Three hard freezes a year, and a furnace that spends summer rusting: how to choose

The climate writes the spec

Jacksonville’s winter asks very little of a furnace. The 1991-to-2020 normals put about 14 freeze nights a year on the calendar, three of them hard freezes at 26 degrees or below, with the first typically in early December. Normal winter lows sit in the mid-40s. A furnace here runs for a cluster of mornings and the occasional cold evening, perhaps 150 to 250 hours in a typical year.

Jacksonville’s summer asks a great deal of the same furnace while it sits. From June through August the dew point averages 71 to 73 degrees. A furnace in a Riverside hall closet, a San Marco utility room or an Ortega garage sits in that air for eight months. Burner compartments rust. Flame sensors oxidize. Igniters grow brittle. Inducer housings fill with mud dauber nests. The heat exchanger, if the airflow has been low for years because the return was never enlarged, has thinned and cracked without anyone noticing.

That combination, a short heating load and a long humid idle, is why Jacksonville furnaces are replaced for corrosion and cracked exchangers far more often than worn burners, and why the first question here is whether the house should get a furnace at all.

The furnace decision tree, top to bottom

Start at the top. Each answer leads somewhere specific.

Does the house have natural gas service? TECO Peoples Gas serves much of the historic core: Riverside, Avondale, Ortega, San Marco, Springfield, Murray Hill and parts of the Westside. If yes, continue. If no, a gas furnace means a propane tank, common in Baker and Nassau along US 90 and US 301, or the furnace question becomes a heat pump question.

Is the existing furnace under about 12 years old with a single failed part? Repair it. Even an inducer motor or a gas valve is sensible on a young furnace. Skip to the bottom.

Is the heat exchanger cracked, or is the cabinet rusted through? Replace. A cracked exchanger is a carbon monoxide risk, and no repair addresses general corrosion.

Does the house also need a new air conditioner or heat pump within a few years? If yes, consider a dual-fuel system: a heat pump carries the mild mornings in the 40s and 50s at a fraction of the gas cost, and the furnace takes over only on the hard freezes. For a large Ortega or San Marco house with gas already there, this is usually the most efficient answer in Jacksonville.

Is the existing heat electric strips in an air handler, as in many Arlington and Westside ranches? Then the replacement is a heat pump, not a furnace. The strips stay as backup.

Is there no gas and no propane, and a modest house? A heat pump, sized by load calculation. JEA has offered a $200 Heating & Cooling rebate on qualifying ENERGY STAR heat pumps meeting its Tier 1 thresholds, applied on the contractor’s invoice; the 2026 cycle closed October 10, 2026; ask whether the next has opened. [[CONFIRM WITH JERRY]]

Still a furnace after all that? Then size it by load calculation, not the old nameplate, correct the return while the closet is open, and choose a two-stage or variable-capacity model that runs long and low on a 40-degree morning.

Request a heating replacement estimate

Gas, propane, oil and electric: what we install and what we service

Cook’s is a Lennox dealer and installs Lennox gas furnaces, including two-stage and variable-capacity models that pair with Lennox heat pumps for dual-fuel. For repair and maintenance we service Lennox, Carrier, Bryant, Trane and every other brand, including the oil furnaces still found in a few older Ortega and Fernandina Beach homes and the electric furnaces in manufactured homes across Baker and Nassau. Want a different furnace brand on a new install? Raise it at the quote.

Five warranty facts for a Jacksonville furnace

• Heat exchanger warranties are long, often twenty years or lifetime, and they cover the exchanger itself, not the labor to replace it. Ask what the labor side looks like and get Cook’s labor coverage on a furnace install in writing. [[CONFIRM WITH JERRY]]
• Registration within the manufacturer’s window unlocks the extended parts warranty. We register the equipment for you.
• Airflow is a warranty condition. A furnace installed on an undersized return can run hot enough to crack its exchanger, and a manufacturer can decline the claim. Correcting the return is not an upsell in a 1920s Avondale house; it is what keeps the warranty intact.
• Annual service is commonly required. The fall maintenance visit creates the record.
• Satisfaction guaranteed on the install itself.

Financing, credits and what no longer applies

Financing with low monthly payments is available on new high-efficiency systems and is quoted in writing, with lender, rate and term stated plainly; none appear here because they change. The federal 25C tax credit that once applied to high-efficiency furnaces ended December 31, 2025. Ask whether any utility rebate applies to gas furnaces specifically; the JEA rebate applies to heat pumps, which is one more reason a dual-fuel or heat pump quote sits beside the furnace quote. [[CONFIRM WITH JERRY]]

What install day looks like in a hall closet

Floors protected, gas and power off, old furnace out, flue inspected and corrected, return enlarged if the measurements called for it, new furnace set and leveled, gas piping pressure tested, condensate drain trapped on condensing models, thermostat staged, and a full heating cycle run with combustion analyzed and temperature rise recorded. Permit and inspection are ours. The truck comes from the Palm Coast headquarters, about 74 minutes down I-95, on whatever day and hour you need.