[Equest-users] Exterior Air Film and U-Value Specification Methods

[Jonathan Smith]

eQuesters:

 

Because eQuest assigns the exterior air film R-Value as a function of
orientation and wind speed, what is the best practice for specifying the
baseline model exterior above grade wall U-Value? It is my assumption
that 90.1 baseline 5.5 Tables includes an R-Value of 0.17 for the
exterior U-Value (See Appendix A3.3.1-General). Can anyone else confirm
this assumption?

 

To make a correct comparison of U-Values between the proposed and
baseline, it would seem to me that this air film R-value should be
subtracted from the 5.5 Tables baseline U-Value specification when input
in eQuest. Otherwise, there would be a double counting of air film
R-Values in the baseline calculation. Does anyone have insight into the
USGBC perception of this calculation methodology? I assume that USGBC
might require proof that the R-Value does not fall below 0.17. 

 

Are there any prohibitions in 90.1 to simulating the baseline building
envelope without the thermal mass effects? For example, is it
permissible to specifying eQuest walls using the U-Value input in lieu
of the layers input? 

 

Jonathan R. Smith AIA LEED(r)AP

 

 

40 Beaver Street
Albany, New York 12207
p: 518.463.8068 x268
f: 518.463.8069 
www.csarchpc.com <http://www.csarchpc.com/> 

 

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