How to pass a HERS test on an alteration

By Roman Leonelli, CEO & Certified HERS / ECC Rater — CHEERS Rater #RCN13486. Published June 11, 2026.

This guide is about alterations — HVAC change-outs, additions, and remodels on an existing home, which is where the vast majority of HERS tests happen. New-construction whole-house verification follows a broader path; everything below is the change-out and remodel case.

Why “pass the first time” is the whole game

A HERS / ECC rater is an independent third party by regulation — the company that installs or corrects the work cannot also verify it. That single rule is why preparation matters so much: the rater can show your contractor exactly what failed and retest, but cannot pick up a roll of mastic and pass you. So a measure that isn't ready when the rater arrives becomes either a same-visit fix (if your installer is on site) or a return trip (if they're not).

The return trip is the expensive part — not so much the retest fee as the schedule. A duct test that doesn't pass can hold up drywall, a final inspection, or an escrow date. Get the measures right before the visit and the test is a 30-to-60-minute formality with a same-day passing CF3R at the end of it. For what a first visit runs across the market, see our HERS test cost guide; for what happens when something doesn't pass, see what happens if you fail a HERS test.

What triggers a HERS test on an alteration

Two common scopes pull a HERS test onto an existing home:

• Replacing space-conditioning equipment. Swapping the outdoor condenser, cooling or heating coil, air handler, or furnace heat exchanger is an “altered space-conditioning system” under Title 24 section 150.2(b)1E — the classic HVAC change-out.
• Installing more than 25 feet of new or replacement ducts. Section 150.2(b)1D sets the trigger at 25 feet under the 2022 code — tighter than the 40-foot rule many contractors still quote.

Which specific measures apply depends on what you touched and on your climate zone. The authoritative list for your job is printed on the registered CF1R (Certificate of Compliance) prepared for the permit — read it before you order equipment, because it tells you which tests are coming.

The alteration HERS measures — and how to pass each

1. Duct leakage (the one that fails most)

The rater seals the registers, pressurizes the duct system to 25 Pascals with a calibrated fan, and reads leakage as a percentage of system air-handler airflow. The target is about 10% on an altered system and 5% on an entirely new or complete-replacement one (sections 150.0(m)11 and 150.2(b); your CF1R has the exact number). On a typical 3-ton system that moves 1,200 CFM, a 5% target is only 60 CFM of allowable leakage — there isn't much room.

How to pass:

• Seal with mastic, not cloth duct tape — tape fails within a season and the rater can see it.
• Hit the usual suspects: register boots, the supply plenum, and every takeoff connection.
• Walk the attic for a run that was knocked loose or never reconnected — one open run sinks the whole test.
• Have the installing contractor on site so a borderline result gets sealed and retested in the same visit. More detail on our duct leakage testing page.

2. Refrigerant charge verification

For an air-conditioner alteration, prescriptive refrigerant charge verification applies in the hotter inland zones — Climate Zones 2 and 8 through 15 — so a coastal Climate Zone 6 change-out usually doesn't require it under the 2022 code. Under the 2025 Energy Code (permits on or after January 1, 2026), heat-pump change-outs require it in all 16 climate zones. One catch worth building your schedule around: charge can't be verified until airflow passes, because the readings depend on airflow across the coil.

How to pass:

• Weigh in the charge to the manufacturer's spec for the actual line-set length and metering device — don't leave it at the factory pre-charge on a long line set.
• Verify subcooling or superheat per the equipment's installation instructions, not by feel.
• Make sure the coil and filter are clean and airflow is already passing before the charge is checked.

3. System airflow

A ducted cooling system has to deliver at least 350 CFM of airflow per ton of cooling capacity. Airflow failures are almost never the equipment — they're undersized or restrictive return ducts, crushed or kinked flex, a dirty filter, or a high-resistance filter grille.

How to pass: size the returns for the equipment, put in a fresh filter, open every register and damper, and clear any crushed flex before the visit. These are the cheapest points on the whole test.

