Sustainability Energy Code 2020: Building Envelope

This post is our second of the series covering updates to the upcoming Energy Code, effective 2020. In the previous post we covered how these updates will affect Mechanical systems (see link). In this article we are focusing on what will affect the Building Envelope, including the walls, roof, floor and all openings.

Although the changes are subtle and don’t affect the way a home might look. These code provisions will significantly improve building performance during the life cycle and also increase coordination efforts during design and construction. Which is why they should be reviewed prior to any design and construction as to avoid unforeseen issues during construction.

Building Envelope Updates

  • Wall assembly: HERs Verification for Walls
    • If you have worked on a project needing to comply with T-24 Energy Requirements, you have coordinated HERS testing verification for ducted air systems. Now HERS verification will be required to test Building Enclosure for Air Leakage and to verify the Quality of Insulation Installation.
    • Air Infiltration is one of the main causes of performance loss, this occurs when conditioned air (hot or cold) leaves the interior of the space and escapes to the exterior. Testing will check appropriate caulking, sealants, gasketing and weather stripping to ensure optimal building envelope. See this link the resources below for more information on Air Infiltration causes.
  • Roof assembly: Insulation
    • Insulation at or above roof deck is no longer allowed, this was Option A per Table 150.1a-b of the Energy Code
    • Roof and ceiling insulation must meet Options B or C per Table 150.1a-b of the Energy Code. Option B which requires insulation at the ceiling and roof rafters and Option C. In short, this is adding the amount of insulation that it will take to properly condition a space. Type and quality of insulation will be left up to the builder as long as it meets the appropriate R-value.
Photo by Steve Johnson on
  • Windows and Doors
    • Doors with 25% or more glazing are now considered “Fenestration”. This means, that glazing within doors will then have to comply with performance standards for Window glazing, such as SHGC and U-Values.
    • When buying a glass door at your local Hardware Store, we might only look at the design, color, material etc. With this new code, you will have to look at a more important option, does the glass meet my energy performance, will it have to be dual-pane, tinted, meet Solar Heat Gain Coeffient and U-values. In short, yes!! Your doors will have to meet all these requirement.
  • Additions and Conversions… Maybe ADU’s
    • Walls that are extended for an addition must meet prescriptive insulation requirements. These depend on the size of wood framing being extended, R-15 required for 2×4 and R-21 required for 2×6.
    • This applies to additions that are using existing walls when converting a non-conditioned space to a conditioned one. I see this specifically being relevant to ADU garage conversions, where one might attempt to preserve as much of the existing structure as possible. See this link for more information on ADU’s.
Image from

In Conclusion

The summary of these Energy updates by  no means is inclusive of all information necessary to understand what it takes to build an energy efficient home in 2020. But it does give you an idea of how the updates might impact your project.

Given that we now have more clear prescriptive requirements for alterations and conversions of non-conditioned single family spaces, it gives the impression that California might be preparing for a surge in Accessory Dwelling Unit construction and potential densification of our neighborhoods. The energy might be falling in line with newer forms of small-scale development.


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