August 13, 2026
A routine HVAC replacement can trigger California Title 24 compliance requirements most homeowners never saw coming. Here's what you need to know before the work begins.
You called for a replacement. Maybe your AC finally gave out during one of those late-summer heat waves that roll through the inland parts of San Mateo County, or your furnace has been limping along for years. Either way, you expected a straightforward job. Then your contractor started talking about Title 24, HERS raters, duct pressure tests, and compliance forms — and suddenly a replacement turned into something that feels a lot more complicated.
You’re not alone. This catches a lot of homeowners off guard. Here’s a plain-language breakdown of what California’s Title 24 energy code actually requires for HVAC work, what triggers it, and what it means for your project.
California’s Title 24 Building Energy Efficiency Standards are the state’s rules for how buildings use energy. They cover everything from insulation and lighting to the HVAC systems that heat and cool your home. The California Energy Commission updates these standards on a three-year cycle — the current version took effect January 1, 2026, applying to any project that pulled a permit on or after that date.
The core purpose is to reduce energy waste. But for homeowners, what matters most is this: Title 24 is not just a new-construction rule. It applies to alterations, replacements, and additions on existing homes too. That means if you’re pulling a permit for HVAC work — which you’re legally required to do for most jobs — your project has to meet current energy code requirements, regardless of how old your home is.
This is the question most homeowners are actually asking when they land on a page like this. Not the theory — the practical answer. Does my specific project require all of this?
The short version: if your project requires a mechanical permit, it almost certainly triggers Title 24 compliance. That covers replacing an AC condenser, swapping out a furnace, installing a new evaporator coil, adding or replacing more than 40 feet of ductwork, or relocating any HVAC equipment. Even a like-for-like swap of the same system type requires a permit in California — and once a permit is pulled, the energy code follows.
There’s a common misconception worth addressing directly. A lot of homeowners assume that replacing an old unit with a newer version of the same thing is exempt from compliance because nothing is technically “changing.” That’s not how California reads it. The permit is the trigger, and the permit is required. Any contractor telling you otherwise is either misinformed or suggesting you skip the permit entirely — which creates a much bigger problem down the road.
What does compliance actually require once it’s triggered? At minimum, your new equipment must meet current efficiency thresholds. Under the 2026 code, that means central air conditioners need to hit at least 15.2 SEER2. Gas furnaces must reach at least 90% AFUE in most California climate zones. Your duct system must be tested for leakage — and if it fails, it needs to be sealed before the project can be finaled. Ducts in unconditioned spaces like attics or crawlspaces must be insulated to at least R-6. Your thermostat must be capable of setback scheduling and demand response — meaning it needs to be able to respond to grid signals, not just a basic programmable unit.
And then there’s the HERS rater. A certified Home Energy Rating System inspector — someone completely independent from your HVAC contractor — must physically verify that the work meets code before a Certificate of Occupancy is issued. This is not optional, and it’s not something your contractor can do themselves. The rater visits the job site, performs a duct pressure test, and signs off on a compliance form called the CF3R. Your contractor handles the CF1R before installation and the CF2R after, but the CF3R belongs to the rater alone.
Here’s something that surprises a lot of people. PG&E estimates that the average single-family home in California has duct leakage somewhere between 30% and 40%. Title 24 requires altered duct systems to stay below 15% leakage — and new construction must come in under 6%. That gap is significant.
What it means in practice is this: the moment you replace your HVAC system in a home with aging ductwork, your ducts will almost certainly be tested. And there’s a real chance they’ll fail. When that happens, the contractor has to seal it and retest before the permit can close.
San Mateo County has a lot of homes built between the 1940s and 1980s. These are well-built houses in established neighborhoods, but their duct systems were never designed to meet today’s leakage standards. The coastal marine climate here — the fog, the humidity, the salt air that accelerates corrosion in outdoor HVAC components — doesn’t help. Ductwork in attics and crawlspaces in this region takes a beating over decades, and most of it has never been pressure-tested.
When a duct system fails the HERS leakage test, the contractor has to seal it and retest before the permit can be closed. That adds time and cost to the project. The way to avoid that outcome is to work with a contractor who treats duct sealing as part of the installation — not as a patch job after a failed inspection. Sealing ducts to Class A standards from the start, rather than waiting to see what the rater finds, is the difference between a project that closes cleanly and one that drags on.
