While fully wanting to have the most thermal barrier I can have, should I believe Rem/Rate when it tells me that R-value does so little? By changing the R-value # only for the ceiling (roof) in Rem/Rate, the cost savings is ~$75/yr on my house specifically, and the load reduction and carbon reduction are also nominal.


There is the ongoing discussion about cheating the customers by only spraying R-21 in lieu of R-30 (our local R-value requirement). The diminishing returns after a complete air seal is met with spray foam seems to suggest there is no need for the extra costs. I don't think it is debatable whether or not the greater R-value # you have (thickness), the more thermal resistance you should have if it is installed properly. But should the insulation types be counted as equals? Should we make it so tough to put the ducts in the envelope?


As I understand it, R-value for code has been based on conductance only and not the 2 other types of transfer. By not giving spray foam credit for the air sealing qualities it potentially has seems to make the two types an unfair comparison.


The only thing I think must happen is the enforcement of code regarding air leakage testing of all spray foamed and air sealed houses with blower doors, new and retrofit. With all the homes that I have been testing, there is obviously a need for this service. So many of these installers have been looking at this like painting and not using building science in their approach. There are huge energy saving claims by many of these companies, and the housing stock and clients are not getting a good deal.


Those building envelope gaps are a plenty!! This past summer in the hot/humid environment of Hilton Head Island, SC, those newly spray foamed attics were hot/humid, and those ducts were dripping condensation like crazy! Small mistakes in spray foam seems to be the cause of lots of problems.


One big question that also needs to be addressed is, how do you know if the house is too tight and you need ventilation without testing? Not many around here are testing. Some of these retrofits have gas appliances and are in retirement communities. I see potential concerns for health and safety here.


Of course there is the article titled "It's OK to Skimp On Insulation, Icynene Says" by Green Building Advisor contributor Martin Holladay which clearly states his position. Although I agree that requirements are requirements and codes are codes, what should we do about the ROI and the information our energy modeling software tells us? If we make it too hard and don't give constructive guidance, how are we going to move forward?


What are some thoughts on this?

Tags: Blower door, Building Envelope, R-value, fiberglass insulation, spray foam insulation

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I have a product design that fits between studs that's two heat-transfer units tied with a thermal fluid, thanks for posting, I was wondering about floor-ceiling temp differentials.


The diagram shows about 13F, haven't checked yet but I think it's enough for the unit to be passive, fluid expansion is ~0.055%, works both ways, moving coolness up in summer or heat down in winter.


Pretty ready for production, OTS for parts in the assembly, working on standardizing, interested parties in mfg'ing these let me know.



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