# §150.0(h): HVAC equipment sizing
What it requires
Heating and cooling equipment must be sized to the building's actual load using an ACCA Manual J calculation, with equipment selection per Manual S. The code limits how much the installer can oversize equipment, typically heating ≤ 140% of design heating load, cooling ≤ 115% of design cooling load.
The intent is to stop the historical practice of slapping a 5-ton AC on every house regardless of envelope, which leaves the equipment short-cycling and the homeowner uncomfortable.
When it applies
- Newly constructed dwellings.
- HVAC replacements in alteration scope (§150.2(b)), the new equipment has to be load-calc'd, not just "matched" to the old equipment.
- Additions where new HVAC capacity is being added.
How we use it
The CF1R lists the design heating and cooling loads in the equipment-sizing table. We compute them from the model's envelope + scope + climate-zone inputs; the responsible designer signs that the actual specified equipment falls within the §150.0(h) bounds. Our designer-CF1R checklist surfaces this as one of the eight inputs to confirm before the report goes out.
Common gotchas
- "Replacement-in-kind" HVAC swaps in alteration scope still trigger §150.0(h), the AHJ wants a load-calc, not a model-number match.
- Oversized heat pumps in mild climate zones (CZ3, CZ4, CZ6), the 140% heating limit caps capacity below what installers default to, which forces a conversation about staging or two-stage equipment.
- Manual D duct sizing isn't called out in §150.0(h) but is required by §150.0(m) for duct losses; the two travel together.