Spray foam efficiency, looking for real world numbers. Foamed home owners in here->
I’ve been a reader of GBA for a year or so and learned quite a bit, thanks for providing a place to exchange thoughts!! My question is about spray foamed homes, I’ve read almost every post about it and we all know it will result in a smaller A/C and better efficiency, but what are the real world numbers? If you have a home that has been spray foamed and live in climate zones 1-3 please post some data!
How big is your home, 1 or 2 story, is the whole house spray foamed, a/c tons, a/c in conditioned area, climate zone, type of roofing/siding and most importantly what is your highest monthly kWh amount during the winter and summer? Please be specific (ACH50? Flash and batt? OVE? Exterior foam? HERS score? Peak internal & external temps?) so everyone can compare apples to apples. Don’t forget a/c tonnage and SEER. I’m trying to get a consensus on the performance of actual installations under certain conditions. Any help you can provide would be appreciated!
Chris B
Please remember to post energy usage (kWh) numbers, with conditions and season! It’s impossible to get an idea of the impact on efficiency without this. For those that are submetered, a/c and heater energy consumption numbers would be great!!
Also, not interested in alternatives to foam. This is to be a post to specifically answer people’s questions about energy usage in spray foamed homes under given conditions.
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I built a +/-4800 SF house in CZ 3 that was insulated with Icynene on all exterior walls and roofline and had an unfinished insulated basement. I don't recall the blower door test results, but the house had a HERS index of 48 without any renewable energy, with tankless water heaters, 90% furnaces and 14 SEER AC units. That said, reaching an equivalent level of performance could be reached with almost any insulation, provided the house is designed properly (window orientation and shading, locating HVAC in conditioned space, eliminating thermal bypasses, etc), and very careful air sealing and proper installation of the insulation. Spray foam does a good job, but it is not the only solution to high performance homes. Passivehouse projects often don't use spray foam, and many of the projects and professionals featured on this site use cellulose or blown fiberglass with great success. It's important to recognize that high performance building is all about process, products are secondary.
Great answer, Carl. As with any insulation, blower door testing is critical to effective application. The foam industry sells itself as providing both thermal & air barriers. But those of us that test know that even when properly mixed and conscientously applied, pathways still exist that can only be located and cured through testing.
Excellent response Carl!
I couldn't have said it any better.
I built a 5000 SF house in CZ 5a, ICF upper and lower levels, spray in roof topped with cellulose to get r 65. HERS 48, ACH@50 1.12. No renewables, condensing boiler. Hers was impacted by window choices, appliances and lighting (estar lighting was less than 30 percent). Also whole home electronics is an energy hog. Will skip the spray next time.
Recently did an energy retrofit of 70's built home with cantilevered 2nd floor (good design choice--not). Test in was 7.34 ACH50, Test out was 3.17 ACH50. Achieved with 3 layers of foam on the cantilevers (vertical and horizantal), caulking all plates in attic, removed whole house fan, boxed in can lights, topped the existing 5.5 inches (and that's being generous) of cellulose with 12 more.
Spring build will be double wall with cellulose (thanks to the great discussions on GBA), 4" exterior foam on foundation walls, r-60 attic, ADA.
Cool, a Not-So-Foamy award. Thank you, JB. (Still using--but less, awareness is the first step).
Carl, great post bro.
I will be doing my best to share this mantra, "It's important to recognize that high performance building is all about process, products are secondary."
I agree, great post Carl. Thanks for being specific, what about energy numbers? Please remember, the question was not about "alternatives to foam" or "the process", these are things that most of us are well aware of and can find answers to on this site. But what is not as readily available are real examples of energy usage with spray foam installs. There will be some great jobs and some not so great, this will yield an average performance, given the specifics of the home, that people can expect.
Chris Byers
Who is "we"?
and better efficiency compared to "what"
compared to a home with no attention to airtightness?
I can't help but notice that the 2 GBA Advisors who are Builders have decided to move away from sprayfoam.
Have the problems that I have read about air quality and out gassing been solved and documented?
Are there any environmental issues that need to be addressed with documentation?
AJ, thank you for your post and understanding the intention of the thread!
Lucas,
I'm not sure if you are posting quoted text as a question and answer but if you were I was looking for energy numbers (kwh), a HERS score is not energy, and if you were not please explain.
John, The intent of the thread is to get facts surrounding foam use. If you have the facts, share away John.
I wish I had utility bills for the two places I spray foamed. I am headed over to check on them next, and may find that the furnaces have not even turned on since the sun came over the mountain to shine on them today.
My two units outperform everything built around my parts. I have never had a build prior to these two where deep in the winter, that they could maintain indoor heat set points all day long with not one run of the furnace.
Yes, I need to document what I am posting but, at this time, I have not done so.
John, Many of us are headed to less foam use. But, I too want this thread to fill up with some facts and figures to do with foam use, not be a debate about whether to use foam unless truly just a side note like some of us are making it. Not a federal case.
Chris, this is a great thread and I hope it can stay somewhat close to on topic for all of us to learn from it. Thanks for posting it.
Update, my homes with Icynene are performing wonderfully.I was there for two hours after sunset before a furnace kicked on. Some of this is to do with good passive solar design. We put much effort into the entire design, with Icynene being just one part.