Tight houses, are we on the right track?
I think in my 30 years in the trades I’ve seen a steadfast attempt to seal buildings tighter and tighter in the name of reducing heating and cooling costs.
And while building scientists may have achieved a level of success stopping air movement through the envelope, we are faced with more and more health issues which led to the widespread use of mechanical air handlers to insure the flow of fresh air into, and less healthy air out of the building.
It seems like we are relying on these mechanical devices more and more. It’s not hard for me to imagine a “climate control computer” which will measure relative humidity and start and stop the necessary air handling equipment to reach a specified range similar to the way a thermostat controls the temperature…someone out there is probably reading this thinking “no fooling, Jim, we’ve had those for years”.
But something doesn’t feel right about all these “advances”. It seems like we made errors in judgement a couple generations ago and ever since we keep piling more and more fixes on top of one mistake after another, that we are spiraling farther and farther in one direction instead of stopping and reevaluating certain ideas about the buildings we live and work in.
Am I alone in this uneasy feeling? You know, like when you open up a wall in a hundred year old house and the lumber looks better than anything you can buy today? That compared with taking apart a fairly new building and finding mold?
Somebody help me out here. What the heck am I missing?
Replies
"Am I alone in this uneasy feeling?"
Nope! I feel the same.
Lotsa info out there about the new "sick house syndrome" ...
we get to have radon tests and "Remediation Systems" here ...
basically ... the old gases that used to flow right thru the old drafty walls is now being held tightly inside the conditioned space ...
Unless you pay some guy to put holes and pipes thru your slab and power vent it out thru the roof.
House I grew up in and the house I own now ... both have old drafty walls ...
and no radon to speak of.
I presonally think we over build too much ... and are definitely are building too tight.
Environmental allergies are going thru the roof ... we're raising a whole new generation of sick kids ... all thru "better building" ...
Jeff
Buck Construction
Artistry In Carpentry
Pittsburgh Pa
In the house I grew up in, the furnace would kick on while I was sleeping and drive dry air up my nose. I'd often wake up with a sore throat. Now my sinuses are shot.A tighter house has less furnace cycling, and higher humidity which helps prevent the dry sinuses. The higher humidity won't cause any mold/condensation problems as long as there are no cold spots on the walls or in nooks and crannys. On the other hand, indoor humidity would cause problems in the leaky house when it leaks into the wall system or attic and condenses. In the tight house, it doesn't leak to any cold spots by definition.To check for pollutants, talk to Dave Lennox
http://lennox.com/healthyadvantage/The tightness of my current house is saving me about $80/month in winter. That savings easily pays for the proper mechanical ventilation system.Here is a problem I'll give you. Subsequent owners of my house might ignore the ventilation system, let it fail, or even take it out. Homeowner education is the only solution. For that I propose a new periodical called Fine HomebuyingEdited 6/2/2005 10:36 pm ET by KevinD
Edited 6/2/2005 10:37 pm ET by KevinD
I dunno.
I still agree with Jim.
sounds like were starting to build robots instead of homes.
Then again ... I do remodeling. I try to match existing while still meeting code. I can't build the ultimate/extreme tight addition and attach it to an 80 year old house.
Jeff Buck Construction
Artistry In Carpentry
Pittsburgh Pa
we get to have radon tests and "Remediation Systems" here ...
basically ... the old gases that used to flow right thru the old drafty walls is now being held tightly inside the conditioned space ...
Unless you pay some guy to put holes and pipes thru your slab and power vent it out thru the roof.
Jeff, my sister's family live in an early 1900's house. The basement sticks up a bit higher that typical for that age of house (drafty old windows are about chest high and about twice the size of the typical rectangular basement window).
I thought for sure there was no way they'd have radon in that drafty-#### basement. But the results came back that it was VERY high. So a drafty house is no guarantee that you don't have radon.
Environmental allergies are going thru the roof ... we're raising a whole new generation of sick kids ... all thru "better building" ...
That has to do with the materials being used to build the structure and the resulting off gassing. A 100yo house has probably out gassed about all its going to (although you still have the lead paint issue).<!----><!---->
jt8
It's better to light a candle than to curse the darkness. --Chinese proverb
Edited 6/3/2005 10:02 am ET by JohnT8
In my climate, the outside air is more polluted with mold, smoke, dust, and humidity than my inside air for months on end. That is because my house is built air tight and is mechanically vented across a 4" 95% pleated filter. I maintain relative humidity with a dehumidifier at less than 50% RH year round. I air condition my 4200 square feet for around a dollar a day in the Texas summer. I left my home today with the AC off and came home 12 hours later to a 2 degree rise in temperature. High temperature today was 91 degrees. I suffer alergies only when I go outside, never inside.
When the energy crises happened in the early and late seventies, there was a push to seal and insulate homes to conserve energy without the knowledge to do it safely. Today, building scientists are finally figuring out how to create tight, safe, energy efficient buildings. We have learned from the mistakes of the past and continue the development of building systems that are differentiated for climate and use.
Until you control the building envelope, you can't control the air. I have done a lot of remodeling in my day and there is nothing great about an old drafty house. Dust mites and mold spores are commonly percieved as that old house smell. Interior RH is too low in winter allowing viruses to flourish and spring and fall RH is too high allowing mold and bacteria a foothold.
Healthy houses need to have controlled interior air or else need to forego AC and remain open air cabanas. Tossing insulation and AC into an old leaky houses from the 50s has led to some very unhealthy living conditions. There have been some huge mistakes in this industry. Recently I learned of a house that was torn down that I worked on in the mid 80s. The inspector allowed us to prime the exterior sheathing with paint instead of wrapping with felt paper. We then covered this with wood siding. Inside, we followed the insulator's recommendation of putting poly inside the walls behind the sheetrock. This is in a hot humid climate. The house filled up with mold and was destroyed after 15 years.
Ignorance, not air tightness, is the enemy of a healthy house. Thank you for the opportunity to share my opposing view.
Ray, let me add another vote in support of your point of view.I agree that a lot of what goes on in the industry is slow evolutionary learning instead of science-based research. Approaches that seemed to make sense 10 years ago turn out to be false because they didn't take the local climate, construction techniques, etc. into account. Unfortunately along the way, tight houses became synonymous with sick building syndrome.However, rising energy costs will continue to put the whole issue of super-insulated homes in the proper perspective. Quite simply, more and more consumers will demand homes where uncontrolled infiltration is very low, where annual heat losses and gains are minimized, where operating costs are low. Those kinds of customers may be rare now, but their ranks will likely fill as awareness and energy-cost pressures start to take hold. Once consumers (and lawyers) catch on how leaky homes with AC systems can actually start growing mold more efficiently than properly-constructed homes, a couple of builders are going to have very painful life experiences. I say, learn about this animal, because one day consumers (or their advocates) will know what ACH, BTU/(sq ft x DD), etc. mean. Once real metrics (not, sometimes arbitrary, codes) get applied to the building industry, everyone will have a much harder time passing inspection.As Ray points out, there are many different ways to build houses, some not suitable for whatever climate the house is in. The vapor-barrier location debate is just one example of how the quest to achieve healthy insulation with substandard materials (i.e. fiberglass) can get a lot of people into deep trouble. Now add in the effects of people demanding AC inside their homes and you have the recipe for mold, etc. Yet is the "tight" home at fault? No, it is the misapplication of materials that got the builder/HO into trouble in the first place.I like Rays approach of using insulation as a sheathing barrier outside the home as a means of bypassing the issue of where the dewpoint is going to be. The PERSIST model of building walls certainly seems to have a lot of merit and appears to be largely climate-agnostic (with some outliers at either end of the spectrum needing a closer look, naturally). Another approach is to build deep walls and foam them shut, though you still have to worry a bit about the studs.Ray's experience is the proof in the pudding. It's quite remarkable to cool a house in TX to the tune of $1 a day. Yet many builders do not want to go to the lengths he did building his own home because it increases the $/sq ft cost, the clients want more bling, not a better house, etc. IMO, it's better to be prepared for a customer like myself who demands a tight, well-insulated home as part of your 'these are the homes I can build for you' palette.
I'm just a homeowner and hesitant to stick my oar in here, but I've been thinking about this subject a lot lately, especially since Ray's other thread, and I want to throw in a few things that haven't been mentioned - so go ahead have at me. Just remember that I have a newborn who doesn't sleep well, so if I respond hormonally, it's because I AM.
