Does Window Orientation Matter for Title 24 Compliance?
Yes, in two places: the 5 percent cap on west-facing glass in zones 2, 4 and 6 to 15, and every performance calculation, which uses the true compass direction of each window. Same-area replacement windows are not held to the area caps, but moving or adding glass can bring them into play.
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What counts as west-facing
Section 100.1 defines west-facing as within 45 degrees of true west, including north-west and excluding south-west. Skylights tilted in any direction count as west-facing when the pitch is under 1:12, under Section 150.1(c)3C.
The prescriptive cap
Table 150.1-A limits west-facing glass to 5 percent of conditioned floor area in zones 2, 4 and 6 to 15 and sets no limit in zones 1, 3, 5 and 16. The 5 percent sits inside the 20 percent total. In a 1,800 square foot home that is 90 square feet of west glass.
When it reaches an existing house
- Replacement in place: Section 150.2(b)1B points to the U-factor and SHGC sections, 150.1(c)3A and 150.1(c)4, not to the area limits, so a same-area swap faces no west-facing test.
- Added glass: Section 150.2(b)1A applies the limits, but up to 16 square feet of new fenestration is exempt from the total and west-facing area requirements.
- A window moved to another wall: the manual calls any moved component an alteration, and glass added to a wall beyond what was removed from it is new area.
In a performance calculation
The proposed home is entered with the actual azimuth of its front. For up to 20 percent glazing, the standard design places one quarter of the same total area on each of north, east, south and west, so moving glass off the west wall earns credit and adding it costs. The 2022 manual notes that low afternoon sun makes overhangs ineffective on east and west faces and advises minimizing glass there in cooling climates.
On the job
The installer records each window's orientation on the installation certificate. The manual calls changes to a window's location hard to judge, and a field change that causes noncompliance needs revised plans and compliance documents approved by the enforcement agency.
Sun-control options for south glass are on window overhangs. Glass caps for new rooms are on room addition Title 24, and zone values are on the climate zone page. Our residential reports model orientation.
Common Title 24 Questions
- When is Title 24 required for a home?
- Does a remodel need Title 24?
- Does a room addition need Title 24?
- What plans are needed for a residential Title 24 report?
- How much does a residential Title 24 report cost?
- How long does a residential Title 24 report take?
Frequently Asked Questions
Yes. West-facing and south-facing are defined from true compass directions, and the performance input is the actual azimuth of the front of the building.
It can in the performance method, where the standard design spreads glass evenly across the four directions. The manual advises minimizing east and west glass in cooling climates.
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