Anyone have any recent info on the cost of sprayed-in expanding foam insulation, particulary in the 2X6 exterior walls? Unless the price is comparable, I would probably use batting for the 2X4 interior walls.
Thanks.
Anyone have any recent info on the cost of sprayed-in expanding foam insulation, particulary in the 2X6 exterior walls? Unless the price is comparable, I would probably use batting for the 2X4 interior walls.
Thanks.
Learn how to plan, fabricate, and install a chute to conveniently send your dirty clothes from an upstairs bathroom or hallway to your laundry room below.
"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.
Get home building tips, offers, and expert advice in your inbox
Fine Homebuilding
Get home building tips, offers, and expert advice in your inbox
© 2024 Active Interest Media. All rights reserved.
Get home building tips, offers, and expert advice in your inbox
Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features.
Start Your Free TrialStart your subscription today and save up to 70%
SubscribeGet complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine.
Already a member? Log in
Replies
It's about a third to half again as much. The advantages are that you don't do the insulating, it gives a higher R-value for the amount of space, and it actually adds structral integrity to the house. For that last reason alone it's especially good for older under framed homes.
Thanks,
This would be new construction, but I'm sure it would give us a much tighter house.
Corbond out here costs about $2.50/SF for 3" and $3.50 for 4". Icynene about the same.
Considering the batting for 6" is about $.51/SF, that's quite a difference. What's the current cost of installing the batting, I wonder.
FG batting is cheap...and you get what you pay for. With FG you get to keep paying each time you get a heating bill.Garett
Yeah, no heating bills with foam insulation. Yeah.
When I priced spray in foam it was about 2.5 times the cost of fibergalss. Regarding the install costs of fiberglass, I find that I can hire an insulation company to do the work for maybe $200 more per house than the material costs. You need to do some kind of cost analysis and factor in how long you think you are going to be in the house to determine if the foam is cost effective for you. Your climate will definately come into play too.
How long you'll be in the house is irrelevant. When you walk through a house built with foam, the quiet alone can help sell the house. Efficient houses will be even more valuable in the future. Utility bills are a selling point when a home is built right. Making decisions like this based on a short time line is irresponsible. I hope you will reconsider your position. You are in a position to make a difference.
I typed a big long response. Hit the post button and got an error message.
I'm not gonna retype the whole thing.
Here is the summary. Builders must build what sells. If their houses don't sell, they don't eat.
Matt,That is true, but if a builder builds a better(more efficient) home he may have to "sell" the first few, but after that the recommendations and referrals will sell for him(her).People who want cheap....always pay for it.Garett
How does that work for you? Good I hope. Tell us about your successes in selling well insulated homes.
In the previous post I said I typed a long response and then got an error message when I hit the post button.
A few things I said were:
The company I work for used to have a Energy Star home program. It died. Why? Didn't sell. Costs maybe 5k per house depending on the size - about $7k to the customer. Maybe the climate is too moderate here for people to think much about fuel efficiency. I built 14 of them for another company I used to work for, so I have a good base understanding of energy efficient construction. The program was being partially funded by some kind of state or federal program - can't remember which. They don't do it anymore. BTW - the Energy Star certification company felt that fiberglass was adequate for our climate.
Home buyers in this area would rather have a room of crown molding than R-38 in the attic for about the same cost. 98% of them don't know what R-38 means. The insulation is on the price list, but very few buy.
These things could change if the change was legislated. As it is the IRC2003 (with modifications) has been hung up in the legislature for a long time. Someone told me that it will more or less mandate low-e windows. Fine by me.
"I" have a new house that has been sitting for a year. It's in a town about 40 minutes form here. Only thing I can figure is that I didn't build it cheap enough for that market. It's a rather modest house of 1344 heated sq ft. Currently, it's just a liability. Glad it's not taking food off my table. My wife and I have to budget on groceries as it is.
If I had a client who wanted to pay for a well insulated house I'd jump at the chance. A lot of what we sell are specs though.
My personal home is built to Energy Star specs without the certification. In the next home I build for my wife and I, I hope to use foam. I have to sell her on the idea too though which I probably can.
I'm sorry Matt. I shouldn't let my ideology trample on your reality. Perhaps I should just nudge at it a bit.
