HVAC in Marin County

Reading the symptom before spending money

A diagnosis worth paying for identifies the failed component and explains why it failed, because the second half predicts whether the repair holds.

• Blower runs, air is not warm. On gas equipment, usually ignition or flame sensing. On a heat pump it can mean the system dropped to auxiliary electric heat because the outdoor unit is not producing.
• Short cycling. Bursts of on and off point to an oversized unit, a restricted return, a clogged filter or a failing safety switch. Oversizing is common here because the old unit's rating gets copied instead of the house being measured.
• Outdoor unit hums, fan does not spin. Typically a capacitor or a fan motor. Worth fixing immediately, because running a condenser with a dead fan cooks the compressor.
• Cooling capacity fading across a season. That is a leak, and topping off refrigerant without locating it is a repeating charge.
• Rooms that never match the thermostat. Usually distribution: crushed flex duct, leaking plenums, undersized returns, or one zone trying to serve a two-level hillside house.

We find rodent damage in Marin crawl spaces and attics often enough to check by default, and chewed flex duct produces symptoms that read like an equipment fault until someone goes under the house.

The Ross Valley and the San Geronimo Valley. Larkspur, Kentfield, Greenbrae, Ross, San Anselmo and Fairfax hold older cores where wall and floor furnaces are still in service, and the redwood canyons behind them stay cool and damp long after the rest of the county warms up. Out toward Woodacre, San Geronimo, Forest Knolls and Lagunitas, access rather than equipment often shapes the job.

San Rafael and Novato. Here Marin gets real summer heat and central systems make the most sense. Postwar and later subdivisions generally have duct runs already in place, garages with room to work, and setback for an outdoor unit.

The Eichlers. Marin's Eichler tracts are Terra Linda and Lucas Valley / Marinwood in San Rafael, a small cluster in Strawberry in Mill Valley, and a handful in Sleepy Hollow in San Anselmo. They were built with radiant tubing cast into the slab, flat roofs, no attic, and glass walls where a conventional system wants a wall cavity. When the slab loop stops performing, a bigger boiler is not the automatic answer, and we treat that as its own discipline on our Eichler home services page.

One thing does not vary anywhere in the county: all of Marin sits inside the Bay Area Air Quality Management District. In Sonoma County the district changes from town to town, which changes which appliance rules apply. In Marin it does not, so every jurisdiction here works from the same district rules.

Distribution first, then capacity, then envelope

Most homeowners open with the brand question. We start three steps earlier, and every Marin replacement runs through the same test in the same order.

First, distribution. Where can conditioned air actually travel in this house? Serviceable existing ductwork keeps a central system on the table and is usually the least disruptive path. Undersized, leaking or crushed ducts will disappoint you no matter what is on the label. No duct system at all, which describes a great many Marin cottages and hillside houses, narrows the real options to ductless mini-splits, small-duct high-velocity, or a hydronic approach. That answer eliminates more choices than anything else on the list.

Second, capacity. A heat pump replacing a gas furnace adds electrical load, which makes the panel part of the mechanical project. The deciding document is a load calculation, not a glance at the breaker panel. Where a panel or service upgrade is needed we handle it under our own C-10 license instead of handing you a second contractor, as described on our electrical page for Marin County.

Third, envelope. Leaking ducts in a vented crawl space, an uninsulated attic, or a wall of west-facing single-pane glass will defeat correctly chosen equipment. Sizing to a poor envelope produces an oversized unit that short cycles and wears out early, and sometimes the highest-return item in a proposal is duct sealing and return air correction rather than the machine.

With those three answers the equipment choice nearly makes itself. A gas furnace paired with an air conditioner remains sound in a ducted inland house. A heat pump moves heat rather than generating it and covers both seasons from one outdoor unit, which suits Marin well because winters here rarely reach the temperatures where capacity falls off and the auxiliary electric heat strip has to carry the load. Inverter-driven equipment modulates instead of slamming between full output and off, which matters more in a mild shoulder-season climate than anywhere with a brutal winter. Dual fuel keeps a gas furnace behind a heat pump, and ductless multi-zone systems solve the no-duct house.

Permits, code and inspection across Marin's jurisdictions

Marin permits mechanical work through a lot of separate counters, and knowing which one applies is half the scheduling problem.

• A permit is required, including for a like-for-like changeout. Furnace, air conditioner, heat pump and ductless installations are permitted mechanical work in every Marin jurisdiction. We pull it; the homeowner should not be asked to.
• Each incorporated city and town runs its own building department: Belvedere, Corte Madera, Fairfax, Larkspur, Mill Valley, Novato, Ross, San Anselmo, San Rafael, Sausalito and Tiburon. Forms, requirements and turnaround are not uniform across them.
• Everything outside those boundaries is unincorporated Marin, including West Marin and the San Geronimo Valley, and it permits through the Marin County Community Development Agency.
• Title 24 applies to replacements, not only new construction. California's 2025 Building Energy Efficiency Standards took effect January 1, 2026, per the California Energy Commission. Which compliance path and verifications a changeout triggers depends on scope, so we confirm that with the jurisdiction first. Where third-party verification of duct leakage or refrigerant charge is required, we schedule it rather than leaving it as a homeowner errand.
• CALGreen is a new-construction code. CALGreen, Title 24 Part 11, is described by the state as "the first-in-the-nation mandatory green building standards code," and its provisions apply to new construction. Replacing equipment in an existing Marin house triggers no CALGreen retrofit obligation.
• Air district appliance rules are live and changing. Zero-NOx requirements for residential water heaters under Regulation 9, Rule 6 begin in 2027 with compliance dates that vary by unit size, and fan-type central furnaces come on a later phase. Nobody's existing gas appliance is banned, and we verify what applies when your project is scheduled.
• Inspection focuses on what is easy to skip: condensate routing and termination, combustion air and venting on gas equipment, working clearances, the disconnect at the outdoor unit, and secure duct connections.
• On tight southern Marin lots, outdoor unit placement is its own constraint. We settle where the condenser can physically and legally sit before equipment is ordered.

