Who actually needs a furnace in Gainesville (fewer homes than you'd think)

Start with the year on the deed

Gainesville’s housing stock sorts into eras, and each era tells us roughly what is heating the house today.

The early-1900s wood-frame homes of Duckpond, Pleasant Street and the Southeast district were built with no ducts at all; whatever central system is there now was threaded into an attic decades later. About 42 percent of the city’s homes predate 1980, and the big 1970s cohort across Northwest Gainesville, from NW 8th Avenue up past NW 53rd, mostly got electric air handlers with strip heat, the cheapest thing a builder could install. Haile Plantation and the 1990s pool neighborhoods were built around heat pumps. Oakmont and the Town of Tioga are almost all heat pumps, some with gas as an upgrade.

The homes that genuinely benefit from a Lennox furnace are a slice of the first two groups: inside GRU’s natural gas territory, already piped for gas, and owned by someone who finds heat pump air on a freeze morning unsatisfying. That is a real group in this town. It is not most of it.

The problem a furnace solves here

A heat pump loses efficiency as the outdoor temperature falls. On the seventeen or so nights a year that Gainesville drops below freezing, and the few that reach 28, it leans on electric backup strips and the supply air feels merely warm. A gas furnace does not care what the thermometer says; it burns fuel and delivers hot air at the register. For a drafty 1920s house under the oaks, that difference is comfort. For a 2015 house in Oakmont with modern insulation, it is barely noticeable.

Dual-fuel is the middle path: a heat pump for mild winter days, a gas furnace that takes over below a set temperature. Where gas is already present, it is what we most often recommend.

Tiers, in plain terms

• Single-stage. Burner is on or off. Lowest cost, fine for a small, well-insulated house or a rental.
• Two-stage. A low setting for most of the winter and a high setting for the cold snaps. Steadier, quieter.
• Variable-capacity. The burner modulates in small steps and the blower matches it. Best summer humidity control, since the same blower runs the cooling coil.

Efficiency is stated as AFUE; higher is better, and the condensing models vent through plastic pipe.

Installing one in an older Gainesville house

Three things come up on nearly every furnace install here. Clearance: 1970s utility closets were sized for a skinny electric air handler, and a furnace with a coil on top may need the closet opened up. Venting and drainage: condensing furnaces produce acidic condensate that must drain, and on a slab that means a condensate pump, which the aquifer water, at roughly eight grains hard, will scale unless it is serviced. Gas supply: GRU has to have gas at the meter, and the interior line has to be sized for one more appliance. Addresses on Clay Electric or in Alachua and Newberry’s municipal electric areas without gas would need propane, a different conversation.

Keeping it running

A furnace here runs its burner perhaps 300 hours a year and its blower for 3,000. Care follows that ratio: a heating check before the freeze window opens in early December, with burner, igniter, flame sensor and flue inspected, and the same coil and filter attention any air conditioner needs. Oak pollen from late January coats a filter fast, and a plugged filter trips the high-limit switch and shuts the burner down on exactly the mornings you want it.