Energy issues are going to become increasingly urgent, and folks in the building industry can have a major impact on the efficiency of the buildings we build. It's important for as many of us as possible to push our customers past this "I'll only live here for 5 years" mentality and get them to embrace things like better insulation, photovoltaic, etc. It's not an easy sell but more consumers are becoming aware of the issues. For that matter, so are builders.
Funny that you mention photovoltaic. Very good analogy to the foam issue. So many people on this board seems to attack anyone who would dare mention FG. Then they say "foam saves you so much", ratherly any specific calcuations including NPV analyses. Most push the foam on FAITH, spend the money and you will make it up in the end. Well, maybe, maybe not. Where is the analysis?
Using the same logic we should all light our houses with photovoltaic cells. Afterall, once you spend the initial $40,000 for the system you have no annual electirc bills. END OF STORY. Right? Well, considering that you could keep your 40 grand, buy corporate or tax exempt bonds, earn 5 to 7% on the money, which would be $2,000 to $3000 each year and sepend . . . what half or less of it on juice. It would not be very bright to get your power in that manner.
Not saying that foam does not pay. I am saying that the foam lovers are OFTEN (not always) an angry bunch, attackers, and don't offer facts and figures.
I don't disagree with your investment strategy, but it's not energy policy, which is what I'm talking about and what I think is important. We are going to HAVE to become a much more efficient nation in order to survive economically. The short-term amortization of a PV system or a well-insulated house has to start taking second place and long-term realities have to become number one. It will probably take major incentive programs to get some of these technologies into widespread use.
Now, this is a market economy and of course Americans, in their typical short-sighted me-first way will continue to make self-serving decisions about energy use, and we're all going to get a spanking as a result. I don't read USA Today often, but their cover story Friday was about projected population growth in the U.S.... and they say we'll be at 400 million by about 2040. We will all be forced to adopt much different ways of living if we're going to have heat, light, transportation, clean water, clean air, green space, etc., with that kind of population pressure. Statistically I will be alive in 2040, so I have some concern about these issues.
Pretty nice psot davidmeiland,
But I don't beleive you can throw economic anaylsis out just becuase you say we should throw it out. It is what it is. If heating a house "costs less" over time, and I mean over the life of the house, than the cost of a better insulation, then the RIGHT thing to do is use a lesser insulation. NOW the kicker is that in order to make that analysis and the proper analysis you need to forecast the cost of heating that house. ANd if energy costs rise, and surely they will, it makes the analysis difficult. This is further complicated in that money spent ten years from now impacts teh equation less than moeny spent, five years from now and clearly less than two years from now. This is called discounted cashflow analysis.
As far as population growth and resource utilization etc is concerned, clearly things will change. I don't see any major problems, however. Well, I do bemoan the impact on my hunting and hiking activities and presure on open spaces. BUt as far as resources, the market will drive it. We have seen it already. People screamed adn hallered about oil and hybrids and hydrogen cars. Calling for government subsidizes to promote the change. Then oil shot to $70 a barrel and people stopped buying SUV and started buying hybrids. The impact of the goverment forcing teh change or subsidizing the change would only have lowered our standard of living. How is it that I say that? Well, becasue if you force me to spend more than necessary on product A (whether buy mandateing that I buy a more expensive option like a hybrid over a gas burner or taxing me and makign the hybrid competitive through a subsidid (spelling?????), then I have less money to buy CD, video games, lattes, etc.. The market will get us there when the market gets use there.
Just like someday, two hundred years from now when all the oil is gone and coal is getting in short supply, clearly nuclear energy wil be comparitively cheap and perhaps even solar cells on every roof top will be comparitively dirt cheap as well.
Did you see that current movie: Flags of our Fathers? There were 3 main guys. One guy prospered, one got by, and one ended up dead face down in his puke. Guess which one had the best ideals :-) Be it true, that guy #3 had other issues... You get the idea though.
I'm just a regular guy who would like a new pickup but can't afford one like 1/2 of the other pro construction types on this site.