What the price is made of

No two Marin quotes are comparable until you know what each one includes, so here is what moves the number.

Distribution dominates. Sound existing ductwork is the least expensive path to a new system, and a house with no ducts is a larger project regardless of brand, because the cost lives in line sets, indoor heads, chases and drywall repair rather than in the box outside. Access is next, and it is unusually significant here: a Sausalito or Tiburon house reached by three flights of exterior stairs with no driveway consumes labor the same equipment would not consume in a Novato garage, and West Marin adds distance to every trip.

Electrical scope is third. If the panel carries the new load, that line item disappears. If it does not, a subpanel or service upgrade enters the project, and some proposals quietly omit it so the bid looks lower. Equipment tier matters less than people expect: modulating systems earn their premium through comfort and long low-output run times rather than raw output. Zoning is its own multiplier, since every added ductless head or damper zone brings labor, controls and refrigerant line with it.

Then the site conditions particular to this county. Near the water, corrosion-resistant coil coatings and hardware belong on the specification, and skipping them is a way to buy the same condenser twice. On canyon lots, placement may force a longer line set. Envelope repair and return air correction appear when the equipment cannot perform without them, and permit and verification scope rounds out the list.

Incentives, and what is open right now

Incentive pages age badly, so treat anything you read elsewhere as a starting point and confirm it at project time.

MCE is Marin's community choice electricity provider. Rather than publishing one flat residential HVAC rebate, MCE routes homeowners through a rebate finder, and its own page notes that "if you're part of an income-qualifying household, you might be eligible for extra savings." Start at MCE's heat pump rebates page and check what applies to your address and household.

Sonoma Clean Power programs are not available in Marin. SCP serves Sonoma County only, so a Marin homeowner who finds an SCP heat pump offer while searching is looking at a program they cannot enroll in. That trips people up constantly on this side of the county line.

The conditions matter more than the amount. MCE's heat pump rebates turn on three conditions rather than on an amount: twelve months of ownership and residency in a single-family detached home inside MCE territory, a participating contractor who processes the application on your behalf, and an application filed before the equipment goes in, since MCE will not apply a rebate retroactively.

Power outages, and what keeps the heat on

PG&E may turn off power during severe weather to help prevent wildfire, through the program it calls a Public Safety Power Shutoff. Hillside and rural circuits in Marin carry more of that exposure than dense flatland neighborhoods.

The mechanical consequence is often overlooked: a gas furnace still needs electricity for its blower, controls and ignition, so gas heat is not outage-proof heat. If keeping conditioned air moving through an outage matters to your household, the answer is a backup power plan rather than a different furnace. We are a Certified Generac Generator installer, and battery storage paired with solar in Marin County is the other route. Either way, the load calculation that decides what backup can carry is the same document the heat pump conversation needs.

Maintenance that is worth the visit

What a service visit does concretely: keeps the filter and blower wheel clean so airflow stays where the equipment was designed to operate, clears the condensate drain before it backs up into a pan or a ceiling, verifies refrigerant charge against measured conditions instead of a gauge glance, tightens electrical connections that vibrate loose, checks combustion and venting on gas equipment, and washes the outdoor coil.

Marin adds three reasons to keep the interval short. Salt air near the bay and the coast attacks outdoor coils and fasteners, and regular rinsing is the cheapest life extension available. Canyon and wooded lots pack coils with redwood needles, oak leaves and cobwebs, which quietly steals capacity. Rodent pressure damages duct and control wiring, and finding it during a scheduled visit beats finding it on the first cold night. Our maintenance plans exist to make that timing automatic.

Choosing a contractor for this work

Ask these things and the field narrows quickly.

Confirm the license class fits the work: C-20 for HVAC, and C-10 if the job touches the panel. We hold C-20, C-10 and C-36, so a project that crosses trades does not cross companies. Ask for a load calculation rather than a size copied off the old data plate. Ask directly who pulls the permit, because a contractor suggesting you pull it is moving liability onto you. Ask what the proposal covers on distribution, since two quotes listing identical equipment can differ entirely in ductwork scope. Ask how manufacturer standing affects your warranty: Mitsubishi Diamond Contractor Elite and Trane Comfort Specialist are tiers the manufacturers award, and they influence registration, parts access and extended terms.

We are also Diamond Certified and hold a BBB A+ Rating. We handle commercial HVAC across Marin as well, a different discipline worth confirming when the building is not a house.

What North Bay homeowners say

Two reviews from customers, in their own words.