with -40 cold air. Would you rather A) go get your slippers and swear about the "drafty old house" again, B) crank up the thermostat to restore temperatures to normal and cook the unaffected areas, C) Let the thermostat crank up the heat all on its own (where are the energy dollars going now) or D) let the walls radiate some heat back into the entrance to moderate the difference. Cost benefit is more than just a dollar value. If I had to cost benefit everything in terms of just the dollar value, I would have saved a bundle by NOT owning a home in the first place. I'm sure there's a baby vs bathwater lesson to be learned somewhere in this thread amidst all the other great information which has been tossed around.Now, I think there's a long underwear sale I have to go to...
*Upon beating and beating and beating the "dead horse" suddenly appeared to be........dead. A tear ....Near the stream,aj
*.......Scott....my only point and I think, GeneL's only point is that you've got all the masss you need to take care of the temporary heat loss you described with One layer of drywall.......if you want the second for sound deadening, go for it ... but it ain't goint to do anything for you in terms of comfort heating, or nothing you can measure or feel... if you do want the sound deadening qualities, make your first layer 1/2" Homasote, (a trade name similar to what GeneL described), you'll get better sound deadening qualities and better insulation values.....and take the money and labor you were going to put into resilient channel and upgrade your windows...and weatherstrip your doors....those are BIG noise transmitters..or conduuctors ...or anyways , they let in more sound than you get thru your walls.......and before you put on your long underwear, take the wedge out of your shorts...b lets be careful out there
*Mike. Thanks for helping me get my foot out of my mouth.You might check the archives to see if I posted anything on a house's time constant.A supoer insulated house achieves a long time constant by laots of insulation and the normal: single layer of GWB, no brick or concrete floors anount of mass in the house. Solar houses, on the other hand depend on LOTS of GLASS and even lots more mass.Scott. In a carefully and thoroughly sealed structure there will be no rush of freezing cold air when you open the door. Indeed, leaving it open for several hours will not cool off the house. No, I'm not putting you on, and I haven't lost my "common sense." My statements are based on my research with real houses in below zero weather. Search the archives on this. I wrote quite a bit about this last year sometime. In those posts I mentioned why in a tightly sealed house air-locks or vestibules are unnecessary. Thanks for your patience. Hope this helps. GeneL
* Fred,
Joseph Fusco View Image "The price of apathy towards public affairs is to be ruled by evil men." -- Plato
*..............OK ....FredL's ‘toon signals that we have acheived consensus on two points now...1st the area above the living space .... some refer to it as attic, some the roof... basically , it's everything above the conditioned space... And survey says.....Seal it off and insulate the hell out it...once you get above the insulation you're on your own, you can vent or DensPak or a combination ... and the other divergence of considered opinion is how to seal it off... some say drywall details,,, some say vapor barrier,,, some say detail both... but ALL say......seal it off and don't let the conditioned air leak into the roof or attic cavity....2d.......walls.....insulate them as best you can,, and don't let air leak into them or rise thru them...And don't let rain penetrate them from outside....again ALL agree, don't let air leak into them or pass thru them from inside to outside,,,,,,....and don't let rain and wind blow into them from the outside....sounds like consensus to me.....tighten them up and don't let them leak.......and dry them out BEFORE you button them up......again we DISAGREE about wether to use vapor barriers or not (but I will confess, this discussion convinced me to move my 1" foam to the interior of my wall surface)....which brings us to foundations.... (and after that , we'll move on to air change, and combustion air makeup, and humidity, and air cleaning)...so FOUNDATIONS... if we talk about foundations , I would think we should sub-divide it into.. b SLABS CRAWL SPACE and FULL FOUNDATION WITH SLAB FLOORS,, and of course the sub-categories of those 3 divisions... this should be going from least controversial to most controversial...????How do you build your slabs......and lets limit it to only those slabs that are going to be the floor in a conditioned space....we don't care about your horse barn,,, even though Mr. Ed does.....MattG... I said somewhere on this board that I thought Lstuburik's article in JLC on Vapor Barriers was very informative and balanced.....sorry I didn't catch that from you earlier....