Don't get me wrong. As far as I know closed cell foam is the best insulation material going from strictly a performance standpoint, and it might even be the only way to go, if say, I lived in Canada. The thing is, this web site seems to always focus on what is best. That's a good thing, only after a while there is no challange in just knowing what gives the best performance - no expence spared. Unfortinately, in the real world there are real budgets, and real people have to shell out the real $$$ to pay for them. Decisions have to be made. Foam insulation makes great "cents" in some situations, just not all.
Very nicely said. Clearly with more patience and tact that some. Hmm, who might that be?
The systems I use are not cost prohibitive. The foam panels I use are 80 cents a square foot. The membrane I use on the walls is 35 cents a square foot. The performance is superior to a 2x6 wall but can be used on a 2x4 wall. I'm building a lowcost structure to house a homeless woman right now using this system. The HVAC system can be substantially reduced in size. Overall cost doesn't have to be higher than any other well built home. It is an overall package. The savings in some areas pay for the improvements in other areas. Gotta go. I'm highjacking the thread again.
That's OK Ray, it's a good hijack. Kinda like taking over a planeload of tired travelers headed to Minnesota in January and forcing the pilot to fly to Hawaii and making the flight attendants give everyone an umbrella drink and a pair of baggy shorts to wear to the beach.
OK - you got my interest. I *think* most everyone was thinking sparyed in foam. Sounds like you are talking about something totally different. Tell us about these foam panels. Sounds like rigid foam? Installed between the studs? as sheathing? SIPS or what? XPS, EPS polyisocyanurate or what? And what kind of membrane?
Here's a cut and paste of something I wrote earlier on this board. I've edited it a bit.
THE EXTERIOR AIR BARRIER APPROACH TO CONSTRUCTING A HIGH PERFORMANCE BUILDING ENVELOPE.
<!----><!----><!---->
BY RAY MOORE<!----><!---->
<!----><!---->
I would like to discuss the exterior air barrier approach to building an air tight building. This approach to air tightening is an alternative to the drywall air barrier method. This method is used in structures with unvented attics as a partner in the high performance building envelope.<!----><!---->
<!----><!---->
There are variations of this application, but I will discuss two methods. In my hot humid climate, I have used the first method with great success. This first method is definitely not recommended in a climate with average monthly temperatures much below 45 degrees F. The second method is safe to use in any climate from Fl to AK. There are few building methods that are appropriate to any climate but I believe this second one to be just that.<!----><!---->
<!----><!---->
The predominate air tightening procedure in the US is the drywall air barrier approach. With this method the drywall acts as the air barrier. There are many problems with this and the devil is in the details. Let me just mention a few areas where this method is impractical. <!----><!---->
It is very difficult to seal plastic electric boxes to gypsum dust with latex caulk. If the wire penetrations were ever sealed, the electrician will compromise that seal when installing the electrical device. <!----><!---->
Intersecting interior walls break the continuity of the drywall and allow leakage. <!----><!---->
When stairways are built on exterior walls, the drywall that is installed behind the stair stringer is virtually impossible to seal.<!----><!---->
Furr-downs on exterior walls are generally sealed for fire-stopping but not to be air tight. The gaps that are left allow a path from the wall cavity to the attic and to the exterior.<!----><!---->
Exteriors sheathings and drainage planes are built with an eye towards water intrusion but not air tightness, so failures at the drywall allow air to leak in or out easily through the exterior skin. <!----><!---->
Bathtubs on exterior walls are difficult to air seal with a drywall air barrier due to construction sequencing.<!----><!---->
Bottom plates are sealed with foam which is often removed by the carpenter running baseboard.<!----><!---->
Floor cavities between floors are very difficult to seal and are almost impossible to inspect, which brings me to....<!----><!---->
Current air sealing methods are tedious and impossible for a superintendent or building official to fully inspect.<!----><!---->
With the drywall air barrier approach, there is a requirement that the drywall on exterior walls be applied with a sealant to exterior walls to avoid wall cavities being connected to adjacent cavities, which allows a path to the exterior. I invite anyone to make the claim that they adhere (pun intended) to this guideline. Most builders have never heard of it.<!----><!---->
<!----><!---->
Modern homes are tighter than older homes due to attempts to overcome these deficiencies with sealants and foam applications at penetrations and around windows and doors. We have invested a lot of effort in trying to create tight houses and have still failed to do so. Blower door testing on new construction consistently illustrates our failure to achieve a truly tight building envelope. The results of this failure are higher levels of moisture in the south, over dry houses in the north in the winter, frequent dusting, higher energy bills, and introduction of outdoor allergens.<!----><!---->
<!----><!---->
