Whole-home humidifiers in Catharpin.

Catharpin is a few hundred owner homes, all detached, and the Census margin on them is wide, so take the shares as rough. They still tell a clear story. A fifth of the houses predate 1960, four in ten predate 1980, and most of the rest were built on acreage in the eighties, nineties and after. Country houses here tend to grow: a family room added in 1994, a garage turned into an office.

Each addition is another place for dry air to hide. A room built onto an older house often has its own duct branch, or its own small heat pump, and gets less air than the main house. A humidifier on the main system humidifies what that system reaches. We walk the house first and ask which rooms feel driest, and that tells us whether one unit covers it.

Heating is nearly half electric and a third propane. Heat pump homes get the fan-powered Aprilaire, since cool supply air cannot carry vapor to a bypass unit. A propane furnace makes warm air like a gas one, and the bypass works. Only about one home in fourteen is on gas, so the usual city assumption about gas furnaces does not apply here.

Propane customers know the feeling of a long, cold stretch. The furnace runs more, the air dries further, and the static gets sharp by the second week. A humidifier is the answer when your hands crackle on the doorknob. The whole-home humidifier page has the models, and the $99 visit sorts out one that stopped.