The baseline U-values proposed by ASHRAE 90.1-2007 for a building with high thermal mass in climate zone 1 (see below extracted from table 5.5-1) seem to be too low-performing. Are these correct? If so, why are they that low-performing? Is it to do with insulation not being usually specified in hot dry zones?
- Roof (Insulation entirely above deck) = 0.063BTU/hr Ft2F = 0.3577W/m2K
- Walls, Above-Grade (Mass) = 0.580BTU/hr Ft2F = 3.2934W/m2K
- Floors (Mass) = 0.322BTU/hrFt2F = 1.8284W/m2K
- Fenestration (All) = 1.200BTU/hrFt2F = 6.8139 W/m2K
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5906 thumbs up
April 13, 2012 - 9:28 am
Those are the baseline prescriptive values. Do not use the mass values for your appendix G model (see Table G3.1#5(Baseline)(c).
In the US this climate zone requires little to no heating, a lot of cooling and tends to have frequent high humidity. Definitely not dry.
The ASHRAE 90.1 committee would need to answer why they are what they are. Uninsulated mass buildings with single pane windows are pretty standard practice in those areas of the US.
Ameet AA
41 thumbs up
April 27, 2012 - 7:33 am
Thank you Marcus! Project location is in middle east and no heating require.so if we considered these values as the basline then the compared saving with proposed building would be massive.