[Equest-users] Modifying existing historic windows

[Morteza Kasmai via Equest-users]

Dear all,

I am modeling a historic building and the scope of work is to modify the
existing windows by adding a storm window to the existing industrial steel
sash windows. The storm window is one layer Low-E glass with aluminum
framing with brake (assembly U-0.67).
Assuming the existing one layer clear glass window has U-value of 5.8, can
I assume the assembly R-value of the window system as the total R-values of
both of the windows as following, and would it be acceptable by the LEED
reviewer?

Total R-Value: 1/5.8 + 1/0.67 = 0.172 + 1.49 = 1.662
U-Value = 1/1.662 = 0.6

I would appreciate your help in this matter,
Morteza
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