[Equest-users] Effective Insulation/Farming Layer R-Value Value

[Daniel Knapp via Equest-users]

I would just pick the R-value for insulation (21, 25?) that best matches the R-value of 4 inches of polyurethane spray foam. The depth of the cavity doesn’t make much difference to the end result. If the R-value you’re aiming for isn’t 21, or 25, just interpolate using the numbers in the table. Note that small differences in the R-value don’t make much difference to the effective R-value as thermal bridging has such a strong effect. 

—
Daniel Knapp PhD, P Phys, LEED AP
danielk at arborus.ca

Energy Efficiency Expert
Arborus Consulting
2-43 Eccles Street
Ottawa ON K1R 6S3
(613) 234-7178

> On Jul 19, 2017, at 10:16 AM, Morteza Kasmai via Equest-users <equest-users at lists.onebuilding.org> wrote:
> 
> There is a wall section in this project with 4” thick interior polyurethane spray foam inside the metal studs.
> Since Table A9.2B of ASHRAE 90.1 does not provide the effective insulation/framing layer R-Value for this type of insulation, how can one calculate this value?
> 
> Your thoughts and suggestions would be highly appreciated,
> Morteza
> 
> 
> 
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