Leisure Home HVACLeisure Home HVACAn Irvine HVAC contractor handles the furnace and its vent connector, while the masonry flue is checked separately. ClearView Air & Heat covers furnace work across Irvine; the orphaned-chimney issue below is common in older Woodbridge and Northwood homes with 1970s gravity furnaces.
| Task | Who does it / cost range |
|---|---|
| Furnace diagnostic visit | HVAC contractor, $90 to $180 |
| 80% AFUE furnace replacement (vents up chimney) | HVAC contractor, $2,500 to $5,000 |
| 90%+ AFUE condensing furnace (PVC sidewall vent) | HVAC contractor, $4,500 to $7,500 |
| Metal vent connector / B-vent replacement | HVAC contractor, $200 to $600 |
| Level 2 masonry chimney inspection | Chimney sweep, $150 to $400 |
| Clay-tile or stainless flue reline | Chimney sweep, $2,000 to $5,000 |
| Water-heater reline after furnace goes condensing | Chimney sweep, $1,500 to $3,500 |
Furnace-and-flue tasks: which trade, what it costs in Irvine
An Irvine HVAC contractor installs, repairs, and vents the gas furnace, including the draft hood, the metal vent connector, and the B-vent or PVC flue that carries combustion gas out of the house. A diagnostic visit runs $90 to $180 and covers the heat exchanger, gas valve, igniter, and flue draft. The contractor confirms the furnace vents safely but stops at the chimney wall, the brick chase, clay tile liner, and crown belong to a chimney sweep. The U.S. Consumer Product Safety Commission flags cracked heat exchangers and blocked flues as a leading source of furnace carbon-monoxide incidents, which is why draft testing is part of every furnace replacement.
A 90%+ AFUE condensing furnace vents through 2-inch to 3-inch PVC pipe out a sidewall, not up the chimney, costing $4,500 to $7,500 installed in Irvine. When that furnace comes out of a shared masonry flue, the chimney is left venting only the gas water heater, an undersized, oversized flue that now carries too little gas to stay warm. ANSI Z223.1 / NFPA 54, the National Fuel Gas Code, calls this an orphaned water heater and requires the flue to be resized or relined so the water heater drafts. The HVAC contractor identifies the problem; the reline itself is chimney-sweep scope.
Before a new furnace is tied into an existing brick chimney, a Level 2 inspection checks the clay-tile liner, the smoke chamber, and the flue sizing with a camera scan, costing $150 to $400. A flue that serves both a furnace and a fireplace must be lined and sized correctly or combustion gas can spill back into the living space. A chimney technician photographs the interior of the flue, measures clearances to combustibles, and confirms the crown and cap are intact before approving the connection, as Fluepro Chimney Sweep explains to customers. The Chimney Safety Institute of America sets the Level 1, 2, and 3 inspection standard that defines this scan.
A cracked heat exchanger or a blocked flue can push carbon monoxide into an Irvine home, which is why California requires a working CO alarm outside every sleeping area in homes with gas appliances. The U.S. Environmental Protection Agency notes that furnaces, water heaters, and fireplaces sharing a chimney are a common backdrafting path when one appliance is removed. The HVAC contractor tests furnace draft with a manometer and combustion analyzer; the chimney sweep clears creosote, nests, and spalled tile that the furnace tech cannot reach. Separating the trades keeps both the appliance and the flue certified against their own code sections.
A combined furnace-and-flue project follows a plain sequence. First, the HVAC contractor diagnoses the furnace and measures existing flue draft, $90 to $180. Second, if a condensing furnace is chosen, the contractor flags the orphaned water heater for a flue review. Third, a chimney sweep runs a Level 2 camera inspection, $150 to $400, and scopes any reline. Fourth, the furnace is installed and the PVC or B-vent is terminated per code. Fifth, final CO and draft testing confirms both the new furnace and the water heater vent safely. A straightforward 80% AFUE swap skips steps two and three because it keeps venting up the existing chimney.
Irvine's 1970s neighborhoods, Woodbridge, Northwood, University Park, still hold gravity and 80% AFUE furnaces vented up masonry chimneys that also serve a fireplace. Swapping to a condensing furnace in those homes almost always orphans the gas water heater and triggers a flue reline, adding $1,500 to $3,500 to the job. The City of Irvine requires a mechanical permit for furnace replacement, and California Title 24 energy rules push most new installs toward 90%+ AFUE units. South Coast Air Quality Management District rules also govern gas-appliance emissions across Orange County. Homes near the San Joaquin marsh and the coastal fog line see faster flue-cap corrosion, so cap and crown condition matters at inspection time.
An 80% AFUE furnace runs $2,500 to $5,000 installed; a 90%+ AFUE condensing unit runs $4,500 to $7,500. A required chimney reline can add $1,500 to $3,500.
When a condensing furnace stops venting up the shared chimney, the gas water heater is left alone in an oversized flue that no longer drafts, requiring a resize or stainless reline under NFPA 54.
Yes. The City of Irvine requires a mechanical permit for furnace replacement, and California Title 24 governs the efficiency rating of the new unit.
A gas-appliance flue should be inspected annually and before any furnace change-out; a Level 2 camera inspection runs about $150 to $400 in Irvine.