Bonus Room Over a Garage: Title 24 Requirements
A bonus room over a garage is an addition, and its floor is part of its envelope: a raised floor between conditioned and unconditioned space takes R-19 or U-0.037 in every climate zone. The floor, the rim joist and the duct route are the three items that set it apart from an ordinary room addition.
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Floor first
Whether you frame a new second story or finish a room that was built as unconditioned space, the garage ceiling becomes a raised floor separating conditioned from unconditioned space. Section 150.0(d) and Table 9-4 ask for R-19 in a wood-framed floor, or an assembly U-factor of 0.037, whatever the size of the addition.
Quality Insulation Installation applies only above 700 square feet. Where it does, the floor-over-garage protocol requires batts in contact with the subfloor, not doubled over or compressed, cut around wiring and plumbing, with every rim and band joist next to conditioned space airtight and insulated. At 700 square feet or less it does not apply.
Ducts and equipment
Ducts run through the garage are in unconditioned space, so extended ducts take R-8 in zones 1, 2, 4 and 8 to 16 or R-6 in zones 3 and 5 to 7, and the combined system is tested at 10 percent leakage or 7 percent to outside. Separately, Section 150.2(b)1D ii c asks that new or replacement ducts, air handlers, coils or plenums located in a garage space leak 6 percent or less, or have every accessible leak there sealed and smoke-tested by an ECC-Rater, whatever the duct length. It sits inside the part of Section 150.2(b)1D that Exception 4 to Section 150.2(a) applies to extended ducts, so plan for it. A ductless unit avoids the question.
What stays the same below
The garage remains unconditioned, so its lighting rules continue, including at least one luminaire on an occupancy or vacancy sensor. An addition of 1,000 square feet or less that is not a new dwelling unit skips the whole-dwelling ventilation airflow. If the room becomes an ADU, see ADU over a garage.
Size bands are on room additions, the framing case is on second-story additions, and the installation rules are on quality insulation installation. A vaulted version is attic conversion to living space. See our residential reports.
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
If you add heating or cooling to space that was unconditioned, yes. It is newly conditioned space, which Section 100.1 says must meet the addition requirements.
They are the same surface. The floor of the room is the separation between conditioned and unconditioned space, and it takes R-19 or U-0.037.
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