California code requirements vs. realities - May blog
For many years, California has been a leader in driving building energy code stringency, with its Title 24 energy requirements ahead of U.S. model codes. The current fenestration U-factor requirement for the entire state of California is more stringent than required by ASHRAE Standard 90.1-2016 for its climate zones (3-5) covering California. And performance certification by the National Fenestration Rating Council (NFRC) is required for both residential and non-residential fenestration, including site-built systems. But does that mean that an increase in performance of installed fenestration is actually occurring?
The current Title 24 prescriptive U-factor requirement for commercial fixed windows is 0.36 BTU/of.hr.ft2, which typically requires the use of a thermally broken aluminum frame and a dual pane low-E insulating glass unit with two of the following strategies: warm-edge spacer, wider thermal breaks, argon fill or fourth surface low-E coating. The proposal for the next revision of Title 24, which will become law January 1, 2023, includes a further reduction to 0.34 BTU/of.hr.ft2 for non-residential fixed windows. Achieving this performance will need two, probably three, of these strategies.
One would therefore expect fenestration with this level of performance to be widespread in Californian commercial buildings. However, that does not seem to be the case. According to many industry participants, the use of the fenestration strategies listed above remains limited: Thermal performance of aluminum framing remains at a basic level and highly conductive aluminum insulating glass edge spacer is ubiquitous. At a recent Title 24 stakeholder (virtual) meeting on non-residential envelope performance, participants appeared frustrated at how infrequently fenestration systems are used that meet even the current U-factor requirements.
After discussions with several participants in the California construction community, it appears that the reasons for the disconnect between stringent code requirements and the reality of installed fenestration are multiple...to continue reading click here.
(the full blog, as well as previous posts, are hosted on usglassmag.com)
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