Assuming we are using Option 2 - Prescriptive compliance Path, the roof skylight of our project would need to abide with the U-value and SHGC listed on Table 5.5-3 (zone 3) of ASHRAE standard 90.1 -2007 SI (i.e. international version)

In our case, ASHRAE requires the U-value to be 3.92 and the Solar Heat Gain Coefficient (SHGC) to be 0.19.

It seems to me that this SHGC coefficient is extremely low and quasi- impossible to find on a market without paying a fortune.

Does the USGBC expect us really to install a roof skylight with a SHGC of 0.19? Isn’t there some kind of error? Perhaps there is a conversion to be made?

I would appreciate some help on this.

Many thanks,