1) Research has shown that exposure to natural allergens and fresh air results in healthier babies and stronger immune systems. Why they needed research to discover that fresh air is good for you I'll never know. But the first part about the allergens is this: like most other body parts our immune systems require exercise. Getting 3 or 4 normal colds (or in the case of young children 7 or 8) a year is NORMAL, it can help stave off getting really sick because your immune system gets the workout it needs. People who live in climate controlled, ultra clean, hospital filtration homes get sicker because their immune systems can't respond as effectively as us slobs who have pets. Likewise, people who have allergies but avoid them completely, can have a significantly worse response when they are faced with it, depending on the allergen. Hence, allergy shots, which help reduce allergy symptoms, are really just injecting the offending allergen into one's system to tolerize the system. My point in this lengthy treatise is that perhaps a tight, well-built, well-filtered system is a healthy house, but that doesn't necessarily mean it is contributing to the overall good health of the occupants - it could in fact be doing silent damage.
2) I am confused because all of this talk about controlling air movement seems to really be talk about controlling moisture. I live in a mixed climate where the VB is generally recommended on the inside of the studs. But this always seems sorta silly to me because with electrical outlets, fixtures, hanging pictures, etc. there are always holes - once the house is built the homeowners are not going to foam around new holes in the wall. And really, having the moisture held against the drywall doesn't seem so great to me. I read Ray's thread with interest, but my dim little mind doesn't comprehend where holding the moisture against the sheathing is any better. He argued that there was no condensing surface, but the vapor has to stop somewhere, so I'm not convinced that the system he presented is superior to moisture permeable barriers, but I assume that is my lack of knowlege and experience.
3) The idea of requiring mechanical means to get decent air in the house goes against my passive soul. Just as we site a home to take advantage of sun in winter and prevailing breezes in summer, it seems that requiring an air handler to get air is a little scary. Does this building envelope fail if somebody opens the window? What about folks who want a house that is less dependent on technology? Is there a passive way to provide fresh air into the home? If you are going to go mechanical, why not go whole hog with a device that sucks the air out of the rooms(so it never makes it into the walls), dehumidifies it , filters out every potential poison or allergen, and then returns it with a nice, fresh, mountain breeze scent, courtesy of Glade? While we're at it, just paint a nice picture where the window would be, it's a much cheaper way to build a house, and you don't really need to be able to open the windows anymore anyway with the new, improved, scientific building envelope.
OK, ignore my facetiousness in the last couple of sentences, but that is the sort of thing that pops in my mind every time this subject comes up.
The reality is a lot less anal/obsessive than suggested. My house, for example, doesn't require mechanical means to get fresh air. We have a house that usually has nothing mechanical running, and we open doors whenever we want without using airlocks or scuba gear. The house passively draws air in through a vent that routes through the dehumidifier's filters. That's all. Cleans up pollen, woods dirt, mold. Very low maintenance, very passive, very fresh air. My dd's 7 yo friend visited and said, "It always smells so good here, not like mom's house." Wish I knew how to get across that a properly climate-controlled building is just comfortable, not like living in a hyperbaric chamber...it just feels fresh and comfortable, not sterile or anti-bacterial or Glade-y...just fresh and comfortable.
"My point in this lengthy treatise is that perhaps a tight, well-built, well-filtered system is a healthy house, but that doesn't necessarily mean it is contributing to the overall good health of the occupants - it could in fact be doing silent damage"But that does not prohibiting you from throwing them out the house and locking the door behind them at 8 am, throwing a sandwich out the window at noon (and it hits the dirt a little better), and not letting them back in until 6 pm following a hose off at the back door.VS, going in an AC'd car to an indoor batting cage and only allowed outside for 2 hours that it takes to play a game."I read Ray's thread with interest, but my dim little mind doesn't comprehend where holding the moisture against the sheathing is any better. He argued that there was no condensing surface, but the vapor has to stop somewhere, so I'm not convinced that the system he presented is superior to moisture permeable barriers, but I assume that is my lack of knowlege and experience."Take a cold beer and set it out and you will start to get condensation on it. (substitue soft drink in Utah). The cold can is the cold outside. the warm moist air is the relatively warm moist air on the inside. You don't have any kind of barrier between the cold outside condensing surface, beer can, and the inside air (warm/moist air).Then do the same thing, but put the beer into a beer cozy. The insulation provides an thermo barrier so that surface warm enough so that the air stays above the condensing tempature. The material that is used for the insulation also forms a barrier so that moisture can't move through it to the cold can.Now, in THEORY the barrier that Ray uses does not need to be used. The proper insulation can also be a barrier for the movement of water. But it also provides a barrier against water. Now that could also possibly be handled by the right type of insulation. BUT IT WOULD REQUIRE EXTENSIVE DETIALING AND MINOR LEAKS COULD BECOME TRAPPED BETWEEN THE INSULATION AND THE SHEATHING." Does this building envelope fail if somebody opens the window? "Well it depends. Ray said that in his climate the OS air is worse than the inside. So you want to control the amount of it.In my area (Kansas City) I have the windows open about 4-5 months out of the year. But that does not mean that I don't want to control the air leakage into the house the other times.
I agree that Ray's techniques are indeed valid.
It's all about controlling the condensing surface...where does the thermal gradient hit the dew point? Hopefully somewhere buried in the thickness of the polyiso where there is no viable moisture.
Ray puts his polyiso on the exterior. He's down south.
I put mine on the interior. I'm up north. I'm more at a supposed risk, though, since I have all sorts of penetrations in my polyiso...in the exterior walls it's mostly electrical boxes. Still, it's in the details. I just have more to contend with. His empty stud bay wall takes all that out of the equation, though, simply using the framing as nothing more than very large furring strips.
I don't think stick-framed is neccessarily the problem. Stone houses can be cold, damp, etc. I've stayed in plenty a stone space where the chill never seemed to get shaken off.
Well-constructed stick or well-constructed stone. Either works well. If done well.
If I ever build another house for my family, though, I'll certainly give Cloud a call to pick his brain.
Mongo,
there is a dramatic differance between a stone house and an ICF house.
Just to be clear an ICF house is a home where they pour concrete into foam "blocks" that are put together like leggo's toys.. (don't worry there is plenty of rebar and other such reinforcements in the"blocks" before the concrete is poured..)
(not trying to insult you if you are already aware of what an ICF house is, just it's not as common as stick built)..
However there is no vapor barrier in a stone house and with the moisture that is normally wicked up from the ground thru concrete I can understand your statement about how cold/damp a stone house feels..
My home has the basement walls made of ICF;s and you can't believe how warm and dry it feels in the basement.. I've been in a few ICF homes around here and they are just as warm and dry, thus it's a common trait of ICF's
Now to further compound the issue I have stone on the outside of my home. I could use stone if the whole house were ICF's. Heck if you wanted to you could put stone on the inside and outside of ICF's and have a bullet proof house..
Exactly right. Stone and ICF are two different animals. SIPs are different too.
All have inherent plusses an minuses.
I have read all entries with great interest as my first new home will be built in a few months. I have read and read and have come up with the following for construction:exterior-Hardi-Plank Siding, then Weather Trek with Valeron EVD Technology housewrap(which has a unique 3 dimensional engineered surface that provides drainage for any water or moisture that happens to get past the exterior siding, then Styrofoam extruded polystyrene insulation, next 2 X 6 framing, next 5 1/2" fiberglass insulation, followed with wall board. Am I doing this correctly? Will I have condensation problems?
What is your location? Climate?
West Virginia which has a mixed climate.
I disagree with Mongo, which rarely happens, it seems. You have a good bit of winter there. I checked for West Virginia and found an average temperature of 32 degrees for the month of January. If the foam board has an R-value of 5 and the FG has an R-value of 19, and if the interior temperature is maintained at 70 degrees in winter, then we can do a math problem on this wall.
The deltaT of this wall is 38 degrees in January. The temperature of the inside surface of the foam board would average at 39.9 degrees. This is the first condensing surface. In order for this wall to be theoritically safe without freely passing moisture to the exterior through diffusion, you would need to maintain a certain RH inside the building. That RH calculates to 33%. In other words, if your wall is built with a foil faced foam(impermeable) you would need to maintain the RH inside this home at less than 33% RH to avoid condensation on the inner surface of this sheathing. Even with more permeable sheathing, you would be very close to the edge. You could change the surface temperature of the sheathing by using more foam or less FG or both.
I would not build this wall in your climate. My wording may be difficult to follow. If you need a better explanation, I will be happy to provide it.
I took his word that it was a "mixed climate", but you're correct that foam only having an r-value of 5 would likely be insufficient.
I didn't go back and read my original post, but I thought I mentioned 2" of polyiso that would give something along the lines of R-12 to R-14, depending on what numbers you use. Polyiso got confusing after they changed the blowing agent used in its manufacture. I liked the old easy to remember R-7 per inch.<g>
Again, more than R-5 of foam would be required or you could get what Ray mentioned. A possible condensing surface. Two inches would be great.
'Course, I'm the stump in the ground that believes that polyiso only exists in 2' thick sheets. Anything less is tissue paper!