The financial stakes are real in this market. With median home values in San Mateo County consistently above $1.5 million, an open permit or non-compliant HVAC installation isn’t just a code issue — it can surface during a home inspection and complicate or delay a sale. Buyers’ agents know what to look for, and unpermitted work is one of the first things that comes up.
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Title 24 doesn’t just govern the process — it shapes which systems you can actually install. Not every unit on the market qualifies. The equipment has to appear in the California Energy Commission’s Appliance Efficiency Database with ratings that meet or exceed the current minimums. Your contractor should be verifying this before recommending a system, not after.
The 2026 code raised the bar from previous cycles. The 15.2 SEER2 minimum for central air conditioners reflects a shift to a new testing methodology that more accurately measures real-world efficiency. If you’re comparing quotes and one contractor is recommending a system that doesn’t meet this threshold, that’s a problem — not just for compliance, but for long-term operating costs.
Efficiency ratings are only part of the picture. Title 24 also requires that HVAC systems be sized using ACCA Manual J load calculations. This is a formal method for determining exactly how much heating and cooling capacity a home actually needs, based on square footage, insulation levels, window orientation, local climate data, and other factors specific to the structure.
Oversized equipment is one of the most common problems in residential HVAC, and it’s not just a comfort issue. A system that’s too large for the space cycles on and off too frequently, never runs long enough to properly dehumidify the air, wears out faster, and wastes energy. Title 24’s sizing requirement exists precisely to prevent this — and a contractor who skips the Manual J calculation and just recommends “the same size as what you had” is not meeting code.
For San Mateo County homeowners, this matters more than it might seem. The county spans a range of microclimates — from the fog-cooled coastline near Daly City to the warmer inland neighborhoods of Redwood City and Woodside, where summer temperatures can climb significantly higher than the coastal average. A load calculation that accounts for your specific location within the county will produce a more accurate equipment recommendation than a one-size-fits-all approach.
Thermostat requirements are another piece that catches people off guard. The 2026 code requires new HVAC installations to include a thermostat that’s capable of demand response — meaning it can receive and respond to signals from the utility grid during peak demand periods. This doesn’t mean PG&E controls your thermostat. It means the device has to be capable of participating in demand response programs if you choose to enroll. Basic programmable thermostats don’t qualify. A smart thermostat that meets the Joint Appendix 5 (JA5) requirements does.
One of the things that makes Title 24 feel opaque is the paperwork. There are three compliance forms involved in every permitted HVAC project, and understanding what each one does makes the whole process feel a lot less mysterious.
The CF1R is the Certificate of Compliance. Your HVAC contractor prepares this before installation begins. It documents the planned scope of work — the equipment being installed, the efficiency ratings, the duct design, the sizing calculations — and confirms that the project as designed meets Title 24 requirements. Think of it as the plan on paper.
The CF2R is the Certificate of Installation. Your contractor completes this after the work is done. It confirms that what was actually installed matches what was documented in the CF1R. Equipment model numbers, duct sealing methods, thermostat type — all of it gets recorded here.
The CF3R is the Certificate of Verification. This one belongs to the HERS rater, not the contractor. After installation is complete, the rater visits the site, performs the duct leakage pressure test, verifies refrigerant charge, and confirms that the installed system matches the compliance documentation. Once the CF3R is signed and submitted, the permit can be finaled.
The reason this three-step process exists is consumer protection. The HERS rater is an independent check on the contractor’s work — someone with no financial stake in the outcome who verifies that what was promised was actually delivered. In a market where HVAC labor runs $150 to $200 per hour and a full system replacement is a significant investment, that independent verification matters. When a contractor coordinates this process smoothly — handling the CF1R and CF2R, scheduling the rater, and building duct sealing into the installation rather than treating it as an afterthought — the project closes faster and cleaner.
Title 24 compliance isn’t something that should fall on the homeowner to figure out. The right contractor handles it — pulls the permit, prepares the compliance forms, coordinates the HERS rater, seals the ducts properly the first time, and installs equipment that actually meets the current efficiency minimums. What you should walk away from a project with is a finaled permit and a system that was installed correctly, not a stack of open questions and a permit that never closed.
If you’re planning an AC replacement, a furnace swap, or any HVAC work that requires a permit in San Mateo County, we’re glad to walk you through what your specific project will involve before any work begins. No surprises, no pressure — just a clear picture of what compliance looks like for your home.
We’ve been doing this work in San Mateo County for four decades. Reach out by phone or text at 650-690-6175 to get a free quote and straight answers about what your project requires.
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