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Forum discussion

NC-2009 EAp2:Minimum Energy Performance

Determining R-values for LEED wall assembly

Todd Bundren

Associate Principal - Director of Sustainabilty

Lawrence Group

LEEDuser Premium Member

10 thumbs up

February 26, 2013

Is there a standard way the USGBC wants the R-value of a wall assembly to be calculated taking into account the framing factor or thermal bridging that occurs with metal studs? In addtion, I have provided a nominal 1/2" air gap between the exterior masonry wall and the metal studs to reduce the thermal bridging effect. Does anyone know of an approved methodology to determine the R-value of the wall for energy modeling purposes? Thanks!

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Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Tue, 02/26/2013 - 21:44

Appendix A in 90.1 is the approved methodology for de-rating the insulation values of building assemblies related to thermal bridging. Many projects simply enter the assembly layers into the modeling software which does not account for the thermal bridging. This is a very common mistake in LEED submissions.

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