Building Science map shows that about 1/3 of WV is Mixed Humid and 2/3 cold.And I have noticed that Kansas City (where I am) is clearning in the Mixed Humid region. On the old maps it was in the cold region.http://buildingscience.com/housesthatwork/hygro-thermal.htm
>And I have noticed that Kansas City (where I am) is clearning in the Mixed Humid region. On the old maps it was in the cold region.Do you need any more evidence of global warming? R R R
Thanks for that link, Bill. I see I'm in the newly defined "Marine" climate, but until they do more research I should use the "mixed-humid" ideas. That seems about right to me.
Crimmony. My head is spinning with this stuff.
Okay, one of the things that seems to come up in these discussions is controlling the moisture/air movement from the unconditioned crawl space into the walls, and through the floor.
Has there been any discussion about why we continue to use continuous perimeter foundations? Couldn't the foundation be a series of piers and (above) grade beams, with an airtight membrane across the bottom of the joist/slab plane similar to the membrane on the exterior surface of Ray's walls?
Then air, water, radon, or whatever, would move freely BENEATH the floor plane instead of up through the structure? Why do we work so hard to seal the top and sides of houses and continue to use a foundation detail that traps the very things we are trying to keep out of the envelope?
Yes, you could do that. You would, of course, need to control the temperature of the first condensing surface through proper placement of the insulation (probably to the exterior of the membrane).
The issue then becomes one of aesthetics. It is rare to find the floating house to be an acceptable look. You also give up the ability to do masonry veneers. How would you address these issues?
"The issue then becomes one of aesthetics. It is rare to find the floating house to be an acceptable look. You also give up the ability to do masonry veneers. How would you address these issues?"
Well, I was thinking about that, Ray. And I think a large part of why you (and I) immediately think it wouldn't look okay is because it's not something we often see. But to get back to a conventional look I'm thinking the house might not have to be much higher off the ground than what we're used to seeing everyday. How much actual clearance would you need between the bottom plane of the floor and top of grade...a few inches? Maybe a foot? 18" so a person could slide under there to inspect on occasion?
I'm thinking something better looking, but similar to lattice, or mobile home skirting...even something as pleasing to the eye as properly selected shrubbery.
Of course, after a while, we might start to actually use that space under the house to park vehicles, or as a dry recreational area, say on a sloped lot where we might see a daylight basement now? In time, I think perception could change regarding asthetics as the usefullness of this design concept becomes more obvious.
I think asthetics could be handled without too much trouble.
Edited 6/4/2005 5:42 pm ET by jim blodgett
In the mid west I think of that space as a varmit hotel . The ground hogs would have the dirt tunneled in a matter of weeks and then it would be piled up right under pushed up to the underside . then you have the skunks that come acalling . All of them nice tunnels to stink up. Can you imagine trying to winch out aunt Tilly after she gets stuck trying to retreive little Johnnys ball. I think that is why we use basements here aunt Tilly don't get stuck and the beer keg stays cooler.
hehehehehe
The bumpouts on my house that are exposed to free air underneath are foamed. About 6" or so.
In my basement, the ceiling has a simple sheet of 6-mil poly as an air/vapor barrier. No heat in the basement, but it stays about 62-65 degrees year-round. No moisture problems, etc.
A buddy in TX did his house on steel piers/beams. The bottoms of the TJIs are skinned with foil-faced polyiso, then hardware cloth over the RFBI to varmint-proof it.
Well, I'm a little confused. Are you suggesting because of my climate that my Styrofoam rather than being 3/4" be increased to 2"? Why did my architect stipulate 3/4", do they not study these things? Regardless, I want to do what is right according to the science of it all. So please address this issue again and tell me what I should do.
Thanks--this is too important to screw up!!!!
The thickness of exterior foam is not a one size fits all number. I'm up north in a cold climate. Your needs in your climate will obviously vary. If Ray's numbers are correct for the wall detail you indicated and for the delta-t's that he calculated, then yes, you need more foam. For that type of wall structure.
Tell you what, the other guys here have referenced a climate map and say that you're either in a mixed/cold or a cold climate instead of a mixed as you originally indicated. Take a look at it yourself and see what climate is indicated for your actual location.
A mixed climate can use a cold wall. So can a mixed/cold as well as, obviously, a cold.
It's probably be easier to simply build a cold wall instead of a mixed, since you seem to be in a cold/mixed or col environment.
Do architects know it all? No, no one really does. Some are educated on making things purdy, some have additional knowledge on how to make purdy things work correctly in the real world. Your architect may be the former or the latter. However, if (s)he's a good one, he and your builder will know your climate better than any of us on this forum, and will know how to build to suit that climate.
Your concerns are valid. Conflicting info can be disconcerting. Moreso as the timeline for construction approaches.
You might want to meander over to the building science website and take a look around yourself. A lot of the guys on this thread have been referencing that.
Might be something as obvious as http://www.buildingscience.com or something similar. Try googling if the link I wrote is bad.
Look at the mixed as well as cold climate houses.
Best, Mongo
So, according to what I understand that you suggest, I should increase my foam and decrease my fiberglass insulation, is that correct? Or can I stay with the 3/4" foam and just decrease my fiberglass insulation?
This is all "rocket science" to me.
I will be using Weather Trek as a house wrap under Hardi Plank Siding. Is this ok?
An interesting read.
http://healthandenergy.com/dehumidification.htm
Interesting read, indeed!That text hit on all the important aspects of keeping a basement healthy: Keep the water out, keep the vapor out, allow air circulation to prevent mold growth. I would add one more item to the equation: right-size an AC system, if you have one.A properly-sized AC system will remove the proper amount of latent heat to allow you to hit whatever RH you desire. In our home, the latent heat is almost neglible due to the insulation package. Thus, I chose air handlers with 1-ton more capacity than the condensers attached to them... maximizing the sensible heat removal. In areas where the latent heat proportion is much larger than the sensible/latent ratio of 70% that most equipment designers strive for with their matched coils/condensers, it would make sense to oversize the condenser... This is one aspect of AC systems that is frequently overlooked... it's not just about matching the total tonnage of the cooling equipment to the total load, but to match the sensible/latent heat removal needs to the actual equipment capacities.
One reason for the reduction in electrical demand exhibited by their dehumidifier is that the first year is always higher until the moisture content of the contents of the space is reduced.
The dehumidifier that they used was a very inefficient model. The model that we use is rated at 5.5 pints removed per KWh. That is about 1.5 KWh per gallon removed. Around here that's around 13 cents per gallon.
Of course, dehumidification makes no sense in a house that is not very tight; because, you will just be drying outside air continuously.
All in all, the author struck me as being somewhat knowledgeable.
Sam,Referring back to your original post, you described your proposed wall as:"exterior-Hardi-Plank Siding, then Weather Trek with Valeron EVD Technology housewrap(which has a unique 3 dimensional engineered surface that provides drainage for any water or moisture that happens to get past the exterior siding, then Styrofoam extruded polystyrene insulation, next 2 X 6 framing, next 5 1/2" fiberglass insulation, followed with wall board."Maybe I'm misunderstanding something. But you have no exterior sheathing. Is there sheathing at the corners? And if so, then you definitely have an interior condensing surface on that sheathing.If no sheathing, what's preventing racking?Rich BeckmanAnother day, another tool.
Thanks for your input. All corner walls will be substantially metal braced. The windows, dormers and doors will have double headers.
You mentioned being in a mixed climate, while this is not my forte, I'll offer a bit of info.
Essentially, yes, what you have described will work. You're using a method that, theoretically, has the vapor retarder somewhere towards the in the middle of the wall. "Middle" meaning the approximate "thermal middle" in regards to R-value.
In a mixed climate you want to control moisture being driven into the wall assembly, but also once the moisture is there, you need to allow it to dry. The kicker is that in a mixed climate you need to allow it to dry to both the interior and the exterior, depending on the conditioning season that you are in.
During the cooling (summer) season moisture, Mother Nature will try to drive vapor from the hot outside the cool, air-conditioned inside of your house. From exterior to interior. To the wall, your theoretical vapor barrier will be the exterior face of the rigid foam board insulation (RFBI). With a whole-house system you can also maintain the interior of the house at a slight positive pressure. That will further reduce the delta across the wall assembly. Your air conditioning will naturally dehumidify the interior during this season.
During the heating season, the gradient will be reversed. Now moisture will be driven from interior to exterior. Now, the inside face of the RFBI, the face that is against the framing, is the vapor retarder. You want to control interior levels with moisture control at the source, as well as limiting interior moisture levels through controlled ventilation.
With the assembly tou describe, for the wall cavities FG or dense-pack (so it won't settle) cellulose can work. Cells have some advantages over FG in terms of air infiltratiom sound deadening, and holding and dissipating moisture.
You wrote about using a house wrap. The Weathertrek has a dimpled surface to promote drainage, because it's dimpled (vs having drainage channels like some other products) it's a uni-directional product. There is no requirement to orient it in a specific manner. That can make installation easier.
