Herndon Homes Compared With Fairfax County
Herndon sits in Fairfax County, Virginia. The table shows how its housing differs from the county as a whole, which decides what a duct and dryer vent visit checks first.
| Measure | Herndon | Fairfax County |
|---|---|---|
| Median year built | 1983 | 1983 |
| Built in the 1970s or 1980s | 56% | 42% |
| Detached houses | 44% | 46% |
| Townhomes | 27% | 23% |
| Apartments and condos | 29% | 31% |
| Heat with electricity | 60% | 42% |
| Owner-occupied | 62% | 69% |
Source: U.S. Census Bureau, American Community Survey 2024 5-year estimates. Figures are estimates and are rounded.
Town of Herndon or Just a Herndon Address?
The Town of Herndon covers about 4.2 square miles in Fairfax County. The Herndon mailing name reaches much further: homes in Franklin Farm and McNair also carry Herndon addresses in ZIP 20171, yet they sit outside the town in unincorporated Fairfax County. A sliver of the town, just over two acres, technically lies in Loudoun County.
The county matters for permits and for the code rules a contractor follows, so give your street address and ZIP code when you ask for an estimate. If you live south of the Dulles Toll Road, the Franklin Farm page describes your housing more closely.
Electric Heat in 1970s and 1980s Houses
Six in ten Herndon homes heat with electricity, well above the Fairfax County share of 42 percent. A heat pump moves air through the ducts for long stretches in both winter and summer, so the filter loads faster and leaks in the ductwork cost more over a year.
| Built | Share of homes | First thing to check |
|---|---|---|
| Before 1970 | 12% | Duct materials and insulation before any cleaning |
| 1970s | 31% | Original joints and tape; duct sealing |
| 1980s | 25% | Leaks at boots and the air handler; filter fit |
| 1990 and later | 32% | Dust load and the dryer vent run |
ENERGY STAR estimates that a typical house loses 20 to 30 percent of the air moving through its ducts to leaks. In a 40-year-old system, sealing those leaks often does more than cleaning; the duct sealing page covers the methods and materials.
Before Cleaning a Pre-1980 System
About four in ten Herndon homes predate 1980. Before cleaning an older heating system, the EPA advises checking its materials for asbestos, and duct insulation that is wet or moldy gets replaced rather than cleaned. A camera inspection settles both questions before any brush goes into the ducts.
Dryer Vents in Herndon Townhomes
Townhomes make up 27 percent of Herndon's housing. Their dryers often sit on an upper floor or in the middle of the unit, so the exhaust travels a long path to a side wall or the roof. Virginia's residential code limits a dryer exhaust run to 35 feet, minus an allowance for each elbow. Cleaning typically costs $135 to $360, with roof terminations at the upper end; the dryer vent cleaning page lists the warning signs.
Herndon Duct and Dryer Vent FAQs
Is Herndon in Fairfax County or Loudoun County?
Herndon is a town in Fairfax County. Just over two acres of the town technically lie in Loudoun County, and some homes with a Herndon mailing address sit outside the town in unincorporated Fairfax County.
How much does air duct cleaning cost in Herndon, VA?
Whole-system air duct cleaning in Herndon follows the Northern Virginia range of about $500 to $800 per system. Townhomes and condos usually run $190 to $650, and dryer vent cleaning runs $135 to $360.
Do you serve Herndon 20171 addresses outside the town?
Yes. Herndon 20171 addresses in Franklin Farm, McNair and the rest of the Oak Hill area are covered, along with the town itself in ZIP 20170.
Is duct cleaning different with a heat pump?
The ducts, blower and coil are cleaned the same way. A heat pump runs the blower for long stretches in both seasons, so the filter needs changing more often and duct leaks cost more over a year.