In ZIP 20132, the Purcellville ZIP area Philomont sits in, about 85 percent of homes are detached houses, about one in nine are townhouses and about 7 percent are rented. A detached house puts the dryer wherever the family wanted it: a mudroom, a basement, a closet off the kitchen. That choice sets how far the lint has to travel. An outside-wall laundry has a short run. A dryer in the middle of the house can have a long, bendy one, and each bend is a shelf for lint.
The median owner home in that ZIP area dates to 2000, so a dryer vent cleaning is worth asking about in a house that has run a generation of laundry through one line. About 13 percent of homes went up before 1960 and about 24 percent before 1980. In a house that old the laundry may have moved since it was built, and a moved dryer often ends up with a longer run of pipe than the first spot had.
Winter is hard on the outside end. A spotter a mile southeast of Philomont measured 12.0 inches on February 21, 2015, and western Loudoun reported 30 to 36 inches in the January 2016 blizzard. A hood near the ground can end up buried, and a buried hood backs warm, damp air into the line, where lint cakes onto the walls. At the Purcellville station January lows average 24.5F.
Ashburn Volunteer Fire and Rescue, one of the companies in Loudoun County’s fire and rescue system, says to clean the dryer vent at least once a year, from the back of the dryer to the outside, and treats longer drying times as the sign of a clog. That is a fire company’s advice, not a rule for your address.