Still, it can be considered redundant. If you tape the seams on the RFBI, the face of the RFBI will act as a drainage plane, and the RFBI itself is an air barrier.
Carefully choose the type of RFBI you use. The better choice would be one that has more resistance to moisture passing through. A foil-faced product provides the most resistance, 2" thick polyisocyanate would give you aproximately R-13 on one side of your barrier and with FG, R-19 on the interior side with an excellent perm rating due to the foil.
Unfaced styrofoam less than 1" thick would give you a less balanced wall (in relation to the R-value inside and the R-value onn the outside of the vapor retarder), and unfaced polystyrene also has a much higher perm rating (higher perm rating means vapor can more easily pass through) than does a thicker faced product. Meaning, thinner unfaced polystyrene would allow moisture to be more easily driven through your wall assembly than would a foil-faced product.
Hope all this makes sense. Got to run my 9th-grade daughter out to school, she's taking the biology SAT this morning.
Again, mixed climate is mixed climate. There are indeed a few ways to skin this proverbial cat.
Sam,
Where do you live? have you considered SIP's or ICF's?
Thank you Bill. I have been interested to hear your input on these subjects and I'm not disappointed. I typed for a long time here but I suppose there are several things that I didn't cover. I may have made assumptions about the backgrounds of the audience. It took me a while to understand all the issues back when i first got pulled to the dark side.
The idea that we need to constantly live in a polluted environment in order to be immune to it flies in the face of medical opinion. Allergy shots do in fact build up your immunity to the allergen but they do it without damaging your lungs and sinus tissues. Allergy doctors long ago figured out that they had to find ways to build the tolerance without exposing the patient's lungs to more damage. The more exposure the sinuses and lungs have to the allergen the less able they become to tolerate the allergen. The American Lung Association has guidelines for building healthy homes that include air tightening and mechanical ventilation.
In Austin TX., we have an annual cedar pollen season. Most people do not react to it until they have livced here for several years. After the cedar pollen has attacked their sinuses for several years, they come down with their first case of "cedar fever". They never think that is what it is because they have never had it before. They will have it every year from then on as long as they live here, unless treated with anti-histamines and nasal steroids. Those that refuse treatment can expect to progress on to sinus infections, perhaps bronchitis, possibly even pneumonia, depending on the health of their lungs.
We have good air here sometimes. The prevailing south breezes bring gulf moisture, smoke from Mexican agricultural burns in spring, and high levels of air pollution from Houston refineries and Mexico City. We get to enjoy cedar pollen, oak pollen and ragweed seasons that turn our cars orange, green, and yellow in that order. last but not least, we are blessed with some of the highest mold counts in the country a large part of the year. One last joy that we get to experience is the regular burning of juniper trees by land clearing home owners. They tend to do this after frontal passage brings welcome rain. The good air happens when northern cold fronts bring fresh air from the Rockies and Canada. When that happens, we open the roof hatch and a few windows and flush out the house, unless a neighbor happens to be burning juniper. Kinda make ya wonder who would want to live here but I'm not exagerating in the least.
In regards to the statement, "vapor has to stop somewhere", vapor drive only happens if there is a force to drive it. This can be pressure differential, temperature differential, or a differential in moisture content. Moisture moves from hot to cold and from wet to dry. If the plywood sheathing and sheetrock are kept at the same temperature and moisture content as the interior air they will reach equilibrium. Water molecules will constantly attach and detach from their surfaces. The approximate number of water molecules on the surface will remain about the same.
I'm going to explain how this works. (God help me) Water molecules are very small. A billion of them end to end are about a foot long. Water molecules are in constant movement, flying around and sticking on things and flying back off again. As water molecules cool, they slow down. The slower they are, the less likely they are to fly back off of a surface. The warmer air becomes, the more water molecules it can keep bouncing around. The colder a surface becomes the more "tired" the molecules become. The molecules will stay attached to a cold surface longer and will start to collect. The warmer and moister the air is and the colder the surface is, the faster the moisture will collect on the surface. This happens long before surface moisture appears, slowly raising the moisture content of the surface. Eventually, if the surface temperature is cooled below the air's ability to hold it in motion,(dew point) water will condense on the surface. This is why we try to control the temperature of the surfaces that we are trying to protect. As it turns out, this is easier to do than controlling the movement of moisture though air transport of diffusion(movement of molecules through a solid material).
Polyethylene vapor barriers are an attempt at controlling moisture movement but they can cause problems during the season that their placement was not designed for. Summer up north or winter down south can caus vapor drives in the opposite direction of that which we design for.
Aimless- thanks for the opportunity to respond to these questions that I'm sure are shared by many. The water molecule is a fascinating subject and understanding it's behaviors is central to understanding building science. It is a short college course in itself and once it is understood, the lightbulb goes on about so many of the things that we experience in nature and in our homes. I know that I have only briefly touched on it but I hope it has helped.
Thanks again Bill and others for helping in the process.
"The idea that we need to constantly live in a polluted environment in order to be immune to it flies in the face of medical opinion."There is a difference between an "overload polluted enviroment" and what Aimless was talking about.Small require dozes of "ordinary 'pollution'". That is not really an area that interest me so I have not done any studying on it. And just look at the headlines when I see some mention.But I believe that there have been some studies that show that children exposed to "normal" amounts of dirt and germs have less problems with allegies and asthma than those raised in more steril enviroments.
Ray,
Thanks for the in depth explanation. Just a note though, I wasn't talking about living in a polluted environment, I was talking about living in a normal environment - not too clean, not too dirty. I come from a family of asthma and allergies, so this is a topic of great interest to me, and recent research shows that TOO clean is not so good either. As in all things, moderation is key and there is a happy medium.
my little boy was born with eczema. At the time .. for a little baby ... the rash was quite severe. All sorts of doctors ... all sorts of tests ...
allergies was the decided upon cause.
Our allergy doc and the hospital specialist pretty much said what U stated.
odds were ... he'd outgrow it ... or more likely ... adapt.
grow up in "too clean" an environment ... and the real world dirt will kill ya.
my personal analogy .... U remember the "dirty kid" back in grade school ...
always covered in dirt and boogers?
he was a pig ... but he never really had to miss school because he was sick, huh!
Jeff Buck Construction
Artistry In Carpentry
Pittsburgh Pa
Jeff,
While I did have pretty good attendence, I did in fact happen to miss a couple of days of school.
Never did catch what the other kids had cause no one would get too close to me.
I don't live in a clean room. I just don't wake up with a stuffy nose anymore.
I couldn't agree with you more. It began with office buildings and schools being built with windows that would not open. Then the R-2000 program where houses were subject to a pressure test to prove how tight they were. Inhabitants were fed hot, cold or fresh air through a tube. Nobody complained about that, we only hear about energy savings, energy savings.
Can some of the blame can be put on Industry Research? Pro product testing and heavy lobbying have substantialy changed building codes over the years. What better way to ensure profitability than forcing people to use your product?
I think it is not the 'tightness', but rather the leaks that cause the problems.
An old house with no insulation can have leaks into the building cavities, and nothing really bad happens. The moisture just finds its way out the next time the weather changes. Now you add some insulation, and the moisture still collects in the cavities, but it does not dry out. Technically it's 'sealed' a bit more now, in the sense that less air is escaping the structure, but the overall situation is worse.
If you want to have insulation that works, you need to control air movement.
But codes are not fixated on air movement. They require silly and arbitrary things like vapor barriers, minimum R values, and venting. Fiberglass insulation remains the most popular product by far. So buildings are built to code, and they still get sick. Better air sealing and air control techniques are the solution, not the problem.
Certainly there are tradeoffs. One is radon. Realistically though, we cannot afford to build structures drafty enough to vent off radon. Energy is just too expensive.
They can build houses in northern manitoba that only cost $50 per year to heat... Superinsulated. No furnace required. If I ever build a new house that is what I am going to go for. The regular usage of the home is enough to heat it.That is how to reduce greenhouse gasses.I love my old house and don't plan to give it up. When we sealed it up last fall I disovered that leaks control moisture. Since then I have learned a great deal about the subject. I agree with Dr. Joseph Lstiburek on this one "completely seal the building envelope and then use controlled mechanical ventilation". That lets you have any environment you need for comfort (given sufficient insulation) and keeps moisture from building up.If my house wasn't a 100 years old... there would go a really fine hobby.
What exactly did you do to seal up your home. My 100+ year old in Pensacola has 13 ft ceilings and multiple (over 40) 8 ft windows. Would be interested in how you would approach that.
>>Somebody help me out here. What the heck am I missing?
Extremes.
I grew up in the Chicago area and the insulating and venting issue was much bigger there than here (Fredericksburg, VA). Right now I have windows open and our HVAC system has been dormant for at least 4 weeks. Not so in IL (or better yet, Duluth, Bangor, or Tempe).
I think that an educated builder can now produce a house that is much more energy efficient than homes of yesteryear and could save thousands a year in conditioning costs.