PERSIST is a method of applying an air barrier to the exterior of the structure. The exterior side of a wall is simpler, has fewer penetrations, and is protected from being compromised later by the homeowner or remodeller. The methods I use are borrowed from the developers of PERSIST. This system was first proposed in the mid 50s by Neil Hutcheon.<!----><!---->
<!----><!---->
In the first method, cellulose insulation is used inside the wall. The exterior of the wall is covered with plywood or OSB sheathing. The entire surface of the wall is then covered with a rubberized asphalt membrane. A foil face can be included as an outer face when appropriate as a radiant barrier. The rubberized membrane is turned into window and door openings and with the help of flexwrap, and a sloped bottom sill creates a pan flashing. A loose flap is left at the top of the window opening and is later used as a head flashing. A felt fabric wicking strip is attached below the window that extends into the window pan to allow water from a leaking window to escape to the exterior. After windows are installed, a 4" strip of membrane is adhered to the bottom of the window over the wicking strips and down onto the wall. More strips are applied up the sides and are capped by the head piece that was left earlier. This seals the window in from the exterior, providing a superior barrier to air and moisture, while the wicking strips allow water from a window failure to escape to the exterior. Interior air sealing methods are foregone and the time and money is put into the exterior. Inspection is very simple with this approach. The membrane is run down onto the concrete slab and sealed to the brick ledge, or overlaps the waterproofing that extends from below grade in a pier and beam or basement structure. At the top of the wall, the membrane extends up to the bottom of the roof decking and is cut around rafter tails where it is sealed with asphalt based mastic prior to soffit installation.<!----><!---->
<!----><!---->
The second method is similar to the first with one big difference. There is no insulation used inside the wall cavity. Instead, we use a 2" layer of polyisocyanurate foam on the exterior. A foil outer face is used as a radiant barrier and to limit off-gassing of the foam. Window and door openings are oversized and lined with a 2x6 that is installed out to the level of the face of the foam. This 2x6 allows the windows and doors to be installed at a typical plane for siding or stone. Brick lugs are poured with a 2x8 instead of a 2x6 to allow for the thickness of the foam. Special masonry wall ties are attached with 3 1/2" screws through the foam. On sided walls, a 1x2 furring strip is screwed to the wall with 4" screws as a base for the wood siding. EIFS may be used but real stucco is more difficult with this system. We have not yet used stucco over the foam sheathing but it has been done for almost 10 years in Canada. This system is commonly used in Vancouver to correct the huge problem they have had there with water intrusion through stucco. <!----><!---->
<!----><!---->
The wall has the appearance of a 2x6 wall thickness with the lumber costs of 2x4 construction. There is very little thermal bridging. Fasteners that penetrate the membrane are self sealing, unlike other house wraps. Mechanical and plumbing penetrations are easily sealed to these membranes, unlike other housewraps and felt paper.<!----><!---->
Moisture and condensation problems are eliminated and all lumber is kept at room temperature and humidity levels, year round. All drying is to the interior. Wetting is exclusively limited to anomalies such as plumbing and roof leaks. Plumbing can now be safely placed in exterior walls without fears of freezing. The advantages are numerous and the air tightness is phenomenal. <!----><!---->
<!----><!---->
Blower door testing on these structures ranges from .75 to 1 ACH at 50 Pascals. Mechanical ventilation is required and with proper filtration of the outside air source, dust and allergens are substantially reduced. All infiltration is now from back draft dampers and windows and doors. Infiltration through the walls is eliminated.<!----><!---->
<!----><!---->
We have had great results with this system and are continuing to refine it as we go along. My personal home is 3900 conditioned square feet and has an average energy consumption of 1050 KWh and 10 gallons of propane per month. This includes minimal use of fluorescent lighting and pumping the domestic rainwater through an ultraviolet light. We use a hot water circulating loop on a timer and have an eight year old refrigerator that could be improved on. These factors push the parasitic loading to 10 KWh per day. Peak usage in July, August, and January average about 1200 KWh. On a day that reaches 100 degrees, we can turn the AC off for 12 hours while we are away and only experience a 2.5 degree rise inside the house. On a 108 degree day we experienced a 3.5 degree rise. We use a 14 SEER heat pump and a DEC ultra-aire UA150H dehumidifier to maintain the relative humidity in the house to less than 50% year round.<!----><!---->
<!----><!---->
Construction costs are surprisingly reasonable due to offsetting savings from items like IC rated recessed cans and attic ventilation that is no longer needed. Simplified pan flashings and head flashings at windows and doors is also greatly simplified. There is, of course, a learning curve for the trades in the field. <!----><!---->
Sorry for the length. I don't have a website to link to.
