REScheck Compliance Certificate
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| Posted in Energy Efficiency and Durability on
I used Demilec spray foam for a house I am building in Charlotte NC and we sprayed 5″ to 6″ in the rafters. When I asked about the issue of how many inches and why we wouldn’t do more they referenced a Rescheck Compliance Cert.(sent me a copy) and said 5 to 6″ was equal to about 22 to 24 rvalue. The house passed inspection at this 5 to 6″. I hear 2 different sides and not sure who is right.
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If you have a few hours to read thru 300 posts....
https://www.greenbuildingadvisor.com/blogs/dept/musings/it-s-ok-skimp-insulation-icynene-says
I will save you some time
The spray foam-ists are wrong and Martin is right
We should build homes with air barriers AND at the very least Meet the Minimum code values for R-value...
Better yet we should be doubling Minimum Code R-value
Chris,
Demilec makes several kinds of spray foam insulation. Each product has a different R-value per inch.
For example, Demilec Heatlock Soy is rated at R-6.9 per inch. Demilec Sealection 500 is rated at R-3.8 per inch.
What type of insulation do you have?
Chris,
Assuming that the type of insulation used was Demilec Sealection 500, you have between R-19 and R-22.8 in your attic. You'll have to check your local building code requirements to determine whether that amount is code-compliant.
AJ,
You wrote, "The huge advantage to spray foam is that it has a high effective insulation value due to the fact that air is not moving through it." However, the way most scientists (and the U.S. government, in the Federal R-Value Rule) define "insulation value" is with the R-value scale. Assuming we are talking about R-value rather than the building's air leakage rate, then R-19 is R-19, no matter which insulation you use.
Chris, your home is compliant via the paperwork sent to you. The huge advantage to spray foam is that it has a high effective insulation value due to the fact that air is not moving through it.
There are those that poo poo it including me for various reasons. I personally am mainly concerned with having a contract that has the applicator on the hook for correcting a bad spray. Very important to verify that who you hire knows what he is doing and is working in the right conditions with his best men and best equipment in top working order. Also people with any breathing sensitivities and spraying homes that are occupied concerns me greatly.
That said the amount of insulation you have is fine. More is better but a superinsulated home needs to be designed in full not just spraying more thickness in one location.
Your HVAC bills will confirm my post Chris.
AJ,
If the REScheck report was used as part of the performance path of code compliance, of course it's possible to achieve code compliance with a lower R-value than necessary for those following the prescriptive path.
I'm glad that your multiplication method is the same as mine. We both arrived at the same figure for 6 inches.
Martin, Chris has a Rescheck compliance certificate. The same idea is used by my spray company. His bills will prove the worth of his highly airtight insulation. I have two homes with sprayfoam done very similar and am not armchair posting Martin. These two homes use way less energy than any non sprayfoam build I deal with. Some day soon I may be involved in a passive house project and that day will most likely be the first time I see better results.
And your math is leaning toward the low side Martin. 3.8x6=22.8. And in any event you of all people know the value of sprayfoam. Lack of issues with the movement of AIR which as you very well know is, a very very good characteristic of, sprayfoam.
We are not helping someone decide on a future build. This is a done deal and will perform well.
Martin, you know sprayfoam works well and I know it.
Off to install a new well and water system.
;)
Yes it is the selection 500.
Martin what do you mean by prescriptive path?
Chris,
The prescriptive path of a building code lists minimum R-values and glazing specifications. The performance path, on the other hand, requires the use of a software program to prove that using components that would not meet the minimum prescriptive requirements still result in a building that uses about the same amount of energy as a building that follows the prescriptive path.
For example, if a builder wanted to skimp on attic insulation, but wanted to add more insulation to the walls, the resulting building might use the same amount of energy as a building meeting the prescriptive code.
For more information, see Are Energy Codes Working?
Who is right? What you have is way better than fiberglass batts. More than 6"s of sprayfoam is of course more insulation and an advantage. Why it isn't done is the cost. When it is done, a choice is made to pay more.
It is that simple Chris. What you have is quite good especially if you heat with natural gas and or have spent extra for a ground source heat pump system.
Proper windows and shade trees and overhangs and winter southern exposures also are beneficial if designed and built well.
AJ,
Your above posts are EXACTLY why you have pissed off so many individuals on this website. It is obvious you are trying to provoke Martin into an argument... and about what? Spray foam?
We all know spray foam can perform well. We also know that more cost effective (and MUCH more green) strategies can be used to achieve the same performance level. Blown-in cellulose and exterior/interior air sealing can be just as effective.
Now if there is a cavity size restriction (ie a 2x6 roof rafter) then perhaps closed cell spray foam is an appropriate strategy because of the higher R value per inch.
But your posts say nothing in regards to the appropriateness of spray foam in compact wall/roof cavities... Nope, just that spray foam is good and everyone should use it.
and then.... and then... you suggest ground source heat pumps! Have you ever conducted a cost/benefit analysis on these systems??
You are trying to exert yourself as an expert on this website. But you really should do your homework.
At the risk of making this discussion even more personal...
I disagree with Brett about AJ's motives. AJ is expressing his confidence in the insulating value of foam, even when installed to below code minimum R-value. There is general agreement here on a few things: one, air-tightness helps make insulation effective. Air sealing all sides of a cellulose insulated stud bay is one solution, and spray foam is another. Second, R-38 beats R-19, and R-76 beats R-38. If all you get is R-19 foam, at least it should insulate better than an R-19 fiberglass batt. However, this is still a half-ass job, and meeting code minimum would be a good benchmark even if the inspector will approve the half-ass job. And for anyone committed to going beyond half-ass, there are ways to get there without spray foam.
This is the Green-Building-Advisor not the Just-Barely-Meets-Code-Advisor
Hard to say who "AJ Builder" is trying to provoke this time.
I really doubt that he is a builder.
I agree with GBA Advisor Michael Chandler
I think the most of Martin and post so always. I am not for GSHPs pumps where I live with 43 degree ground water. Carolina is a different climate and they will perform well there. If one wants to spend more for foam or GSHPs, they will. None of my posts above recommended foam or GSHP. All I said was if chosen, they will reduce one's energy needs. This is very much true. I have used foam at the exact thickness as Chris 5 years ago. The two homes barely need there half sized HVAC SYSTEMS.
If you have direct experience Brett that is otherwise, post it. I am here to share and learn. Please stick to the stated policy above and avoid posting back and forth with me if you harbor uncontrollable emotions. ;)
John, Chris already has his sprayfoam in and paid for. He is asking about the paperwork. Martin and I addressed that. This thread is not about if cellulose is smarter. Many of us including myself know there are less expensive greener insulation strategies. It's just NOT the topic of this thread.
The idea is to get along on this site or move off it John. Peace.