*
Joseph FuscoView Image© 1999"The first step towards vice is to shroud innocent actions in mystery, and whoever likes to conceal something sooner or later has reason to conceal it." Aristotle
*Mike,I'm curious as to why you are beginning to think about putting the foam on the inside rather than the outside. For the aid in air-sealing? I lean towards the outside rather than the inside because then you've got R7 or R14 of impermeable surface between the wet inside and the cold outside. In the event moisture does migrate into the walls, at least the last surface it's going to hit is still probably too warm for it to condense on. That's assuming cold climate. I foret where you are. Are you in cold, hot, or mixed climate?Speaking of cold/hot/mixed climates, has anyone had a chance to read Listrbek's books on building in these different climates? I was thinking about picking them up and was wondering what anyone thought of them.Steve
*Mike. Re using RFBI on the interior. Don't be surprised if the GWB contractor asks for more money and starts using language you are not familiar with. GeneL.
*.....Steve...after some of the things GeneL said, and the discussions with Scott..and some of the things I learned about 15 lb. felt, and /or Tyvek....I reassessed our SOP for walls1 The building wrap should keep out wind and rain, but should allow moisture vapor to move from in to out..felt and Tyvek do that, 1" ISO doesn't2 I'm loosing some racking resistance by putting 1"ISO on the outside3 When my electrician nails up boxes and drills his wires, it interferes with my insulation and it puts the back of the elec. box too close to the exterior, its a potential leaker of air...4 If I move the 1"ISO to the interior and furr the wall horizontally it doesn't cost ME any more money, because we had to do EXTENSIVE blocking on the exterior to keep from crushing the ISO and provide good nailing for trim and cornice and corners and windows5 if I use a 4" box with a 1/2" drywall collar and a nailing flange, the back of my box will only stick into the stud bay about a quarter of an inch, so I can still get 3+ inches of insulation BEHIND the box6 I can better seal my boxes by foaming around the ISO and lapping my vapor barrier onto the 1/2 inch drywall collar..did I miss anything ????..GeneL...my price from my subs won't change for hanging the blueboard, they've got a bigger target than they did have with my furring 16 OC....just as you sit down with your trades with your drywall details, I do the same with mine.....Steve... went to a seminar /breakfast (free) sponsored by our Lumber dealer...about NOT venting crawlspaces...anyway they were drawing names for free copies of Lstiburek' book"Builders Guide Cold Climate"... so I won one...barely cracked the cover, just got it today, gives credit to GeneL for one of the houses they studied and a bunch of other s I was familiar with....looks good so far...about 320 pages.. good reference, ...looks like a good one ot buy....doesn't seperate Cold Climate into sub-categories though (in RI , we're 6000 DD) he's got everthing from Okalahoma north lumped into a 4500 DD category....b ....now about those slabs........
*..........I CAN tell you this much about the book....FredL is not going to like it , or he already doesn't like it...don't know why....there are lots of illustrations...Like I said, I picked it up today at the lumber dealer, and I've only scratched the surface.....I haven't read the latest version of GeneL 's book, but I would say this is one of those that belongs on every builder's bookshelf..........so me and my guys go to this free seminar, get a great breakfast, argue a little with the guy giving the presentation, get a free book,.....I gotta ask ya...b .....is this a great country or what???
*Mike,I too have heard from contractors that the foam on the outside worked quite well....I asked Listburik about it at a seminar years ago and along with a friend at another business, Alternative Energy systems, they all seeem to say what Steve just said....The foam on the outside will leak cold air in to be warmed (not a problem) and warm air out to be harmlessly out of the wall.Foam on the outside or no foam....then cellulose densepacked between 2x6 24" OC that is strapped with junk grade 2by4 16" OC, then no poly, just drywall sealed by the cellulose blowing process.near the stream and not agreeing with your concensus,aj
*Mongo. The 3 model building codes BOCA, UBC, SBI and the CABO One and Two Family Dwelling Ccde all have a section called Alternative Methods and Materials. These sections same basically, it is not the intent of the code to prohibit the use of alternative methods or materials of construction. But the building inspector has the right to ask you for documentation that shows that the alternative is as good as or better than the code minimum. For example get a copy oif the November/December 1999 isue of HOME ENERGY and show him Joe Lstiburek's article, "Unventing Attics in Cold Climates." Lsrtiburek lives in Westford, Massachusetts (978) 589-5100. He is a registered professional engineer. Hope this helps. GeneL.
