Window NFRC ratings and airtightness
I’ve read about NFRC rating. Intuitively, infiltration seems like it should be one of the more important considerations- if the window is leaking air, the U/R value seems secondary.
I’m looking at windows that are NFRC listed. However the NFRC listings on the website do not seem to include infiltration for many windows. You can navigate to the particular window via manufacturer and window type, and from there select the product line, which then brings you to a page with “General Information: and a ratings table.
The General Information includes a cell for Air Leakage, but for many windows, air leakage is blank. In the ratings table, there is a column for U-factor, SHGC, VT and Condensation Resistance. If I click on the CPD# link for the particular window, it brings up a pop up window with a table that includes a box for Air Infiltration, but that box is also blank.
It appears that to meet Energy Star, a window must have infiltration of less than 0.3.cfm/ft2. The manufacturer’s website has a page indicating Air Infiltration is 0.05 (cfm/ft2 of frame @ 1.57 psf wind pressure).
At first glance 0.05 seems good, but since it does not appear on the NFRC site, I’m suspicious of the number. Is there any good reason a window from a national manufacturer would not have it’s air infiltration rating on the NFRC site? Is the psf of 1.57 appropriate? What psf is associated with the Energy Star requirement of 0.3 cfm/ft2 assume?
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