We get into trouble when the guy who doesn't know anything about building science builds a tight home with no ventilation or uses three vapor barriers in his exterior walls.
Jon Blakemore
RappahannockINC.com
"It's not hard for me to imagine a "climate control computer"...."
Sounds like a plan to me. I wouldn't be surprised to see those in houses in the next 10 years.
I'm not sure I buy into all the "sick house syndrome" stuff. There certainly are houses with problems. But that doesn't mean EVERY house that's tight has problems.
I think the way we're building houses (in general) is far better than they were ever done in the past. And things will continue to improve.
What Ray is saying seems like a great approach. Plus, he writes so well it's easy to follow his logic. Seems like this system could have potential, for sure.
All I'm saying is, every few years I read about some system or another that seems like "the" answer until unforeseen problems pop up. Then we deal with that set of problems. It all seems reactionary to me.
This all makes me wonder if the problem isn't farther back in our evolution of building practices. Maybe the idea of a wood framed house in certain climates is flawed to begin with. Is that possible?
All I'm saying is, every few years I read about some system or another that seems like "the" answer until unforeseen problems pop up. Then we deal with that set of problems. It all seems reactionary to me.
I agree. I don't know what the solution is though. Building practices seem to be more of a slow evolution rather than a revolution. Although many of the new systems claim to be revolutions (makes good marketting).
jt8
It's better to light a candle than to curse the darkness. --Chinese proverb
Maybe the idea of a wood framed house in certain climates is flawed to begin with. Is that possible?
heh heh I knew that was where you were going in the first post.
>Maybe the idea of a wood framed house in certain climates is flawed to begin with. Is that possible?Ooooooooooh, do I get a vote? <G>I'll side with Ray on this one. I don't have a choice. My buildings are essentially air tight just by the very fact of their construction. By definition we'll only have air where we intentionally place an opening--door, window, vent, chimney. Elsewhere it's continuous and pretty well impervious to air and even moisture infiltration.So we don't have the options that traditional builders have to create a tight or not tight house. We have it and have to work from that premise.My experience is that I'd take that situation any day of the week. I can control the quality of the air inside. I can control the humidity. I can control the temp. And all can be controlled better and more easily than any other house I've been in. I'd much rather be able to specify the levels for temp, humidity, pollutants, etc, than have to defend against the constant changes in their levels after the building envelope has been breached. A tight house is not the same as a sick house. A tight house is just that. A sick house is one that was poorly designed or constructed. A healthy, tight house is going to be tangibly, palpably more comfortable to live in than either a non-tight or a sick house.
Is concrete impermeable, Cloud? Or do you use some type sealant one one (or both) surfaces? Water and molds will wick through your everyday concrete, won't they?
Don't forget about the 3"-4" of continuous polyurethane foam, and the air form, and the exterior coatings. Concrete is to the interior for structure and mass. A concrete-only structure would have nowhere near the comfort or control.
Jim
You are correct in your assumtion that concrete isn't impermiable,.... untill you make it so. Normally concrete will wick moisture up from the ground.. If you place the concrete over a 9 mil vapor barrier you avoid that problem and then normal sealing techniques will prevent the moisture in the walls from entering..
ICF's have that wonderfull foam that does such a nice job of being a vapor barrier all by itself. once you coat it or seal it it's pretty free of normal mold problems (mold doesn't find living on plastic as wonderful as living on douglas fir, nothing to eat! ;-)
In addition ICF homes have been tested in winds up to 200 MPH, well over the point where a normal stick built house blows off it's roof and collaspes the walss. thus in tornado alley or along the coast an ICF home might remain standing while a stick built home beomes kindleing..
I think some very good points have been made so far in this thread.
I view tightening of houses as I do most everything else in life. Everything in moderation.
A small bowl of ice cream is better than pounding down a half-gallon per sitting, and having two beers with friends is better than being a falling-down drunk.
What do I think needs to be tight? Cathedral ceilings. I have zero-tolernace for air or vapor getting into a catherdal-type ceiling.
Next down the list? Walls. Dense-pack does a great job of minimizing air movement, but it does allow what moisture that might be driven through the walls to be held, and to eventually dry, without causing any damage whatsoever.
I embrace some leaks.
In my own house I have two wood-burning fireplaces. No glass doors. No sealed combustion. Without a doubt they leak. Could I seal them and make them tighter? Sure, but I'm not going to. I embrace a bit of air exchange, even with make-up air supplying the firebox. Plus, I'll never give up the caveman mentality of enjoying or the romantic opportunitites generated by the crackle and pop of a good wood-burning fire. I don't care it it's a net loser in the BTU department. I like it.
I have double-hung windows. Sure, they're Marvin, which makes a good window...but the best double-hung is still leakier than a tight casement would be. Aesthetically, no one is going to get me to put tight casements on a colonial house in New England.
So what's my standard? Tight, but within reason.
Control moisture entering the house in the basement. Control moisture generated within the house at the source. Control exfiltration through the lid. CONTROL RADIANT GAIN THRUGH THE LID to minimize cooling costs. That is the biggest money-saver and comfort-increaser that I can think of. Embrace RFH over forced air. Keep the feet dry and the head tight. Let the walls deal with the remainder.
Everything in moderation.
Home automation already offers the 100% level of control that you wrote of.
Jim, I think its all about trial & error. People start doing things a certain way to solve problem "X" and then 10-15 years later they discover that they overlooked something with their solution and have created problem "Y". So you find the 1960's houses which were sealed in the 1980's (to solve problem "x", high energy bills) with mold in the wall (problem "Y").
That doesn't mean insulation is bad, it just means they didn't take into account the whole building envelope.
Eventually they get the bugs ironed out of the process and make the problems go away (or create new ones which will eventually be solved). But I think the conscientious builders are slowly improving houses and making them better than ever before.
And while I agree with you that it seems inherently illogical to rely so heavily on mechanical means for ensuring a healthy home... I can learn to tolerate the mechanics when I see my sister's utility bills. During a fairly mild winter month, they are looking at a $300-500/mo heating bill, and if the temp gets below zero, their radiators can't keep up and they either have to set the thermostat at 50, or turn on a bunch of electric heaters (to keep the house in the 60's).
All because she is afraid mold will form if they insulate the walls. And she thinks that old (drafty) windows are 'charming'. In the next year or two we are going to get hit with a "regular" IL winter, and I wouldn't be surprised if their monthly heating bill goes over $700/mo.
Meanwhile, you could take the same sq ft and design it with SIP's, efficient windows, mechanical ventilation ,etc and be looking at less than $100/mo in utilities. To me its worth ironing the bugs out of a tight building environment.
jt8
It's better to light a candle than to curse the darkness. --Chinese proverb
Jim,
While you may have a point where you live, in my climate it can cost over a $1000 a month to heat a home during the winter.. (I know because that's what I pay for dec. thru feb.) In the summer my home is wide open and only on rare occasions will I run the A/C Mold build up? Not if you place the right vapor barrier in the right place..
The flaw is the compromise between traditional stick building and efficency.
Traditional stick building has poor thermal condutivity (or good, I guess it depends on how you look at it) that is the R value of a 2x4 (or 2x6) is so low as to be practically not insulated.. if you look at all the thremal bridges in tradional stick building you'll start to see the probelm.. That is you not only have them every 16 inches and top and bottom plates plus with cripple studs and doubled studs in actual fact it's not hard for a given wall to be 40% wood!
Every time you get that much tempurature variation in the confined cavity of a wall you are bound to create a perfect brewing site for mold.. Add a flawed vapor barrier and wood that is prone to easy decay and there you have the perfect storm of mold making!
There are solutions but it requires radical rethinking of home construction..
In the north the advantages of construction with SIP's should be obvious while in the south construction with ICF's clearly is an advantage over traditonal stick construction.. I think the dividing line should be around Iowa since that is as far north as termites can survive..
Finally, controlling radon is a seperate subject.. even in drafty homes with plenty of air movement Radion can and will cause problems.. In a perfect world we'd simply not build where radon buildup is a problem, Since we all live in the real world then seperate radon management techniques should be used.. frankly the idea of radon problems scares me more than it should, my family's history is filled with cancer and I've used a great number of those tests plus I had an "expert" check my home...
I've wondered the same thing. I'm planning on a tight house, then discovered I have to install an HRV unit to ensure fresh air and to deal with humidity. Even though the HRV will retain 85% of the heat in the house in the three hours it takes to replace all of the air in the place once, I've wondered about the math. What's the difference between a tight (and more expensive) house that loses 15% of its heat to the ventilator every three hours and a not-so-tight house that loses air through the envelope? Am I being sold snake oil?