*.......aj...I listed 6 reasons why I decided to switch...here's another one..if any moisture gets into my wall, which way do I want it to go...in....or out????I don't think there is a better vapor barrier on the market than 1 inch of ISO, so which ever side it's on is the most resistive to passage of moisture vapor...so BESIDES the 6 I already listed that is the ultimate... with ISO on the inside... I also didn't like the visual of the back side of my 1/2" CDX up against the ISO, now its up against Cellulose or F'brglass...if you want..you could even tell us WHY you don't agree with the 2 points of consensus...especially since I tried real hard not to be the least controversial about them.....b by the bay.....
*Thanks Mike,I understand your reasons for the ISO inside, but looking at all the same variables, I have to say I would still pick outside or not at all. Different strokes. No harm no foul either way.I can never bring myself to get up early enough for those contracter breakfasts they throw around here. Maybe I'll have to change my slothful ways.Steve
*Mikey,...he likes it!!!....Well just know this, that where, not when, your wall leaks air, there will be moisture increases in your wood framed wall...Lobster traps as I call them...because the moisture gets in so easily in it's airborne vaporized state, yet once condensed into liquid form, finds no nice built in gutter system sloped 1/4" per foot to a safe drain area...near the stream letting the leaks happen to the great outdoors,ajI think my lobsters are going to get you someday...
*.....Steve...no harm , no foul, just concientous builders, near as I can tell.....aj. baked stuffed, boiled , or steamed, I likes 'em all....never found any in my walls though...Want me to bring some mussels to Petefest 2k ????, steamed in Narragansett beer????I guess by your non-response , we can move on to slab details...how do you build your slabs , aj....aj.... aj..... stop foolin with that foam, ain't no air commin thru there, pay attention to the thread, man, how do you build slabs for conditioned spaces ????
*Missed a few days and look what happens to the thread! The same folks are as combative as ever and everyone else is trying to make up their minds just what it is they can do to make healthy, economical, esthetically pleasing shelter for people. Which is what builders are about, I think.One comment about ice dams: A few posts back someone said they had never seen one on a vacant, un-heated building. Well they may be uncommon in that situation but they do exist because I've seen them. Ice daming is a bit complicated but in this case I think it is because day heating causes some melting that gets as far as the eaves before freezing at night. Have that cycle a couple of days and a dam forms. Although this may happen on all roofing materials I have only personally seen it on metal and cedar shake roofs. Perhaps the roofing material has nothing to do with it but that is the observation. Comments?In keeping with others:Keeping the volume small, lots of fresh high humidity inside air, venting the outside, and the interior mass high...
*.....FredB...sorry, hope you had fun while you were away..I've observed a lot of ice dams too, not so much around here as in New Hampshire, seems to come down to 2 types, external with the water source being the snow melt, and internal with the source being warm moist air like Steve Zerby and FredL are talking about...The external ones show up more on the south facing roofs than any of the others..b hey what about those slabs ?two types :insulated , isolated, floating slab with thickened edge and slab on top of stem wall extendeing to frost lineboth we do with 2" foam (blue, pink, or green) and a 6mil poly vapor barrier to keepthe moisture vapor from pentrating the slab..we try to keep our main plumbing DWV below the foam and our water supply lines on top of the foam with each fixture running off a manifold thru polybutyleneslabs are fairly straight forward, it's mostly a problem of how to insulate them and eliminate as many thermal breaks as possible without compromising the strength and structure..how do you guys build your slabs????
*Hey folks,I have posted a few mentions about what I am doing now - and haven't heard much discussion along those lines - what about masonry walls???I built the exterior of my house with ICFs - they are a different "beast" (and not an answer to all issues - and they bring out new issues!!) BUT - they seem to deal with a lot of the moisture/vapor issues with the wall systems that you guys are trying to make on this topic.My wall system is simply the ICF form with solid reinforced concrete placed and cured. Rain and other stuff was not an issue during construction - and I don't have to worry about what is happening behind the wall system...I am attaching blueboard to the ICFs directly (on the inside of course) and will be putting a stone facing on the exterior. Wiring was not as hard as I thought that it may be (a router and hot knife worked fine). The hard part is the details around the window and door openings....Later... John
*....John...ICF's are something we haven't used yet...are you using one of the systems that addresses the vermin issue?? Vermin in foam is one of the big nagging questions that gives me pause..What measures did you take to isolate and insulate your slab, is this a single story....or two story...basement slab,, or slab for first floor??
