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

[Nick Pine]

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

> The institution that rebates home energy improvements here in Oregon 
> is balking at paying out their $2.25/square foot rebate for storm 
> windows because they were not installed by a licensed contractor... 
> http://www.energytrust.org/residential/hes/windows.html Their rules 
> stipulate tiered rebates based on U-values around 0.3.

Their weatherization manual says:
"Replacement windows shall be certified and labeled for U-factor in 
accordance with the simulation, testing, and certification procedures of 
the National Fenestration Rating Council Incorporated (NFRC)."

That seems to be the legal criterion, but it leaves questions, eg who 
does the certification, and how is it "in accordance..."? :-) You might 
ask a contractor to certify that a window assembly (the old window plus 
an indoor and outdoor storm window?) is less than U0.30. Can a 
contractor "manufacture" a window by modifiying it in place?

> 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?

Two layers of plain glazing would be about U0.5. U0.3 would require 3 or 
more
layers, or low-E. You might somehow measure this and say it meets the 
intent of
the rebates, but that seems like a hard sell. They want to see an NFRC 
label or
packing slip from a window manufacturer.

Nick