That's very interesting.
A few Qs, but first was >>Sorry for the length. I don't have a website to link to.<< the end of the message? Just want to make sure I saw it all.
On the 1st method exactly what is the ruber like exterior membrane? How long has theis method been in use?
On the 2nd method with the rigid foam, is there the exterior ruber like membrane or is that only on the first method?
On the 2nd method, if there is no exterior membrane, how is the exterior of the "sheathing" detailed? I'm guessing you selected the polyiso rigid foam because it has the highest R-value/inch? Are you using diagonal let-in corner bracing or what?
Do you typically use ERVs with these methods of construction?
You got the whole message. I'll post some details later but my wife is hollerin' for me to come watch a movie.
Could you please answer my questions from the 80566.38 post above?
Thanks
That's very interesting.
A few Qs, but first was >>Sorry for the length. I don't have a website to link to.<< the end of the message? Just want to make sure I saw it all.
On the 1st method exactly what is the ruber like exterior membrane? How long has theis method been in use?
On the 2nd method with the rigid foam, is there the exterior ruber like membrane or is that only on the first method?
On the 2nd method, if there is no exterior membrane, how is the exterior of the "sheathing" detailed? I'm guessing you selected the polyiso rigid foam because it has the highest R-value/inch? Are you using diagonal let-in corner bracing or what?
Do you typically use ERVs with these methods of construction?
I'm sorry it took me so long to respond.
If the insulation is located in the stud cavity, then the membrane must resist heat and UV. For this application, I use Peel-n-stick by Polyguard. It has a foil outer face that also offers the benefit of a radiant barrier if an airspace is provided. This product costs 100$ for a 150 sq ft roll. It was designed as a roofing material for mobile homes and is also used as a vapor barrier for rooftop duct systems.
If the insulation is placed on the outside of the structure, then the membrane is protected from heat and UV by the foam insulation. In that case a less costly product can be used. I use Polyguard 650 for this application. It costs 65$ for a 200 sq ft roll. It was designed as a waterproofing membrane for basement and other applications.
The exterior foam I use is polyisocyanurate because of it's superior r-value per inch and it's foil outer face. It is similar to EPS in cost.
In both sytems, the entire structure is first sheathed with plywood or osb. I started using this method in 2001. It has been used in Canada for many years. It is the preferred method for dealing with the water intrusion issues that have caused so many problems in Vancouver.
In any airtight building, mechanical ventilation is very important. I have used ERVs but I prefer to use a DEC Thermastor Ultra-air dehumidifier/air purifier. In my climate, interior humidity levels can be a problem. An ERV can reduce the amount of moisture that is introduced by ventilation but cannot control moisture levels. The Ultra-air will bring in a controlled amount of outside ventilation air through a 4" 95% air filter and mix it with indoor air before distributing it throughout the house. It can also remove humidity when needed, especially during the spring and fall when the cooling load is not always adequate to provide moisture removal through air conditioning.
We have been very pleased with the results.There is only one planet earth. How many chances do you think we get with her?
thanks for the info.
Ray, what system is that? Did you lay it out in detail in anohter post? If so where? I would be interested to read it.