I have a very tight house.(.76 ACH50). My home has 4200 conditioned sq ft. I bring in 50 cfm of fresh air continuously through a dehumidifier and 95% (almost HEPA) filter. We are in Austin TX. I heat and cool with a 14 SEER heat pump. My average monthly electric bill is under 100$. I maintain the RH at less than 50%. We only have to dust once every month or two because of the filtered incoming air. No snake oil from where I'm sitting.
How large is your new home? How many bedrooms? How many occupants? Fresh air requirements may be less than you are calculating.
2600 square feet. Four occupants (and a dog). The standard is .35 air changes in an hour, and we don't require air conditioning (we're in Maine). We do have some alergy issues, which is part of the appeal.
ASHRAE recommends 15 cfm per person. They raise it to 20 cfm per person for smokers or people with lifestyles that may introduce extra levels of pollutants such as certain hobbies. If we figure yours as five people, that comes to a requirement of 75 to 100 cfm of fresh air. I will assume you have 9 foot ceilings in your 2600 sq ft home. That is a volume of 23,400 cubic feet. Divide that figure by your requirement of 4500 to 6000 cubic feet per hour and you get .19 to .25 ACH. If you have kids opening doors a lot or use a powerful vent hood for cooking, this requirement may be greatly reduced. During times of no occupancy, this requirement is also greatly reduced. The .35ACH figure is a generallized number that is used when calculations are not possible. Your hme can be taylored to your needs and lifestyle.
I recommend increasing this amount for the first year, due to offgassing of building materials. In many times of the years you may be able to simply open windows. The tight house is necessary for times of temperature extremes and poor outdoor air quality.
Being in control of this air in both quantity and quality is a benefit to building a tight home. HRVs have been proven to pay for themselves in cold climates.
Weaf,
Let's assume for a minute that you live in the northern portion of states, where heating is your major concern. Build a home with no way to control heat loss or build one where you can tightly control the heat gain or loss..
Pretend it's 20 below, which do you think will retain heat better?
Sure as it warms up you'll open up the heat recovery unit to admit fresh air and exchange stale air.. But during the cold spell you aren't lossing heat outdorrs..
If you are south then your prime concern is conditioned air and you could reverse the process, ie, open up as it cools off outside.
as for the middle section of the country look at your energy bill and compare them to your energy bill of a decade ago.. see how much they've gone up in 10 years? What in god's name makes you believe that the cost of enegy is going to go down..
Well, I'd do the math as far as your monthly heating and cooling is concerned. I bought HVAC-Calc, which bases its assumptions on ACCA Manual J, 7th ed. IIRC. According to the results, my heat gain or loss due to infiltration was about 1/3 of the total building gain/loss when I selected a normal construction house, vs. less than 1/10th that we tested for.So, if you live in an environment where there isn't a lot of heating and cooling, a HRV/ERV won't do much in terms of improving efficiency. Worse, those running motors add heat to your home, etc.Considering that there are 5650 HDD and 770 CDD in my area, cutting our heating and cooling bills by nearly 1/4 (by going to tight construction and using HRVs to reclaim 85% of the cooling/heating) amounts to a lot of energy savings.
Weaf, I apologize if someone has already covered this, but you are still better off with the tight house. That puts you in control of where and how much air is being introduced into the house. Which means you can filter/dehumidify the incoming air.
And yes, you do need the air exchange so that you can get rid of indoor pollutants. With the various building products, a new house can be off gassing any number of harmful chemicals. The air exchanges allow you to suck that chemical laden air out and bring in 'fresh' air.
The well constructed tight house with the air exchanger is always going to come out ahead of a drafty house.
jt8
Failing doesn't make you a failure. Giving up, accepting your failure, refusing to try again does! -- Richard Exely
"What's the difference between a tight (and more expensive) house that loses 15% of its heat to the ventilator every three hours and a not-so-tight house that loses air through the envelope? Am I being sold snake oil?"Weaf,I just now read through the thread and I didn't catch if you got an answer to this or not.The difference is that with the ventilator, you are in control of the air changes. And it can be altered if your lifestyle changes (or if new owners have a different lifestyle).If you rely on a "not so tight" house you have no control over it and you will be lucky to get the appropriate amount of "not so tight".Rich BeckmanAnother day, another tool.
jim,
Some time back when I was a framing and trim sub, I framed a house for an "old school" builder. He finally did give in and stop using felt as a rain screen and started using Tyvek. After installing the windows and doors (with caulk and flashing) I started to tape over all the nail fins and all seams in the Tyvek. He happened by about that time and inquired as to what I was doing. I explained how I was sealing the envelope. He took the cigar he was chewing on out of his mouth, cursed a while and ask me: How would you like living in a refridgerator?
He proceeded with more cursing and a long speech about how folks in his generation and those before him lived healthier lives although they didn't live as long (probably because they never saw a doctor untill they were too sick to get out of bed and medicine was not as advanced as now days). He raved on about having to open a window to get the door closed, sleeping with a window open even in the dead of winter, or throwing a brick through a wndow to ensure proper ventilation at all times, about how in the old days people didn't seal every little crack and cranny in a building. I thought long and hard about what he said and I've never forgotten the refridgerator analogy.
In spite of the speech, when I build a house now, I seal everything I can. It's all about those energy bills with my clients. The energy crisis in the 70s seemed to fuel the fire, to build as tight as posible. It seems the goal is and has been to be able to heat a house with a candle. I often wonder what the future will show us about the buildings we are building today. I too wonder if we are doing the right things.
And you maybe on to something about the climate computer. If they don't have them now, they aren't far off.
kcoyner
It seems the goal is and has been to be able to heat a house with a candle. I often wonder what the future will show us about the buildings we are building today. I too wonder if we are doing the right things.
I've heard some folks say that a super-insulated, tight house can actually receive a fair amount of its heating from its occupants. People as furnaces. That would be a tight house!
But I think I'd rather have the air exchanger running and make sure the air stays fresh, even if that means I've got to include something other than people as a heat source ;)
jt8
Failing doesn't make you a failure. Giving up, accepting your failure, refusing to try again does! -- Richard Exely
Everything needs to be looked at as a system. It is apparent that making a structure tighter and nothing else does not work. Wood frame construction as part of a sort-of tight structure just causes problems to show up faster. I am a big advocate of super tight and insulated houses that do have air cavities in the walls (for all practical purposes). ICFs, and to a lesser extent SIPs, go a long way towards allowing truly tight, well insulated, and healthy houses to function, providing the rest of the system is designed accordingly.
As my structural engineer said: "I never cared much for building out of vegetable matter."
>It is apparent that making a structure tighter and nothing else does not work.Excellent point. With the earliest of the insulated concrete thin-shells, people would toss in a window A/C and do nothing else, and then wonder about elevated CO levels and mold and such. Mine was one of the first to do more than opening windows for fresh air and to actively address humidity levels and pressurization. Now we know that if it's planned as a system, as you mentioned, that you can get some fantastic results...not sterile like a clean room or smelling of disinfectant (as the hyperbole goes), but just normal, fresh, healthy, comfortable.
The problem around here is that vegetable matter is more forgiving of a seismic event. Homes based on concrete may be great for insulating, noise reduction, fire resistance, and termite resistance, but I'd still think more than twice about building one for myself (other than Cloud's domes, which are a different animal) because they crack and turn to powder in a quake.
Hmm.... the strength of a house vis-a-vis earthquakes is a matter of how it was constructed. It is true that traditional stick-built homes can be more resistant to damage due to their higher flexibility. That is not to say that you cannot build a concrete home to withstand earthquakes, it just means that you have to account for those loads in the foundation design, either by decoupling the foundation from the ground with dampers or by building the foundation strong enough to withstand the forces (i.e. lots of rebar, steel, etc.). I would argue that this is all the easier in residential design where the buildings are not as tall as on the commercial side and hence won't develop as much momentum. Any home built in a seismic zone needs strength in tension and in compression, hence the use of rebar in concrete, it makes it less anisotropic. However, as with all structures that feature composite construction techniques, not only the strength, but also the direction of the rebar or other reinforcement material is critical, to ensure that the tensions developed are absorbed by the reinforcing agent.
I believe you - but the methods you suggest are either prohibitively expensive (dampers) or not well understood. I have seen enough concrete broken away from the rebar to question whether the use of rebar really makes a concrete or brick home earthquake friendly. And I know that my insurance company doesn't care - it is just plain less expensive to insure a framed home than it is a masonry or concrete home in this area.
I don't think that it's a matter of understanding, more one of anticipating. For example, the Kobe earthquake was deadly and it leveled a number of concrete structures, yet modern ferroconcrete structures held up remarkably well, while many older wooden structures failed from shear stress (apparently the heavy tile roofs were a big factor).
If you look at some of the "failed buildings" on that site, you'll see that a lot has to with when the building was built, what the building codes were at the time, and what ground the building was built on. If you live on landfill in a brick house, you better not be home when a earthquake strikes... Incidentally, Boston is overdue for a shaker, and I wonder to what extent Back bay is living on borrowed time.
