How Does a Heat Pump Change a Title 24 Calculation?
The reference house in the calculation has a heat pump. A heat pump at minimum efficiency scores even, while a gas furnace adds heating energy that the rest of the design must offset. Choosing a heat pump also brings controls and tests: supplementary-heat limits, a defrost timer and refrigerant charge verification.
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The baseline you are measured against
Table 150.1-A allows no electric resistance space heating in any zone and sets the heat pump at minimum HSPF2 and SEER2 in all 16. The compliance manual spells out the consequence: a proposed central gas furnace significantly increases heating source energy compared with that reference, and the gap shows up in the compliance margin. Prescriptively, heating must be a heat pump, so a furnace is only reachable through performance compliance.
Making up a furnace penalty
The deficit has to come from elsewhere in the design: better envelope, quality insulation installation, or a battery paired with solar, which can release a modest efficiency credit. A larger array alone cannot help, because solar does not affect the efficiency score. Credit for a variable-capacity heat pump must be field verified by an ECC-Rater, and so must the heating capacities at 47F and 17F when performance compliance requires a heat pump.
Supplementary heat limits
- Supplementary electric or gas heat must lock out above 35F outdoor temperature, and may run above that only during defrost or when the user selects emergency operation.
- Electric resistance capacity may not exceed 2.7 kW per ton of nominal cooling capacity at 95F, rounded up to the closest kW.
- Homes under 500 square feet, and homes of any size in zones 7 and 15, may use alternative controls.
Defrost and testing
If the unit has an installer-adjustable defrost delay timer it must be set to 90 minutes or more and certified on the CF2R. Zones 6 and 7 are excepted, as are homes of 500 square feet or less in zones 3, 5 through 10 and 15. Refrigerant charge verification applies to heat pumps in all 16 zones, so the ECC-Rater visit is not optional; duct testing is the companion visit.
For an existing home
A swap in an alteration is judged by the altered-component rules, covered in the replacement checklist. For the plain requirements read heat pump requirements, and for detached units whether an ADU can use a gas furnace. Our residential report models the combination for you.
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
Through the performance method, yes, if the rest of the design offsets the heating energy. The prescriptive package requires a heat pump.
Only if the higher rating is modeled and verified in the field by an ECC-Rater.
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