Furnace tune-ups in Calverton.

Warrenton 3 SE, the long-record weather station six miles west-northwest of Calverton, averages a January low just under 25 degrees and about 98 nights a year at or below freezing. Fauquier County’s building criteria put the winter design temperature at 17 degrees, the cold night a heating system is sized for. Colder ones come: about five a year at 10 or below, a 3 degree morning there in January 2014, and wind chills to ten below across southern Fauquier in late January 2026.

In Catlett’s 20119, the ZIP most Calverton houses share, about half the owner homes heat with electricity, usually a heat pump with electric strips behind it. A heat pump loses output as the air gets colder, so on a 17 degree night the strips carry part of the house, and on a 3 degree one most of it. The fall visit runs it in heating and checks the strips and the defrost, at the same $69 a system as a furnace.

About three owner homes in ten burn propane, and the Census finds none here on natural gas. Many propane furnaces in houses from the 1990s on are high-efficiency ones that breathe in and exhaust through two plastic pipes in a side wall, sometimes low to the ground. On January 23, 2016, the Warrenton 3 SE station logged 20.5 inches of new snow, with 25 on the ground three days later. Drifts like that can bury those pipes, and the furnace shuts itself down when they do; the tune-up tests the switch that makes it.

About one owner home in eight lists wood or another fuel as its main heat. Many of those houses keep a heat pump or propane furnace as backup, and a backup can sit idle through a mild spell, then get called on the night the stove burns down. Light it in October, with somebody watching.