*Mike,We used the ICF system from the foundation to the top of the gable ends. That is a 9' basement, 9' first floor, 8' second floor, and an 8:12 attic truss gable end. The basement is open on one end (buried on the other sides). The interior floors and walls are all framed - we used trusses for the floor systems and standard framing for the walls.We did consider the pest/vermin/insect issue with the foam products - as we did with standard building techniques. We also considered moisture, vapor transmission, sound, insulation, strength, etc...I thought I would add the ICF angle into this discussion due to the recent post regarding a rather complex wall system. I had a friend that used more standard exterior shell materials - and he insulated, sealed, caulked, and covered each one of his joist bays at the outside rim. That and other efforts he did to seal the house cost him more time, energy, and materials than my wall system.What do others think???
*...I guess slabs are a non-issue....isolate & insulate, full vapor barrier 6 mil minimum..b crawl spaces & full foundations, then Air-to-Air or HRV's or whatever the latest acronym is....crawl spaces: if you have no utilities to worry about, full vapor barrier on the floor and insulate the floor,, put the vents in to comply with code and provide access for inspection, but otherwise, seal them upif you are runing ductwork thru, then insulating the walls seems a reasonable choice...need provisions for vermin control.. like Bora-care or Tim-borand if you're using a foam, the chances are its got ahigh flame spread rating so it has to be covered with the equivelent of 1/2 drywall..what tricks do you have for these details?...
*.....in looking for products to insulate the walls of a crawlspace, the best I can find is " Foamglass" which apparently will not absorb water, or support vermin, or need to be covered due to flame spread...but it does only have an Rvalue of 2.85 to teh inch which is hardly adequate..does anyone know of some of the EPS which has been firetreated and vermin treated? costs? R-value,,
*The Rastra/Sempo ICF's are made of styrene foam beads bound together with Portland cement. The fire resistance is phenomenal, 4-hour rating on completed assembly. I think the Portland discourages most vermin, including termites. I don't know if the stuff is available in flat sheets, but it seems like the king of ICF's. FHB mentioned them in an article awhile back. My back issues are far away, but the R-value per inch is probably listed there. You may want to contact the mfr. for any leads on flat sheets.From FredL's posts, I get that one wants a capillary break between any soil-coupled masonry and interior wood. I have worked on a place in dry Colorado where the corner studs had rotted for two feet above the treated sill. Even though the culprit was bulk water, it did wick up from below.Bill
*...William Brennan... et al...have you got anything else on that.. thta looks very promising... costs? thickness, sizes,, or a link?...interested in FredL's capillary break DETAIL..but who's to say...he's deleted everything except his cartoons......gonna have to start doing screen captures of everything he says so I don't lose it...
*I, too, would be interested in a discussion of capillarity as it relates to the intrastructural interfaces. Please pass the water.
*........yeh , Ralph... whatever you just said ... that 's what I want to hear about.....Hey Freddddddy! get over here ya big lug.. and tell us about capillarity ...hmmm... is that different when the footing is below the watertable...can we use the radon mitigation tubes as vacumn cleaners???
*As vacuum tubes? Boy, I'll bet we'd have a building envelope that really sucks. Especially if we could develop a way to hook them into a whole house vacuum system. Radon, dirt, moisture and venting problems solved with the flick of a switch.
*Mike, Ralph, Check out Gene's post in this thread, #36.
*...Mongo...went up & reread Gene's post #136, which was a reply to your #55, ...I don't have Lstubireks article and I don't follow the point o f Alternative methods... I'm happy with the current standard of .25 Air Change perhour and I do understand that that converts to 200,000 cfm / day in a 3200 sf house..if I'm doing that mechanically I can control it, and if I find that 100,000 is just great for that family in that house.. ethen they can control that too..but if I don't design for that standard ,, I don't see how the occupants have control of anything...I like fresh air and healthy humidity levels..and I don't see where trotting out an example of LA smog is conducive to furthering the discussion...Gene's book "complete building ' construction" doesn't address ventilation of the comfort envelope, nor does it talk about fresh air.. so I don't know what Gene's recommendation is about fresh air, humidity levels, or design criteria for those in a modern house..Lstubirek "Builders Guid Cold Climate"says 10cfm to 20 cfm per design person and then converts it to per bedroom which at the low level is 30 cfm for two bedrooms up to 60 cfm40 cfm for 3 bedrooms up to 80 cfmand 50 cfm for 4 bedrooms up to 100 cfmso, there's another source.......I tried to post this earlier ,.... but I got timed outb ..we have met the enemy & he is us...Pogo
*.... boy this is pretty lame when you gotta revive your own threads...b OK... we ready to list all the things we got consensus on??Survey says!..........maybe FredL can state all the things we HAVE CONSENSUS on....come on , ya big lug,NOT the things we disagree about.......the things we agree on.... you know .. CONSENSUS..like ASTM standards...