Anyway, that the insurance company is less than rational with respect to ferroconcrete structures is but a reflection of how crazy the insurance business is, not reality. For example, if given a choice, 'd take a ferroconcrete basement wall any day over a wooden one, no matter what some advocates of such systems claim.
[edited to make the HTML link appear normally]
Edited 6/7/2005 10:05 pm ET by Constantin
Success or failure in the Kobe quake was largely a function of the amount of steel in the building--whether wood or concrete.The older wooden buildings that failed had very few shear walls and metal holddowns and other metal connectors. These days Japanese wooden buildings have as much metal as Dade County buildings, and they do just fine in quakesThe 1981 standard for concrete buildings is 10 cm placement for
rebar. When a post 1981 concrete building failed, it was often the case that the contractor had cheated on spacing of rebar.As for crumbling, however, the Japanese have a huge problem with sea sand, which contains salt. Sea sand causes concrete to crumble. There is an increasing shortage of salt-free sand, and so inevitably sea sand get sneaked into the mix.I haven't heard that sea sand was implicated in failures in the Kobe quake, but I suspect it was a factor.
>I have seen enough concrete broken away from the rebar to question whether the use of rebar really makes a concrete or brick home earthquake friendly.It makes all the diff in the world with our stuff. If one of our shells had no concrete, it'd fall apart in a quake, most likely. With the specified rebar acting as a kind of belt and suspenders, we'll just bounce around with the earth but likely stay whole. Note that the shells don't need much of a foundation at all, be/c the structure itself resists the forces of quakes and wind. All the foundation does is keep the bldg from cutting a hole in the ground, ala a giant cookie cutter.
Cloud,
I remember seeing your 'disaster-proof' home on the back of FHB some time back, which is why I excluded it when talking about concrete structures.
Like I said to Constantin, I believe that concrete structures can be made earthquake friendly, I'm just a little doubtful as to putting it into practice, is all. The flexible sapling surviving the great wind versus the mighty oak that is snapped like a twig. The flexible wood versus the rigid rock. Your domes float atop the shifting sea of ground during an earthquake, and so survive.
Of course most homes around here are built on concrete foundations so it's sort of a moot point - plenty of homes may survive the quake but their foundations will be shot.
Yeah, I know you get it. I'm just trying to put into words why things work as they do...why a structure that's consistent in composition throughout and accounts for compression and tension will typically behave better when stressed than one that's not. But you know, it doesn't have to be domed to have these characteristics. Doesn't even have to be curved. The building code addresses this as "thin shells and folded plates". Here's an overview of some of the shapes: http://www.ketchum.org/ShellTandF/index.html
Here's another natural disaster for you.
If I remember correctly, the NE structure was reinforced concrete. Held up a bit better than the stick builts.
Another point for reinforced concrete.jt8
Failing doesn't make you a failure. Giving up, accepting your failure, refusing to try again does! -- Richard Exely
Hurricane Ivan was a good test case for this, too. A thin shell on Pensacola Beach weathered the storm in fine shape while the neighboring houses were destroyed. The stupid part is that the owners and even a news crew slept in the house during the storm. I wouldn't fear for the structure, but reinforced concrete won't be much help to prevent drowning from tidal surge...unless it held a sizable air pocket, I guess...a little too Poseidon Adventurey for me.
Earthquake damage can be broken down into two categories: to the structure and to the stuff inside.Concrete (and red iron) structures are much more susceptible to the latter kind of damage than wooden, since they shake things up inside more violently. I am sure this must figure in insurance rates.However, in Japanese quakes at least, the real damage occurs after the quakes when all that wood starts burning, due to gas ruptures (and people setting fires for the insurance).
"The problem around here is that vegetable matter is more forgiving of a seismic event."
True, but reinforced concrete is very good. After all, all the foundations are concrete and stick construction on top of a pile of failed concrete would not be much good in an earthquake either.
I am building an ICF house 5 miles from the San Andreas Fault and have done a lot of homework. Modern one and two story concrete structures that are reinforced anywhere near today's codes have done very well in earthquakes around the world.
I don't know about houses so much as non-residential buidings, from the standpoint of the cost to heat, cool and ventilate. I have witnessed the progression of the industry over the same period of time as you speak and know the recent history before that.
In a nutshell, the commercial buildings presently being built today, do not save a significant amount of energy on the HVAC side of the equation, unless energy recovery and/or thermal storage and passive systems are all incorporate into the buidling design.
In the 70's, especially after the oil embargo ventilation rates were cut to save energy and buidling were similutaneously built with tigher and better insulated envelopes. Add to that, the "new" products such as carpeting and accoustic tile ceiling panels and gypsum wallboard. Subsequent to these building practices and management we started to develop "sick building" and we started to be very efficient at growing mold indoors. Then, as we discovered that humidity control and fresh air were important to the health of people, the pendulum began to swing back. As the present ventilation rates were incorporated into designs, some 15-20 years ago, the capacity (and cost to operate) of the HVAC systems nearly match those of similar sized building from the 60's. The only difference is that present equipment does the same job or nearly so at a more efficient rate.
Well, I think it depends...Commercial buildings for the most part were/are being built with the lowest per square foot cost as the prime directive. In an age where heating/cooling/etc. are an insignificant cost of doing business and where most businesses lease their space (and hence lose control over the infrastructure), there are no good incentives to improve the envelopes.However, those businesses that have made a point of reducing energy footprints, usually find lots of areas to do so. Yet, considering the very low cost at which energy is being sold to them, there is little incentive/payoff to do better. The technology is there.... 98% AFUE boilers, high-SEER ACs, desuperators, CF lighting, etc. but few want to apply it. Nevermind the possibilities of building efficient envelopes that cost a neglible amount more to build but which will require far less energy to maintain comfortable. Easy things like awnings, etc. block summer sun while allowing the sun to warm the place during the winter... etc.I predict that when the costs of energy impact businesses beyond the 1-2% they currently cost (in terms of revenue), that more businesses will wake up and some may even be able to justify easy fixes like TRVs on radiators, envelope improvements, etc.
It DOES depend, but focusing on the envelope and uneconomical technology (i.e. give me an example of a 98% AFUE boiler capable of 2,000,000 btu/hr output) that is not utilized at this time, and not what a great deal of the operating costs are: ventilation, is where the disconnect is. Efficiency improvements that apply to real world then vs now are AFUE has gone fro 65 to 80% and EER has gone from 6 to 8.5
The costs associated with conditioning more outside air to maintain air quality offsets the much of the savings that are due to increased envelop efficiency, in most cases.
Take a 200,000 sf multistory office building. Brick and Block 1950's contruction with the basic vent requirements of the day (about 10 cfm/person) and 7 people/1000 sf.
The walls have an r-value of 3.5 and the T&G roof with fesco board had and r-value of 13.5, single pane windows with an r-value of 0.09 (u=1.1).
This building would require boilers wiht an input of 15M MBH including ventilation and 725 tons of air conditioning also including ventilation for 1400 people (15,000 cfm).
Consider an equal sized and occupied buiding under current codes and built in a standard fashion. Walls are r-20, roof/ceiling is r-30, windoes are insulated double pane. Ventilation requirements (due to the results of lower infiltration and modern material) are now 20cfm/person. The maximum loads for heating and cooling would now be 12M btu/h and 625 tons, respectively, including ventilation for 1400 people (which now is 30,000 cfm). Noticeable improvements no doubt but not the 50+% improvement that you would expect from the greater envelope efficiency.
There are many ways to improve upon these costs, but these technologies are not selling. One reason is simple expense, many can barely afford to build, much less build for efficiency. (I live in N.IL where heating costs are significant but all the new vinyl sided houses sprouting up like weeds have the cheapest 80% furnace and gravity vented GWH's you can buy) Another reason is that the developer seldom occupies the structure that they are paying to build and therefore doesn't care about the operating costs, only the capital costs.
Timbo,There are boilers in that capacity range with AFUE ratings of 96%+, like the Vertomat series from Viessmann. As with all condensing boilers, the trick is to have a building where the return water temperatures are low enough to take advantage of the condensing feature. Another way that many contractors are achieving 2MBTU boiler installs is via systems like the HTP's Vision 3, which allows you to strap a whole bunch of 399's together for awesome modulation range and redundancy.EER ratings have also steadily climbed. I am about to install a 14.25 EER rated Lennox system in my home (which is over 20 SEER). So it can be done. Plus, if you plan on living in a particular area for a while, it even makes economic sense (our electrical rates are the 2nd highest in the nation).The crux is, like you pointed out, that developers generally do not live in the homes they create. The chase to the lowest common denominator is on from the outset... However, if the Feds or whoever mandated a tighter envelope, that basically set goalposts into the ground as far as ACH infiltration, BTU/(sq ft x HDD), then every builder would be playing on a level playing field. The incremental cost of doing it right is miniscule on a project scale. For example, the entire insulation package came out to less than the lighting on the first floor.So, is the end cost of a structure that much higher as a result of better infrastructure, insulation, etc? The data that building science corp. has collected seems to indicate that the payoff of going with a tight envelope is positive most of the time, even on an installed-cost basis, because of the cascading benefits of tight home construction. I look to people like RayMoore who can maintain a comfortable home in the blazing TX sun for a $1/day, for example.In my mind, it is foolish to spend the money on a home that you cannot afford to build properly. Either do it right, or don't do it at all, as the operational costs will always be higher than you expected. Plus, the energy savings are a tax free addition to your wallet.
