Two short questions about modeling the envelope: 1. For my proposed model, am I required to follow the tables from appendix A even when my project is outside the US? In Peru, our reality is that there is no insulation for envelope elements of buildings; so what would be my input data for tables A? 2. For my baseline model, is it ok if I model just one layer as long as it fits the U-value in the table 5.5-X? Thanks in advance.

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Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

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Mon, 11/25/2013 - 17:03

1. The table in Appendix A cover uninsulated assemblies. The whole idea is to account for the whole assembly U-value including the framing. The same values apply outside the US. 2. In the Baseline you can just model the U-value if your software allows you to do so without entering layers.

Ron Dean

Sumac Inc.

LEEDuser Basic Member

20 thumbs up

Mon, 11/25/2013 - 21:19

At the top of table A3.1A (for masonry walls), for R-insulation, there are three options: * Assembly U-factors for 8 in. Normal Weight 145 lb/ft3 Solid Concrete Walls * Assembly U-factors for 8 in. Medium Weight 115 lb/ft3 Solid Concrete Block Walls * Assembly U-factors for 8 in. Medium Weight 115 lb/ft3 Solid Concrete Block Walls: Partially Grouted So, my question is: what if I have masonry walls covered with concrete that in total is 9.8 in. ? Please advice.

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Mon, 11/25/2013 - 21:28

Extrapolate or conservatively use the lower value produced by the 8 inch masonry or look up the R-value of 1.8 inches of concrete and add it to your Appendix A total or if the wall is just solid concrete just use a point calculation. The difference in any case should be very minimal. Appendix A is intended to account for framing effects, especially steel conduction, in whole construction assemblies.

Ron Dean

Sumac Inc.

LEEDuser Basic Member

20 thumbs up

Mon, 11/25/2013 - 22:50

Thanks Marcus, I think a good idea may be to get the R-values for the bricks and then add the R-value of the concrete at both sides. I mean, get the U-value by calculus instead of tables A.

Marcus Sheffer

LEED Fellow

7group / Energy Opportunities

LEEDuser Expert

4454 thumbs up

Tue, 11/26/2013 - 00:21

If you don't use Appendix A make sure to explain to the reviewer how you derived the U-values modeled. Appendix A is a readily accepted methodology. Your calculus would potentially require additional justification.

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