I call it REFORM which stands for Rigid Exterior Foam Over Rubberized Membrane. Chris Makepeace et al call it PERSIST which stands for Pressure Equalized Rainscreen Insulated Structure Technique. It was originally developed by Niel Hutcheon. Read his ideas about exterior walls here http://irc.nrc-cnrc.gc.ca/pubs/bsi/82-1_e.html among other places. Gus Handeford is another author of note on the subject. Google them and you'll find the source of many of Joe Lstiburek's ideas. Joe is adament about them getting credit where it is due. Hutcheon did his work in the 40s, 50s, and 60s. The answers to all our exterior wall issues were given to us back then and we as an industry listened to the manufacturers instead. Give me one good reason why Tyvek should be used in the south.
It is a concept more than a system. Lstiburek likes my acronym but points out that the insulation doesn't have to be foam. It has been done with Rockwool.
Matt,We actualy do the insulation in homes for the areas top builders. It is a sell job at first but the referals do come.People who live in their big trophy homes in northern Michigan are becoming more and more concerned about the heating bill and the comfort level in the house.About half of our volume each year is for highend buliders who are return customers.The other half is small and med homes where the OWNER has done the research and wants our prodct/service. They are the ones paying the heating and cooling bill.Garett
Maybe it will become more common in the south sometime soon. I hope so.
Money speny on FG is wasted.
Better spent on beer, at least you'll get some good out of it.
Joe H
Sorry,Kind of got off topic on the FG is worth what you pay (or less) thing. In my area 1/2LB open cell foam is going for about 2.25 sq in 2x6 walls. A whole house can be less per sq ft.FG is cheap to install, a laborer and a staple gun cost about $120.00 a day.
A foam rig cost that to drive to most jobs.Cellulose dense pack/wet spray are two more cost effective alternatives. Both are $0.90-$1.10 in my area.Garett
ownerbuilder,
Fiberglas is a real fooler.. it has a decent R rating but what they don't tell you when they speak of R ratings is that it's tested in a labratory under carefully controlled conditions..
It's tested at 70 degrees. !
Scary isn't it?
as the temps drop the R rating does as well.
you see fiberglas isn't any sort of air barrier. that's one reason they make furnace filters out of it..
I'm sure you took science in school. You remember of course that warm air rises and cold air settles.. (principle of hot air ballons)
Thus the cold air on the outside wall rises and the warm air on the interior wall sinks (sheetrock side) . It does that in the wall cavity.
the result is scrubbing and the colder the outside temp the more the effect..
Below Zero Fiberglas has a near 0 R rating..
Celluliose doesn't suffer to the same degree from scrubbing especially densepak celluliose.
Sprayed foam doesn't transmit air thru it. So no scrubbing occurs..
Fiberglas is also subject to moisture.. Moisture dramatically lowers the R rating of fiberglas. as moisture gets into the wall cavity thru many, many, access points. It's actual R rating decreases..
Celluliose suffers from the same problem. Get celluliose wet and it's R rating decreases.
Sprayed foam on the other hand isn't affected by moisture.. In fact it can be a moisture barrier..
Perfect insulation is near impossible with any sort of insulation (including foam) I have never seen a foamed house or any other insulated home perfectly insulated.. there always seems to be gaps or voids someplace.. I spend my day visiting new homes for a living..
Sprayed foam will cost around 20% more here in Minnesota where competition is forcing installers to be more competitive however you will more than make up the differance in cost when you factor in your furnace bills. rumor has it the price of heating isn't going to get cheaper in the future. It would seem like poor economics to save a thousand dollars now only to spend more than that extra for a single heating season..
Your costs may vary, objects in the mrror are closer than they appear, close cover before striking.. ;-)
Frenchy,Open cell SF is affected by water, closed cell not so much.
Convective current in wall cavity is as stated...warm air reaches outside wall cools and falls...Garett
Grott,
I've heard several people speak of open cell foam, I'm not sure what that is.. I know that if I spray a ball of foam and submerge it underwater I can leave it there for an exceedingly long period of time, cut it open and find the water hasn't penetrated into the foam.
Yes, you are correct, I misstated the warm air rises cold air settles thing in wall cavities. When my Dyslexia is bad I spend too much time trying to get the spelling somewhat reasonable and not enough time rereading for content..
Depending on the climate you live in, I would recommend using foam only on the ceiling/roof. About 85% of your heat loss goes out the ceiling compared with @ 15% thru the walls. It's still not cost effective if you aren't going to live there around 7 years. There are a few senarios were the payback term is less, but an average return is about 7 years.
