What this code requires
CALGreen 4.507.2 is the California Green Building Standards Code section that requires HVAC systems in new residential buildings to be sized using ACCA Manual J load calculations and Manual S equipment selection procedures. This means your heating and cooling equipment can’t be sized by rule-of-thumb or square footage alone — you need a load calc that accounts for insulation, window area, orientation, infiltration, and local climate data. The requirement applies to all new low-rise residential construction and additions that include a new or replaced HVAC system.
How to fix it
Hire an ACCA-certified Manual J load calc provider
The load calc must follow ANSI/ACCA 2 Manual J-2016 or an equivalent method, as CALGreen 4.507.2 states. Some mechanical engineers include this service; others don’t — ask upfront. Several software tools (Wrightsoft, Elite RHVAC, CoolCalc) output code-compliant Manual J reports. If you’re using a licensed HVAC contractor to prepare the calc, confirm they’re working from the permitted plans, not from a field measure of the existing system. The calc inputs — insulation R-values, window U-factors, infiltration rate, orientation — must match your permitted construction documents.
Run Manual J with the correct design conditions for your climate zone
California uses ACCA Manual J design conditions tied to each climate zone. The outdoor design temperatures and humidity levels for a project in San Diego differ significantly from those in Fresno or Sacramento. Using national default values instead of California-specific climate data is a common mistake that reviewers catch. Your software should pull from the ACCA Manual J Appendix tables for California, or from the Title 24 Part 6 Reference Appendices. Confirm the climate zone on your energy compliance documentation matches what’s entered in the load calc software.
Complete Manual S equipment selection using the Manual J outputs
Manual S is the step that matches actual equipment performance to your Manual J design loads. Pull the manufacturer’s published extended performance data (ARI/AHRI certified ratings at your actual design conditions, not just nominal tonnage). The selected equipment’s sensible and total capacity at design conditions must fall within the Manual S allowable range — generally 100% to 115% of the Manual J cooling load, and 100% to 140% for heating. Going oversized beyond these limits means the equipment short-cycles, fails to dehumidify, and doesn’t pass. Document the equipment model number, AHRI match, and the performance data table you used.
Assemble the documentation package for resubmittal
Your resubmittal needs at least three documents: (1) the full Manual J room-by-room load calc report — not just a summary page, but the complete output with all input assumptions shown; (2) the Manual S equipment selection worksheet or report showing the model selected, the AHRI-certified performance data at design conditions, and how the capacity lands relative to Manual J design loads; (3) an updated mechanical equipment schedule on the plans that matches the selected equipment model and tonnage exactly. Mismatches between the schedule and the Manual S model number are a separate correction trigger, so verify them before you submit.
Confirm duct system sizing does not conflict with the Manual D requirement
CALGreen 4.507.2 lists three methods: heat loss and gain per ANSI/ACCA 2 Manual J-2016, duct sizing per ANSI/ACCA 1 Manual D-2016, and equipment selection per ANSI/ACCA 3 Manual S-2014, or equivalents. Check whether your correction letter mentions duct sizing separately. Either way, Manual D sizing must be documented, as a separate report or as part of the mechanical plan set. Duct sizing done wrong will come back as a separate correction, so it’s worth addressing in the same round if it’s in scope.
Mark the revision on the title sheet and resubmit
Add a revision cloud and delta tag on the mechanical plans wherever the equipment schedule or notes changed. The title sheet should list the revision date and a brief description: “Added Manual J load calculation and Manual S equipment selection per CALGreen 4.507.2.” Attach the Manual J and Manual S reports as supplemental documentation — most jurisdictions accept them as separate PDF attachments rather than requiring them to be printed on the plan sheets. Confirm with your plan check portal whether they need to be uploaded separately or bundled into the plan set.
Take the CALGreen 4.507.2 fix steps with you
All 6 steps in one email, so you have them on site instead of on this page.
Why you got flagged
Plan-checkers flag 4.507.2 most often when the mechanical plans show equipment specs but nothing to justify the tonnage. If your sheet lists a 4-ton split system with no load calc attached, the reviewer can’t verify the sizing is correct — so it comes back as a correction. This is the most common version of this flag: the equipment is probably fine, but the supporting calculations are simply missing from the submittal.
A second pattern shows up on additions and remodels. The contractor replaces an old furnace or AC with a new unit, matches the existing tonnage, and submits without any load calc because the equipment footprint didn’t change. That’s not enough under CALGreen 4.507.2. If the scope of work triggers a full mechanical permit, the sizing documentation has to come along with it. Even if the existing unit was the right size, you still need the calc to prove it.
A third scenario involves design-build submittals where the equipment schedule shows high-efficiency variable-speed units. The plan-checker may accept that the equipment is good hardware, but Manual S requires you to match the selected equipment’s published performance data against the Manual J design conditions. Submitting a Manual J without a corresponding Manual S selection report — or using a Manual S from a different model year than what’s being installed — triggers the correction.
The official code
CALGreen 4.507.2 — Heating and Air-Conditioning System Design (California Building Standards Commission)
Read the source →