*Consensus this...Section 705.6.3 of the 1997 Edition of the Southern Building Code addresses penetrations of horizontal assemblies without a fire rating. Sealing of the penetrations must be done with an "approved material". In order to be an "approved material", the material must pass the ASTM E-136.(from the Chief, Building Inspection Division, to all residential permit applicants)So now I guess we have to start keeping the wrapper, the can, the UPC or the paperwork that comes with all the stuff that goes into a project so that the inspectors can check it off.Mike, this is just to help you get this ASTM thread started.
*....Ralph, does the Chief Inspector go on to list some approved materials?interesting little monkey wrench , hey?I was talking ASTM because they always break down into sub-committees and never publish standards until they arrive at a "consensus standard" including input from all members, industry, the scientific community,,, etc.. their standards are more "real world" acceptable.... an example would be the adoption a couple years ago of the new tear standard for roof shingles.. a great move forward in product development..
*Mike, list some materials? That would be way toooo helpful. What would the inspectors have to do if they couldn't use that government issue red pen? You do KNOW that we who get the big bucks and have our names on the projects always have enough time to keep up with all the requirements. It's just like FAA regs. The PIC is totally responsible and would be flying illegally if he did not know EVERYTHING there was to be known EVERYTIME he acted in that capacity.
*Mike, the post numbers as they show on my browser seem to be different from yours...Gene's post #36 refers to a placing a slip of EPDM on top of the footing before the foundation walls are poured in order to provide a capillary break between the footing and foundation.His post #77 refers to "alternative methods" and Lstubireks article.
*Glad the weather broke. This discussion was exhausting. I look forward to round three next winter.-Rob
*....what ? when we'll all be older and wiser....uh, huh..
*Hi Mike, et al,I just read an article in a "freebee" magazine that came in the mail yesterday...food for thought"Building felt and building paper are different products with different purposes. Both contain asphalt, but that's where the similarity ends. Building felt, which is made of recycled cardboard or rag fiber is a heavy, somewhat crude "weather barrier" used primarily in roofing. Building paper, also known as kraft building paper, is a "weather-resistive" material made to rigid standards. It has high tear strength and is used primarily to protect exterior wall sheathing. It competes against housewrap products such as Tyvek.Building felt is waterproof - just what you need for a roof. On the other hand, Grade D building paper must allow moisture vapor to pass through it while repelling water for a least 10 minutes. The breathability of building paper prevents condensation from collecting inside walls. Building felt is specified by weight (e.g. 15 pound), while building paper is specified by grade. The products are not interchangeable."FWIW, jim
*..Jim L..interesting.. the only "building paper" i've ever seen used, is red rosin paper, AKA "construction paper, and commonly used under oak floors as a slip sheet... it used to be used , at least around here up until about WWII under siding , probably as a "capillary break" that FredL sometimes refers to, although it seemed to me more like a capillary WICK...i have seen rolls of "building paper" but never used itthese terms have always been interchangeably used (which doesn't mean they were used correctly):Roofers felt, 15 pound feltslaters felt , 12 pound feltbuilders felt, roofers felt, 15 pound feltBuilding paper (which is a new one to me) class D would have a permeance of not less than 5 PERMS , listed as being a range of 22 - 43 perms,so its resistance to moisture vapor passage would be 1/22 = 0.05and 15 pound felt would have a permeance of 70 perms or a resistance of 0.014and 4 mil poly (just for comparison) would have 10 perms or a resistance of 0.1and then there is Duplex sheet, which is the laminated kraft/asphalt/aluminum foil (any metal being a "PERFECT" vapor barrier) with a perm of 0.43 or a resistance of 2.33 (r=1/perm)so .. the end of this line of reasoning is that building paper ("sheathing paper") and building felt are in the same range ..... and in last month's JLC, the tests done on Tyvek, Typar, 15 lb. felt,, and a couple others, gave the result that the only products worth considering were Tyvek & 15 lb. felt... the others let too much rain in and not enough moisture out...b unless of course i got it wrong
