Whole-home humidifiers in Casanova.

Casanova’s own ZIP is boxes only, so the Census figures here are for the Catlett ZIP, 20119, around it. Every owner home in that area is a detached house, and the median went up in 1990. That’s single houses on acreage with one furnace or air handler for the whole place, and no shared walls to think about. That keeps the install simple: the water usually comes from a basement or crawlspace line within a few steps of the equipment, and the drain has an easy path out.

Electricity heats about half of owners and propane about three in ten. A heat pump house wants the fan-powered kind, since its air is too mild to carry a bypass unit. A propane furnace blows hot enough for bypass. Where a furnace backs up a heat pump and takes over on the coldest nights, we ask which runs more and mount the unit there.

About one owner home in eight heats with wood or another fuel, a bigger slice than most of our towns. Where a stove carries the living room and the ducts barely reach the back bedrooms, a whole-home unit works on the rooms with ducts, not the one by the fire. Worth a talk before anyone signs. Ask the installer to point at each register you use and tell you what’s feeding it.

A bit under one in six homes predates 1960, frame farmhouses that give up air through the sills all winter. Single-pane glass on a north wall is where you’ll meet a humidifier’s limit first, as a film of water on the window. Drop the setting a few points on the coldest nights and the glass clears. A humidity gauge on the wall, the kind that costs a few dollars, will show you in a day or two where you stand.