When you do the calcs, the biggest heat losses are air infiltration/leakage, glazing and heat losses through any wood that connects the inside to the outside (i.e. "thermal bridging"). Depending on your design and construction methods, the largest loss may be infiltration or glazing, but it will be either one or the other. But these calcs rely on the R values tabulated for the insulation: if the R value of the insulation decreases with temperature, the insulated portion of walls and ceilings can become significant heat loss factors.
Window selection gives you a steep increase in cost for additional performance beyond a certain point. Warm-edge dual pane thermal units with low emissivity coatings and argon fill are pretty much the limit of the average person's pocketbook (and of eventual payback in energy savings- unless fuel costs increase a huge amount): additional thermal performance comes at staggering cost. Put these units in the lowest leakage window design you can.
Infiltration can be dealt with by a large number of means, but they fall into two categories: craftsmanship during contruction, or a method inherently lower in leakage. The former encompasses methods like careful gasketing, airtight drywall or extremely carefully detailed installation of air and vapour barriers etc. plus something else done in the rim/band joist space where doing a proper VB is damned near impossible. The latter is something like densepack cellulose or spray foam insulation- a method that forgives many sins in construction BUT NOT ALL! You can still have a leaky house even with spray foam insulation if you do other details wrong- but it's a lot tougher.
Dense-packed cellulose probably offers the best bang for the buck, provided you can find someone in your area who can do this properly.
Sprayed foam insulation is costly but gives superior performance. It is not without problems, though, and payback in terms of heating/cooling savings is on the order of years. If the installation method also eliminates thermal bridging, payback can be quicker. Of course, payback will improve rapidly if energy prices keep going up.
If you go with batts to save up-front money, use mineral fibre (Roxul etc.): the product is denser and hence represents less air movement within the batts as temperature drops. Then spend some of the money you saved by having the rim/band joist space sprayed with closed cell foam, which acts both as a VB and as insulation/air infiltration barrier.
Don't forget other major losers: canned lights in top-floor ceilings, bathroom fan and dryer and range hood vents with lousy flapper dampers etc. No sense in making your house "tight" if you let air p*ss out of huge holes that you deliberately cut through the airtight barrier! And if you go for tight contruction, you need heat recovery ventilation as well.
molt, another nice post.
People talk about the problem with FG in walls do to convection currents migrating throught the FG. I can see this in theory or if you just have a FG mat open at the bottom and open at the top. But if you have the FG in a stub bay, and you have a top plate with out electircal holes, and soleplates, and vapor barrier on the drywall side, and a nice shealthing job; migration would be very limitied. So your point about care in construction seems to be dead on.
Thanks, but I don't know for sure that I agree with your assessment in regard to the free convection losses within a batt-insulated assembly. I can see a free convection cell setting up, with air cooling and sinking along the sheathing and rising and heating along the drywall/VB. That's a free convection cell that would occur within the air of the batt itself. The higher the density of the batt product, the lower the rate of this free convection cell should be. Obviously if there is an air gap between the batt and the sheathing, the convection cell will be even worse.
Free convection losses is a problem with double glazed windows. If the gap between the panes of glass is less than 1/4" (I think) then there is not enough air in the gap to provide a sufficient insulator.
Conversely if the gap is greater than say 1/2" then you get convection loops inside the window reducing it's overall performance.
Hence the development of triple glaxed windows.
molten, thanks! I was thinking that when you (people) talked about convection you were saying that air moved in through small openings near the bottom of a bay and then passed out of the bay at the top. Now I see that you are saying air on the inside wall side is warm and travels up the wall and air on the outside falls, thus creating a loop of moving air which constantly takes heated air and moves it to the cool side of the wall. Thus wasting the heat. I see! Cool.
Don't know the difference in price but wish I did it instead of batts. Just the lack of worry over moisture intrusion & entrapment of moisture would be a welcome relief.
Mold, and certainly the integrity in the gaps would be worth it.
