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NC-v4 EAc2:Optimize energy performance

Uvalue for Slab on grade floor and ASHRAE 90.1.2010

Hello,

I am trying to  build my proposed and my baseline building in equest.

My problem is that for the structure element " floor on slab" I need to Input the Uvalue.

In ASHRAE 90.1.2010 in table 5.5.3 for this structure element the F- factor is given in Βtu/(h ft F).

Do you know the relation between the Uvalue and F-factor? 

Thank you very much

 

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Paula Melton
Editorial Director
BuildingGreen, Inc.
LEEDuser Expert
159 thumbs up

Tue, 11/06/2018 - 17:08

Hi, Konstantina! Wondering if this thread might help: https://leeduser.buildinggreen.com/forum/u-value-f-factor
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Marcus Sheffer
LEED Fellow
7group / Energy Opportunities
LEEDuser Expert
4454 thumbs up

Tue, 11/06/2018 - 17:25

Slabs are usually insulated around the edge, both in under the slab and down along the outside. The F-factor accounts for the edge treatment since this is where most of the heat loss occurs. Think of it like a whole assembly U-value of sorts. Some software like eQUEST uses this value. A U-value can be used in software where the F-factor is not used. Just apply the U-value to the correct areas of the slab. So there is no direct relationship where you can convert one to the other. The F-factor can be derived from 90.1-2010 Appendix A - see Section A6 and Table A6.3 for additional guidance.

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