*Tom Silva used it under the siding on brother Richard's house. It was on the cover of TOH.Pink stuff - really caught my eye.-Rob
*Jerry. I gave an incorrect URL for the American distributor of Electrostrip. The correct URL is http://www.geanderson.com. He is in Texas (214) 428-3731
*Gentlemen. Capillarity is a suction force that draws water into porous materials, or into tiny cracks--note the tiny-- in otherwise solid materials. Capillary mean hair-like... a hair is tiny, maybe 0.004 iches.These tiny cracks may be likened to tiny tubes, capillary tubes. Any water near the tube opening will be sucked in. But with a crack say 3/8-inches wide or more capillarity will not happen. A capillary break is a substance placed between the moisture and the material to break the sucking action. One gives a concrete foundation a capillary break by dampproofing the surface with cut-back asphalt.(NOTE: Do not use cut-back aphalt because of the VOCs. Instead use an emulsion compound).Coarse gravel, as opposed to pea stone or sand, is used beneath a slab on ground to act as a capillary break The gravel's pores--the distance between the stones is too wide to allow capillarity.Note. Dampproofing the exterior of the foundation, or attaching rigid foam board insulation (RFBI) to the exterior, does not stop the foundation from sucking up water. Capillarity will suck up water in a six mile high concrete column. The mositure cannot penetrate the RFBI but it by passes the RFBI and enters the interior of the foundation through the footing. Therefore, always place a capillary break on the footing before the walls are cast.This capillary break can be polyethylene or an elastomeric compound.Capillarity happens on clapboard siding. The tiny opening between laps allows rain water deposited on the clapbaod face to be sucked up--against the force of gravity-- between the laps and deposited on the back of the siding. I hope this non-rigid scientific explanation of capillarity helps. GeneL.
*Gene... i thot it was very succinct.. a better explanation of capillarity i hav nevr red..now , as to practicalities...i can see it would be relatively simple to put a cap.break on top of a footing prior to them forming the wall.. and apparently, pretty effective..about half of the time, here in RI, 12" walls are poured with no footings.. usually , the companies with older form systems... the only ones pouring footings (and 10" walls ) are the guys with the Symmons style forms, they can only be set up on footings...?do u think a piece of poly under the bottom of a 12 " wall will be an effective cap.break?...
*Mike. It will work as long as it is not punctured. Why a 12-inch thick wall,Mike? Supporting brick? Eeven a 10-inch wall is overkill. Canadian researchers have done a lot of research on the suitability of 6-inch walls. Building codes allow a 6 inch wall depending on the height of the unsupported backfill See Table 401.1.1a in the 1995 CABO One and Two Family Dwelling Code. I'll look in my library and see if I can locate copy of Canadian research paper.GeneL.
*Rhode Island code for 1 & 2 family dwellings;as normally interpreted by Bldg. Inspectors;12" wall , no footing10" wall with footing.. i know what you mean , but that's the way it is...and that's the form equip. everyone has....the table you're referring to in my copy of that CABO(1995) whch is the version we use here with RI amendments (blue pages) is table 404.1.1a, seismic zone 2, unbalanced fill 6' would allow 6" wall, but try to get it poured, unbalanced fill of 7' wud req. 8" wall...anything other than that & yur probably into ICF's.....i think they want something they don't have to worry about and don't need a P.E. to supervise the pours, yada, yada, yada.....right now there must be 40 form companies i cud call, but none of them want to do a 6" pour...another item is i have Andersen steel bucks for 10" walls & 12" walls and that's what i use for any basement windows...u know how it is....
*Mike. Steel window bucks are a NO-No in an energy efficient house.So the foundation people in RI have a captive audience...take it or lump it. GeneL.,
*no, no, no, Gene... the Andersen Steel window bucks are a temporary buck that comes out when the forms are stripped... the window itself is either an Andersen basement window... or one of the vinyl knock -offs that are the same size as Andersen so they also fit into the temporary steel bucks...the reason i own them is because none (or almost none ) of the form companies use anything other than the steel windows ..the ones that you and i, and any energy concious builder, won't use...