I've read over most of the responses, and as a homeowner, you're concerned about the complete package for yourself while you expect to live in this home. Total cost to build, cost to maintain. There is nothing wrong with batt insulation, there is nothing wrong with foam insulation. I've never heard of structural foam insulation, so it does nothing to add to the structural integrity of the home, that's just a marketing line. If a home is insulated properly, and your HVAC is designed properly, you should live very comfortly. Use higher density batts if you choose batts for the walls. Insulate the perimeter ceiling joist cavity space at least 2' in from the outside edge. Insulate more that R38 in the attic. Get a high efficiency furnace. Provide the proper amount of return air. Don't skimp on the quality of the trades doing the work.
>> I've never heard of structural foam insulation, so it does nothing to
>> add to the structural integrity of the home, that's just a marketing
>> line.I'm sure you've heard of Structural Insulated Panels (SIPs)? Do you think if you put FG batts between the two sheets of OSB, that you'd get the same structural characteristics as with foam? That's what Jer meant in post 80566.2
I don't believe the question was posed as cost in using SIP vs batt insulation. I understood it as spraying in foam insulation (iscenyne) between your studs and ceiling joists vs batts between your studs and ceiling joists. So, what is the thickness of your SIP composite to get your R=21 which you can get with a Knauf HD batt insulation in a 2x6 stud wall?
>> I don't believe the question was posed as cost in using SIP vs batt
>> insulation. I understood it as spraying in foam insulation (iscenyne)
>> between your studs and ceiling joists vs batts between your studs and
>> ceiling joists. So, what is the thickness of your SIP composite to get
>> your R=21 which you can get with a Knauf HD batt insulation in a 2x6
>> stud wall?I was responding to your statement that "structural foam insulation" is a marketing line. Clearly it is NOT just a marketing line, the foam being an important part of the structural integrity of a SIP (as well as providing the insulation).
>It's about a third to half again as much. The advantages are that you don't do the insulating, it gives a higher R-value for the amount of space, and it actually adds structral integrity to the house. For that last reason alone it's especially good for older under framed homes.<
Once again, no one is talking about SIP. My reference to the foam not adding to the structural integrity was in the context of the early point of this discussion. Existing walls, older homes, 2x6s. Anyone that wants to sell a guy foam insulation to help with the structural integrity of an existing wall, I'm sure I can find you an air hook to assist in the structural integrity of supporting a roof with no columns or bearing lines.
Joe,"There is nothing wrong with batt insulation," ...unless you are buying it based on its stated R value. If your purchase is strictly to meet code requirement then your fine.I purchase and install insulation of all types to increase the comfort and efficiently of a building. Dollar for dollar FG batts and blow-in are the biggest waste of money I see. The shame is all the $ in advertising the FG manufacturers spend to "sell" their product to the public, sales people and builders and evidently whoever taught you that there is nothing wrong with batts.Respectfully- stubbornly,
Garett
OK. I have nothing against foam insulation, however, foam insulation does not make it easy for you to do new wiring in Chicago, as everything has to be in conduit, so you'd wind up carving out the foam to run conduit and then you have to add insulation to fill the overcarved area. Installing batts is not rocket science, you just need to have your quality control.
We don't do any insulating until the trades have had, and passed al the nessary inspections. Any additional work will be more difficult but we are typicaly the last step before wall and ceiling finishes. No adding wiring after that! Garett
I guess it really a bite to do any work years down the line if one needed to.
FG insulation is a waste of money (it's just a poor air filter). A lot of folks always ask how much does Spray foam cost? It all depends on what density foam you want. There are 1/2 pound foams and 2 pound foams (2 pound is more expensive). What R value are you looking for. Do you require a vapor barrier? Is the area to be sprayed require scaffolds or can it be sprayed from a 2 step ladder? Lot's of factors effect the cost of a job.
If you consider that you can reduce the size of your HVAC equipment and energy savings can approach or even surpass 50%, does that extra few grand really matter since you can easily save that in the size of the furnace and AC unit you would require. I suggest you visit http://www.sealection500.com for more information. Personally I would never use FG insulation in any house I 'm involved in simply because I take pride in my work and believe that a spray foamed house adds value people are willing to pay for and it's good for the environment. Less energy to heat or cool your house is a good thing.
Regards...Whatnow...
P.S. If conventional insulation is so good (i.e FG) why don't they use it to insulate your refrigirator or freezer?
Because the the FG insulation industry doesn't need as good of a salesman as you.