Air duct cleaning in Delaplane.

Delaplane is heating country first. The nearest long-record NOAA station, Warrenton 3 SE, about 18 miles south-southeast, counts more than four heating degree days for every cooling degree day, and January nights there average just under 25 degrees. So the blower in a Delaplane house does most of its yearly running between November and March, pulling the house’s air back through the returns night after night. The ridge runs colder: Mount Weather, a station on the Blue Ridge 10 miles north at 1,659 feet, logs about 5,300 heating degree days to the valley station’s 4,700, and a house partway up the slope sits somewhere between the two.

What that air travels through depends on the fuel. About half of Delaplane’s owner homes burn propane, and the Census counts no owner home in 20144 heating with natural gas. A propane furnace usually carries the air conditioner’s coil on top of it, so one blower and one set of ducts serve both seasons. About three owners in ten heat with electricity, which here usually means a heat pump with its air handler in the basement, the attic or a closet. Either way our tech starts the camera at the return, the side every winter’s air comes back through.

The houses split two ways. Four homes in ten across the ZIP went up in the 1990s, and the typical owner’s house dates from 1986, so a lot of Delaplane ductwork is past thirty and has outlived at least one furnace or heat pump. The older group is the valley’s farm dwellings, many built from fieldstone cleared out of the fields, where the ducts were threaded in long after the walls went up: through a closet, along a later wing, across a crawlspace. Those runs bend more, and the camera has more corners to look around.

Country houses put a few more things in the returns. About one owner in twenty heats with wood, and ash from a stove or an insert settles wherever the return can reach it. And the state’s 2004 survey of the Crooked Run Valley, which takes in Delaplane, found a large share of the valley’s newer houses lived in only on weekends or by season. A house shut up for weeks can collect what a lived-in one doesn’t, insects at the registers and now and then a mouse in a crawlspace run, and all of it shows up on the photos.