Jim,
I just read through about 89 posts here-------
and although they were interesting----they all discussed treating the symptom---and ignored what I think is the real problem.
within the last 3-4 weeks or so I read an article in my local paper( which I now wish I had saved LOL)
The basic point of the article was a discussion of a " theory" put out by a gentleman some 50 years ago or so. At that time----the gentleman looked at petroleum production, reserves etc and predicted that somewhere between now( today) and about 20 years from now petroleum production would peak----------------
Once we hit that peak( and we are either at it---or very VERY close to that peak)---the theory was that society would undergo a radical shift encompassing everthing from where we live, how are houses are built, how they are heated, how cars operate etc.
now-----look at average new house size---the sq. footage of those " levittown post war Capes" in the late 40's and early 50's--------- the " ranch' style houses of the 50's and 60's----------- the Ryan Home Colonials of the 70's and early 80's with the attached garages and 4/12 pitched roofs---all the way to the horiffic McMansions of the 90's and today.
I suspect sq. footage has at least doubled since the 70's---and probably nearly quadrupled since " levvittown"
Has this same explosion in house size occurred world wide---I don't know--but I bet not. Why do we americans think we are so " entitled"
Is it remotely reasonable for a family of 4 to put up a 3000 plus sq. foot house ?
Was it a smart move to develope infrastructure to encourage widening ring after widening ring of sub-urbs?
Is a 30-40 minute commute EACH WAY to work a smart idea for Joe Cubicle Dweller?( and lets not forget Joes' wife Susie Soccer Mom---also working outside the home and with a similar commute------------Plus their kids who take a school bus everyday 'cause they live so freakin far from school that they couldn't walk there if they wanted to---and there aren't any sidewalks in their subdivision if they tried to walk.
I could go on and on--------but isn't striving to build a " tight house" really just "whistling in the dark as we walk past the grave yard"----aren't we ignoring what;s really going on---and what's really gonna happen? when gas is $8/ gallon?, when the rapidly depleting aquafiers in the south west give out? when the inner city poverty class can no longer be ignored?, when all the jobs have been outsourced??????
BTW---Jeff Buck will be sitting pretty in PA, with a manageable sized house, plenty of water, and hordes of people moving BACK into the city. LOL
Stephen
Average house size in developed world is somewhere under
1200 s.f., the same as America in the early 50's. These
numbers are skewed somewhat by inclusion of apartments, though,
which tend to be smaller.But I thought I read somewhere the other day that the trend
had turned in the United States, smaller houses were coming
back into vogue (along with the move from SUVs to hybrids).In a world of $8 per gallon gasoline, houses withing walking
distance of a light rail station will have a premium price.
In a world of $8 per gallon gasoline, houses withing walkingdistance of a light rail station will have a premium price
There's a bunch of suppositions, there. Like the light rail goes where the work is. Might be tough for a framer to ride mass transit to "work."
The harder part for mass transit, is that it also requires (for best efficiency) having a lot of common employees to share a home neighborhood, too.
The "peak" article was intersting when it came out. The timing was inoppertune, that was the same day the wildcatter hit a multi-million barrel reserve in either Wyoming or Utah. The same week, the Russians said that they had found new fields in SW Siberia, too.
That's the problem with the future--it's a lot more clear once it becomes history.Occupational hazard of my occupation not being around (sorry Bubba)
Gas might hit $8 a gallon, but if it does, it is unlikely to be because of the cost of crude. There are several technologies that allow us to turn garbage into useable fuel. So far, the biggest problem with them is that the oil they produce costs more than $80 a barrel.
The price of electricity keeps going up. The price of solar cells keeps coming down. There will come a time when it makes sense to just add more solar cells to your house. - Unless fusion power becomes a reality and throws all of that out the window.
fusion power is getting closer. When it does, a gallon of heavy water at $200 will produce the same power as a million barrels of oil.
If electricity is cheap enough, fresh water also becomes cheap.
many inventions on the horizon are going to interact in ways we never dreamed possible.
Actually, the average cost of solar panels has increased each month for the last 13 months. I foresee a cheaper panel on the horizon when nanotechnology is used to make a new more efficient panel at lower cost to the consumer. It just hasn't made it to the market yet.
You can monitor solar panel prices at this website.
http://www.solarbuzz.com/Moduleprices.htm
Hello, Jim.
I was struck by your post (and the replies) as published in the November magazine about tightly sealed homes. "Kcoyner" asked if we would like to live in a refrigerator because of how we tape and seal everything. The replies to your post show that many do not understand the reason for sealing homes tightly. The fact is we did not change to living in refrigerators because of tightly sealing our homes. We changed to living in refrigerators when we demanded air conditioning. Air conditioning IS refrigeration!
Now think about your refrigerator. Where does mold grow most often? Around the leaking door seal. Why? Because warm, moist outside air is leaking around the cold surface of the refrigerator. This is the exact same cause of mold and stuffy odors in homes. What is the solution for fixing the mold on the refrigerator? Improving the seal. This is the same solution for fixing the mold in homes. Another reason you want to have a tightly sealed home is that the inside of our walls and attics are filthy. Any drafts that leak through the walls, floors, and ceilings carry dust, powdered insect feces, and fiberglass fibers. Yuck!
But no one wants to live in a stuffy, air tight box. There are several sollutions. One high technology solution is to open the windows when its nice outside. If you want an automatic system, your air conditioning can include a device to draw in outside air through a filter every time it runs. Both systems work very well.
But there is a better solution. We could design homes that stay comfortable without refrigeration. By using the power of the sun, the earth, and the physics of air and temperature flow, we can design homes that cost nothing to heat and cool, without breaking the construction budget. I'm talking about solar heating, earth berming, passive cooling, better insulation, and many of the other great ideas being used today. Its time to rethink how we build.
Mountain House Plans by Richard C. MacCrea
Hear Hear...Building an energy-efficient, strong home doesn't have to break the bank as the multiple case studies at Buildingscience.com have shown. If we can reduce the need for heating and cooling through exterior design features, then we can reap the benefits of the domino effect as utilties, etc. inside the home shrink. Trouble is, many homeowners so far don't pay enough attention to the details inside their homes. They worry more about the appearance and how much they can impress their friends than the electrical, heating, etc. needs. Showy fireplaces are cheap to retrofit later. Reinstalling or retrofitting insulation, now that's a big, messy project.I imagine that the coming heating and cooling seasons will start to change people's preceptions and make energy-efficient cool again. Our local electrical rates are slated to go to $0.20 a kWh, gas will be about $1.71 a therm, and #2 oil is still above $2.20 per gallon. Hit 'em in the pocketbook... then let the market find the most efficient solution.
Oww! $.20/kwatt! In BC, electricity is just under $.07 CDN, mainly fuelled by hydro dams, and combined with mostly above-freezing winters, electric baseboards are still king here. We are VERY fortunate!
Nice message but, if you live in a hot humid climet on the Gulf or Atlantic Coast some of the energy savings you are speaking of are not as easy here as in higher locations. 75 ground water, 80 dry bulb, 95% rh and this is at 8:00 am most days of the year. I will speak more on this later. I am planing a new home to be started early in 2006. It will have ICF outside walls Steel roor and steel truss. Roof insulation will be iceyene. The cooling/heatingwill be earth coupled, geothermal heat pump. Outside air will be controled for proper IAQ ( 5% - 20% ). Hot water will be A/C heat recovery and solar. I will send more info later.
Hello, Don.
I used to design homes for central Florida but fifteen years ago my designs were not nearly as green. So, my green experience is in the mixed climate of the southern Appalachians.
Having lived in Florida, I don't mind the humidity, and have contemplated the idea of designing a passive cooled home with materials that would not be adversly affected by humidity. The model home I am currently building is ICF and we are finishing the walls with homemade lime plaster. Proponents claim that this is an excellent humidity battery, and this alkaline material will not support mold growth. We are mixing pigment into the plaster and achieving a beautiful wall that resembles polished stone. You can explore our project online at http://www.mountainhomeshow.com This is a learning project and since it is my own home and office I can afford to experiment.
There are new geothermal systems out that send the freon through the ground which is far more energy efficient than using a fluid and an exchanger.
I wish you success with your project, and I am interested to know how it turns out.