[Greenbuilding] U-value of single pane plus wood-frame storm

[Nick Pine]

> Reuben Deumling <9watts at gmail.com> writes:

>> My question is if there is a simple , or inexpensive, way to assess 
>> U-value. Now that I acquired an infrared thermometer (Fluke 63) I'm 
>> able to measure the temperature drop across the two panes vs. the 
>> drop across the single pane window in the front door, but this is of 
>> course not the same as measuring U-value. Any ideas?

You might buy and install one NFRC-certified U0.3 window and measure the 
indoor glass temp. If it's 70 F indoors and 30 F outdoors in the shade, 
(70-30)1ft^2xU0.3 = 21 Btu/h would flow through the indoor pane, which 
would make it 70-21/1.5 = 56 F, with a slow-moving indoor airfilm with a 
1.5 Btu/h-F-ft^2 conductance. If the retrofit windows have equal or 
higher indoor glass temps at the same time, you could argue that they 
are U0.3 or less.

Nick