Ductless mini splits in Philomont.

About 85 percent of homes in ZIP 20132, the Purcellville-area ZIP that Philomont’s Census figures come from, are detached houses, and detached houses grow. A sunroom, a finished basement, a room over the garage: the original ductwork was drawn for the house as built, and an addition sits at the far end of it or off it entirely. One head on the wall, tied to an outdoor unit, lets that room run on its own settings. One room, one zone, $7,000 to $10,000 installed.

Age matters as much as additions. About 13 percent of homes in the ZIP area went up before 1960, and about 24 percent before 1980. A house from those decades may have ducts squeezed in long after it was built, or a house without any. Ductless avoids opening plaster and framing, since only a small line set crosses the wall. Two rooms are $11,000 to $15,000, three $12,500 to $18,000 and four $16,000 to $21,000, priced from the same book as the HVAC estimator.

Winter is where a mini split gets judged, since its outdoor half spends the cold months working in the open air. The Purcellville station averages a January low of 24.5F, counts 114.7 days a year with lows at or below 32F, and Philomont reached -2F on January 23, 2025. In a propane house, a head can carry the mild weather in a room. In an electric house, it can be the heat for an addition.

Plan the outdoor unit before the indoor head, since the line set between them crosses the wall. A unit on a pad with clearance for air and snow does better than one wedged against a wall. Western Loudoun took 30 to 36 inches in the January 2016 blizzard, and a mounting height above the drifts is worth the extra bracket.