Home Addition With a Heat Pump Water Heater: Title 24 Guide
A second water heater in an addition can be a single heat pump unit with its tank indoors on an R-10 base and a communication port, or one that meets NEEA Tier 3. Additions of 500 square feet or less may use an electric heater with point-of-use piping instead. The heat pump unit then needs venting and sometimes backup heat.
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The four options
- One heat pump water heater with the tank not outdoors, on an incompressible rigid surface of at least R-10, with a communication interface that meets Section 110.12(a) or an ANSI/CTA-2045-B port.
- One heat pump water heater meeting NEEA Advanced Water Heater Specification Tier 3 or higher.
- For additions of 500 square feet or less, an electric heater with point-of-use distribution under RA4.4.5.
- A system the Executive Director determines uses no more energy.
The point-of-use appendix limits each hot water run to 15 feet of 3/8 inch pipe, 10 feet of 1/2 inch or 5 feet of 3/4 inch.
Where the closet becomes the problem
An integrated unit needs air. Section 110.3(c)7B gives four routes: the manufacturer's method, an open room of at least 100 cubic feet per kBtu/h of compressor capacity, permanent vent openings, or ducting. For a unit with 4 kBtu/h of compressor capacity that is 400 cubic feet. A closet 3 feet square with an 8-foot ceiling holds 72, so it takes the vented route: 225 square inches of net free area (125 plus 25 per kBtu/h) in fixed louvers, split between an upper and a lower opening or a fully louvered door, venting to a neighboring space that supplies the rest of the volume.
Cold inlet air
Where the inlet air is unconditioned, as in a garage or crawlspace, backup heat is required unless the compressor cut-off sits below the Heating Winter Median of Extremes for the closest listed location. A built-in resistance element counts. See heat pump water heater installation.
What it does not mean
Only the additional heater faces this list. If the existing heater is replaced too, that is an alteration with its own options under Section 150.2(b)1H, and if the old heater simply serves the new rooms, none of it applies: see existing water heater in an addition.
Related: water heater requirements, room additions and residential Title 24 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
Not under the first option. Section 150.2(a)1D says the storage tank shall not be located outdoors, and the unit sits on an R-10 rigid insulated surface.
Not prescriptively. The listed types are heat pump units and, up to 500 square feet, a point-of-use electric heater; other types need performance modeling.
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