Furnace installation in our part of the North Bay - Novato, San Rafael, San Anselmo, Larkspur and Sausalito - usually starts with an old furnace that has reached the end - a cracked heat exchanger, a failed major part, or a unit that runs constantly and still leaves rooms cold. Replacing it well means more than swapping boxes. The new furnace has to be sized for the house as it is today, vented correctly for its type, and matched to ductwork that can carry its air.
When a new furnace makes sense
- The old furnace needs replacement. The heat exchanger is cracked, or an older furnace needs an expensive part.
- The heating is inefficient. Bills keep rising and the furnace runs long cycles to keep up.
- Capacity problems. Some rooms never warm up, or the furnace is so oversized it short-cycles.
- New construction or an addition needs heat where none existed.
- You want a different fuel or higher efficiency - from an old standard unit to a condensing furnace, or from gas to a heat pump.
If one part failed on a furnace that is otherwise sound, furnace repair is usually the better answer, and we will tell you so.
Sizing for the house you have now
Many furnaces in older homes were oversized when they went in, and the houses have changed since: new windows, added insulation, a remodeled attic. We run a load calculation room by room rather than copying the old furnace’s rating. A correctly sized furnace runs longer, steadier cycles, which is quieter, kinder to its parts and more even from room to room.
Efficiency and venting
The choice between a standard and a high-efficiency furnace is mostly a venting question:
- Standard (non-condensing) furnaces send hot exhaust up a metal flue or chimney. They suit homes where the existing vent is sound and there is no good drain route.
- High-efficiency (condensing) furnaces cool the exhaust enough to condense water out of it. They vent through plastic pipe, usually out a side wall or the roof, and need a condensate drain - which can be a puzzle in a crawlspace or attic.
One detail people miss: if a gas water heater shares the chimney with the old furnace, switching to a condensing furnace leaves the water heater alone in a flue sized for two appliances. That vent then has to be checked and often resized or relined. We look at this during the assessment, not on installation day.
Fuel and system choices
- Gas furnace: the usual like-for-like replacement where gas is already in place.
- Electric furnace: simple, for homes without gas, though heating costs depend heavily on electricity rates.
- Heat pump: heats and cools with one outdoor unit and suits Marin’s mild winters; see heat pump services.
- Dual fuel: a heat pump paired with a gas furnace that takes over on the coldest mornings.
Where the furnace goes
Furnaces here sit in hall closets, garages, attics and tight crawlspaces. Each location takes a different configuration - upflow, downflow or horizontal - and some access hatches are small enough to limit which models fit at all. Replacing an old gravity furnace is a bigger project, because it has no blower and its wide ducts rarely suit a modern furnace, so new ductwork is part of the plan. If existing ducts are leaking or crushed, we fix them with duct repair rather than connecting a new furnace to old losses.
Installation day
- In-home heating assessment and load calculation, done before the quote.
- Equipment recommendations with more than one option and an itemized price.
- Removal of the old furnace and installation of the new one, with new venting and a drain where needed.
- Gas pressure, temperature rise across the heat exchanger, combustion and every safety control are tested and set.
- The thermostat is set up for the new furnace.
- A final safety inspection, paperwork and warranty registration, and a walk-through of filter changes.
The furnace carries the manufacturer’s warranty and our installation carries a labor warranty. We install all major brands, including Carrier, Lennox, Trane and Goodman. Local pages: furnace installation in Novato and in San Rafael.