CALGreen's HVAC sizing rule drops Manual J-2016 and Manual S-2014

Here's the thing: the rule that tells you how to size a home's heating and cooling system lives in two different parts of Title 24, and right now they don't agree. CALGreen says one thing. The California Energy Code says another. California is moving to end the argument — and the practical lesson lands on your desk today, not in 2027.

The rule that's changing

CALGreen Section 4.507.2 — "Heating and air-conditioning system design" — is the residential mandatory measure that makes systems be "sized, designed and have their equipment selected using the following methods." The 2025 text names manuals by year:

• Item 1: heat loss and heat gain per ANSI/ACCA Manual J-2016, ASHRAE handbooks, "or other equivalent design software or methods."
• Item 2: duct sizing per ANSI/ACCA Manual D-2016.
• Item 3: equipment selection per ANSI/ACCA Manual S-2014 "or other equivalent design software or methods."

Then it adds a short exception: "Use of alternate design temperatures necessary to ensure the systems function are acceptable."

That exception reads like a door. It isn't.

What the Energy Code already requires

Flip to Part 6, the California Energy Code, and the design conditions are nailed down. Section 150.0(h) fixes the indoor design temperatures at 68°F for heating and 75°F for cooling. It bounds the outdoor design temperatures: heating no lower than the 99.0 percent Heating Dry Bulb, cooling no greater than the 1.0 percent Cooling Dry Bulb. And for equipment, it requires sizing based on ACCA Manual S-2023 — with furnace heating capacity set by Manual S-2023, Table N2.5.

Verified against the live 2025 California Energy Code (with January 2026 Errata): §150.0(h)2 fixes 68°F/75°F indoor and the 99%/1% outdoor bounds; §150.0(h)5 ties sizing to ACCA Manual S-2023 and furnaces to Table N2.5.

These aren't voluntary. They're mandatory features in Part 6, in force now.

The exception was never a key

So picture a load calc that leans on CALGreen's "alternate design temperatures" exception, or cites Manual S-2014. On the CALGreen page, it reads compliant. Against 150.0(h), it doesn't — the indoor temperatures are fixed, the outdoor temperatures are bounded, and the equipment manual is the 2023 edition, not 2014.

That's the trap. The CALGreen exception never overrode the Energy Code. Part 6 set the design temperatures regardless of what Part 11 seemed to allow. Anyone padding design temperatures "to ensure the system functions" was already offside against 150.0(h) — the exception just made it look permitted.

What the 2027 supplement does

HCD's 01/25 final express terms clean up the conflict directly. In the express-terms language, 4.507.2 Item 1 is repointed to Energy Code sections 150.0(h)(1) and (2), and Item 3 is repointed to 150.0(h)(5). The "alternate design temperatures" exception is struck entirely. Manual D-2016 duct sizing stays. HCD's change matrix marks the item approved; it summarizes the edit as removing the outdated reference manuals, pointing 4.507.2 to the Energy Code, and striking the exception that referenced alternate design temperatures.

The supplement takes effect July 1, 2027 — but the design conditions it points to are enforceable today, because 150.0(h) already governs.

The multifamily footnote

One thing to confirm with your jurisdiction: the new pointers name only 150.0(h), which is the single-family mandatory-features section. The multifamily counterpart is Section 160.3(b) — "Dwelling unit space-conditioning and air distribution systems" — and it carries the same 68°F/75°F indoor design temperatures. The express terms don't spell out a multifamily pointer here, so treat 160.3(b) as the governing sizing rule for multifamily dwelling units and verify with your plan checker.

What to do now

You don't have to wait for 2027:

• Set design temperatures to the Energy Code's values — 68°F heating, 75°F cooling indoors; outdoor conditions within the 99%/1% bounds. Stop padding them under the CALGreen exception.
• Update load-calc report headers to cite Manual S-2023 (by way of 150.0(h)(5)) for equipment selection, not Manual S-2014.
• Expect one set of design conditions. For plan checkers, that's the payoff: Part 6 and Part 11 will finally ask for the same numbers.

And while you're re-checking equipment selection, remember most new heat pumps now ship with A2L refrigerant, which changed the machinery-room and charge math too. See the A2L Table 1102.3 breakdown for heat-pump plan check.

Confirm the governing requirements with your local authority having jurisdiction; this is a plan-check pointer, not legal advice.

What CrossBeam does with it

CrossBeam checks residential HVAC sizing against the design conditions that actually govern — the Energy Code's fixed 68°F/75°F indoor temperatures, the 99%/1% outdoor bounds, and ACCA Manual S-2023 equipment selection. So a load calc that leans on CALGreen's old "alternate design temperatures" exception gets flagged against 150.0(h) today, not only after the 2027 supplement lands.