Forum discussion
CS-2009 EAp2: Minimum Energy Performance
Hi,
I have calculated the U-Value of a Slab on Grade Floor to be 0.12 (metric) using 100mm insulation. The Leed reviewer wants to see the F-Factor equivalent in agreement with ASHRAE 90.1 2007 Table A6.3 however the min horizontal insulation is 300mm (within this table) and it does not quote R values above R-2.6. Therefore there is no real direct match from this table that I can pick. What would be the best way to respond in this case. Will a calculated U-Value not suffice ?
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Guillaume Martel
Architect PartnerProvencher Roy Architectes
2 thumbs up
August 18, 2016 - 5:17 pm
ASHRAE doesn't really allow other calculation methods for F-Factors.
Since your 100mm thick insulation would adequate +/-Rsi-3.5, I suggest you use the F-Factor of Rsi 2.6 as there's not a major change in value for unheated slabs.
What's the width of your insulation?
Also, have a look at Figure 5-K in the 90.1 User's Manual to see if you have others options depending on your project specifics.
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5907 thumbs up
August 19, 2016 - 11:56 am
You can extrapolate from the tables or provide a similar calculation to the method used in the table.
LEED does allow other than F-factor calculations because some of the modeling software does not model F-factor.