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Meeting U-Factor with Locally Built Windows

DL3SdBioAp | Posted in Building Code Questions on

Does anyone have any experience with demonstrating compliance with the IECC for locally (shop) built glass doors and windows? Climate zone 5A, so the U-Factor is 0.35. I hesitate to say ‘site built’ because these would be shop fabricated. We would be matching details to existing doors and windows that are about 150 years old. Haven’t been satisfied yet with commercially available options. Shop built is something we’re exploring, but meeting energy efficiency requirements is the first hurdle.

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  1. gusfhb | | #1

    As with all things the local code official is the ultimate authority. Were I trying to do such a thing I would probably over spec the glass, talk to the factory I was buying the glass from about what labeling can be put on the glass relating to U factor,then talk to the inspector with these facts and see what he or she says. A reasonable person would see a COG U factor of say .20 and figure you would have a hard time messing that up. An unreasonable person.................

  2. DL3SdBioAp | | #2

    Thanks Keith, that's probably the most logical approach. Short of testing, I was curious if the heat transfer rate could be calculated.

  3. gusfhb | | #3

    I have seen the process for doing this somewhere on the web, basically definitions of 'edge of glass' and 'center of glass'. If it is a wood frame, then R value of the wood etc. I imagine it would be a pretty good estimate. I believe window companies use a pretty large window size to rate with, making it look better than a normal size window would.

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