4. Fan efficacy (watt draw)

The blower has to move that air without exceeding the fan-watt-draw limit on your CF1R — a measure of how efficiently the air handler pushes air. Restrictive ductwork makes the blower work harder and pushes watt draw up, so the fix is usually the same as the airflow fix: lower the static pressure the system is fighting.

How to pass: a properly sized return and a low-static filter do most of the work; an ECM/variable-speed blower has more margin than a fixed-speed PSC motor.

5. Ventilation: whole-house IAQ and the kitchen hood

Larger remodels and added conditioned space can pull in mechanical ventilation under ASHRAE 62.2 — a whole-dwelling ventilation fan sized to the house, with the measured airflow verified in the field — and a kitchen remodel can trigger range-hood airflow verification. These surface less often than the HVAC measures, but when they're on the CF1R they're verified the same way: measured against a target, pass or fail.

How to pass: install the fan the CF1R calls for (not a smaller one), duct the range hood to the outside rather than recirculating, and confirm the rated airflow is actually achievable through the installed ducting.

The pre-test checklist that gets you a first-try pass

• Have the installing contractor on site for the test. The single highest-leverage move — it turns most failures into same-visit fixes.
• Mastic-seal accessible duct connections before the rater arrives. Boots, plenum, takeoffs — never cloth tape.
• Fresh filter in, every register and damper open, power on. Three free points of airflow.
• Weigh in refrigerant to the line-set spec. And make sure airflow passes first, or the charge can't be verified.
• Confirm the installed equipment matches the CF1R and the CF2R is registered. A paperwork mismatch stalls verification as surely as a failed measure — see what HERS / ECC testing covers.

A quick note on the name: HERS is now ECC

As of January 1, 2026 the California Energy Commission renamed the code-compliance side of the HERS program ECC (Energy Code Compliance), so you'll see “HERS rater” and “ECC rater” used interchangeably — same field tests, same forms, same registries, per the CEC's Energy Code Compliance Program. ERE registers every passing CF3R with CHEERS, an approved ECC data registry. If you want the full permit-to-sign-off sequence, our Title 24 compliance checklist lays it out.

Frequently asked

How do I pass a duct leakage test on a change-out?

Seal the duct system with mastic — not cloth tape — before the rater arrives, paying special attention to register boots, the plenum, and takeoff connections, and make sure no runs are disconnected in the attic. The rater pressurizes the system to 25 Pascals and measures leakage as a percentage of system airflow: about 5% for an entirely new or replacement duct system and 10% for an altered existing system. Having the installing contractor on site means a borderline result can be sealed and retested the same visit.

What is the passing score for a HERS duct leakage test?

On an alteration, the common target is 10% of system air-handler airflow; an entirely new or complete-replacement duct system has to hit 5%. The exact target for your project is printed on your registered CF1R, because it depends on the scope of work and the duct location. Those thresholds come from Title 24 sections 150.0(m)11 and 150.2(b).

Does my air-conditioner change-out need refrigerant charge verification?

For an air-conditioner alteration, prescriptive refrigerant charge verification is required only in the hotter inland climate zones — California Climate Zones 2 and 8 through 15 — so a coastal Climate Zone 6 change-out usually does not require it under the 2022 code. Under the 2025 Energy Code (permit applications on or after January 1, 2026), heat-pump change-outs require refrigerant charge verification in all 16 climate zones. Your CF1R lists the measures that actually apply to your address and scope.

Can the HERS rater fix the problem and pass me?

No. HERS / ECC raters are required to be independent third parties, so the same company cannot install or correct the work and then verify it. What the rater can do is show your contractor exactly what failed, where, and by how much, then stay and retest once it is corrected.

Can I pass a HERS test the same day?

Yes. If the installing contractor is on site, most borderline measures — duct leakage, refrigerant charge, airflow — can be corrected and retested in the same visit, and ERE registers the passing CF3R with CHEERS the same day. The single biggest cause of delay is a return trip for a fix that could have been made on the spot.