Boiler repair and replacement in Sterling.

The Census counts 21,254 owner homes in Sterling, and more than half went up between 1980 and 1999, the typical one in 1979. Gas heats close to six in ten and electricity about four in ten. Most of those houses were built with ducts and a furnace, so a hot water boiler in Sterling is the exception, and the company you call should know it’s a different machine.

Gas coverage varies by neighborhood: it’s high in Oak Grove, Cascades and Lowes Island, splits roughly down the middle with electric heat in Sugarland Run and around Sterling Park, and runs low in Countryside, where heat pumps do most of the work. Propane barely registers, so a Sterling boiler is almost certainly on natural gas.

A boiler original to a Sterling house from the late 1970s has carried it for a long time, and when its heat exchanger is the problem, replacing it is the honest answer. From there you pick the vent: keep the chimney with another cast iron boiler, or hang a condensing one on the wall for $12,782 to $16,500 installed and run its exhaust out the side of the house. About 35 percent of owner homes are townhouses, where the boiler shares a closet with the water heater and a combi that also makes the hot water frees the space.

Dulles Airport, next to Sterling, counts about 102 nights a year at or below freezing and about five at 10 degrees or colder, against about 60 freezing nights at Reagan National. Loudoun’s fire and rescue system wants heating equipment and chimneys cleaned and inspected every year, and its fall clock-change reminder asks for a CO alarm outside each sleeping area and on each level.