What this code requires
CALGreen 4.504.1 is the California Green Building Standards Code section that requires all duct openings and mechanical system openings to be covered during construction to prevent dust, debris, and construction particles from entering the HVAC system. The requirement applies to new residential construction and additions where ductwork is installed before occupancy. Any permit that includes new ductwork or air-handling equipment will hit this section if the plans do not include a note documenting how openings will be protected through the construction phase.
How to fix it
Add a duct protection note to the mechanical sheet
On your mechanical plan or the sheet containing the duct layout, add a note that reads: 'All duct openings and mechanical system openings shall be covered during construction to protect against contamination per CALGreen Section 4.504.1.' This note must appear on the set before the city will sign off. Keep it visible, not buried in small general notes at the edge of the page. If you use a standard notes block, add it as its own line item rather than folding it into a catch-all CALGreen compliance note.
Add the same note to the general construction notes
Reviewers check multiple sheets and not all of them pull the mechanical plan. Put the identical duct-protection note on your title sheet or general construction notes as well. When both sheets carry the note, there is no ambiguity about whether it was addressed. Duplicate notes are not a problem. A missing note is. If your office uses a standard CALGreen checklist sheet, confirm that 4.504.1 is explicitly checked off there too.
Specify the covering method if the jurisdiction requires it
Some cities want the specific method called out on the plans. The code accepts tape, plastic, sheet metal, or other methods acceptable to the enforcing agency, such as temporary caps or manufacturer-supplied plugs on boot openings. If your city's checklist asks for this level of detail, add a line to the note: 'Openings shall be covered with tape, plastic or sheet metal until final startup of the heating, cooling and ventilating equipment.' If the city's standard notes are silent on the method, the basic section citation is typically enough. Check the city's CALGreen residential checklist before your first submittal to confirm what level of detail they expect.
Call out new boot cuts on remodel projects specifically
On remodel permits, the flag often comes from new supply or return boot openings cut into existing ductwork. Your plan should label those new openings and include the protection note covering those specific locations. If you are adding three new boots to an existing system, the note should make clear that all three will be covered until the registers are installed and the system is ready to run. This is a common gap on partial HVAC remodel plans that otherwise handle existing equipment well.
Coordinate with your HVAC sub before rough-in starts
At inspection, a field inspector can write a correction if duct boots are open and dusty with no evidence they were protected. Talk to your HVAC sub before rough-in and confirm they know the requirement. Have them cap all boot openings as soon as they are cut. Inspectors are not looking for a specific brand of cap; they want to see openings not left exposed through drywall, texture, or other dusty trades. A quick walk-through before the inspector arrives takes five minutes and prevents a re-inspection fee.
Mark the added note with a revision cloud on resubmittal
When you resubmit after a duct-protection correction, mark the new note with a revision cloud and revision number. Some plan departments will bounce a resubmittal if the correction response is unclear about where the fix appears on the sheet. A revision cloud over the mechanical note, with a matching description in the response letter, closes the loop. Your response letter should say: 'CALGreen 4.504.1: duct protection note added to mechanical plan, Sheet M1, revision 2.' That is all it takes.
Take the CALGreen 4.504.1 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
Here's why plan-checkers flag this: the correction almost always comes down to one missing line on the mechanical or general notes sheet. The plan set shows the duct layout and equipment specs, but says nothing about protecting those openings while framing, drywall, and finish work happens around them. A reviewer reads through the mechanical schedule, sees no duct-protection note, and writes the correction.
The second scenario is a partial note that doesn't name a method. Something like 'contractor to protect ducts during construction' satisfies no one. The code wants confirmation that a specific action will happen: the openings will be covered. A note that passes says exactly that.
A third flag comes up on remodel permits where new supply or return boots are cut into existing ductwork. The plan shows the new boot locations but doesn't address what happens to those fresh openings before the registers go in. Drywall dust is a real problem here. Once it's in the duct system, you're cleaning filters or replacing equipment long after the job is done.
Finally, some contractors note the duct protection requirement on one sheet and not the other. If your mechanical plan shows it but the construction notes on the title sheet are silent, different reviewers check different sheets and one of them will flag it. The fix is the same note in both places.
The official code
CALGreen Part 11 Section 4.504.1 — Duct Opening Protection, California Building Standards Commission (DGS)
Read the source →