Furnace and AC replacement in Bristow.

Count the homes in 20136 by the decade they were finished and one bar towers over the rest: 5,558 of 9,619 from 2000 through 2009, against 2,023 from the 1990s and 348 from everything before 1990. In Linton Hall, the subdivisions’ Census place, the median owner home dates to 2004. Builders in those years set the furnace and the condenser during the same build, so a Bristow house still on its originals has two machines with identical mileage.

Two in three Linton Hall owner homes are detached, and a two-story single-family house of that vintage frequently carries a second system for the bedroom floor, its furnace or air handler up in the attic. Every system is quoted as its own line. If both are originals, get both measured on one visit, then decide which one goes this year and which waits.

On paper, the furnace is the half Prince William County cares about: gas furnace replacements always need a permit, while an outdoor unit traded for the same type on the same pad is exempt. So set the new condenser where the old one sat whenever the measurements allow. A new location pulls the county back in, and in Victory Lakes, 1,296 homes with 609 of them townhouses, the Covenants Committee reviews exterior changes before they happen.

The 1990s houses, a fifth of the ZIP, have likely replaced their first pair already, so their question is whether ducts drawn for 1995 equipment suit what goes in now. In houses of either age, a basement that got finished or a sunroom that got added is square footage the original sizing never saw, which is why we measure instead of trusting the size printed on equipment from 2004.