Which Parts of a Ventilation System Collect Dust
| Part | What builds up | Cleaning |
|---|---|---|
| Bathroom fan grille and blades | Dust and lint, damp from showers | Wash the grille; vacuum blades with power off. See bath fan cleaning |
| Kitchen hood filters and duct | Grease | Degrease filters; a professional for a greasy duct. See range hood duct cleaning |
| Fresh-air intake hood | Leaves, pollen, insects | Clear it from outside |
| ERV or HRV filters | Dust from incoming and outgoing air | Clean or replace per the manual |
| ERV or HRV core | Fine dust on the exchange surfaces | Per the manual only |
| Outdoor exhaust hoods | Lint, nests, stuck dampers | Check that each damper swings freely |
Exhaust Airflow Minimums in Virginia Homes
Section M1505.4.4 of the 2021 Virginia Residential Code sets minimum local exhaust rates.
| Room | Intermittent | Continuous |
|---|---|---|
| Kitchen | 100 cfm | 25 cfm |
| Bathroom or toilet room | 50 cfm | 20 cfm |
A fan rated at those numbers delivers less once dust coats its grille and blades or its outdoor damper sticks. Bathroom exhaust also has to go directly outdoors, never into the attic (Section M1505.2); the attic ductwork page lists the other exhausts with the same rule.
Cleaning an ERV or HRV Core
Start With the Manual
Models differ. The manufacturer's manual gives the filter and core cleaning directions.
Turn the Unit Off
Switch it off, and unplug it if the manual says to.
Check the Filters
Vacuum, wash or replace them as directed.
Treat the Core as the Manual Directs
Some cores rinse clean. Many ERV cores don't tolerate water, so never guess.
Clear the Outdoor Hoods
Leaves and debris on the intake starve the unit of fresh air.
ERV or HRV: What Your Unit Does
Both units swap stale indoor air for fresh outdoor air and pass the two streams through a heat exchanger, so less of the heating or cooling you paid for leaves with the stale air. The difference is moisture. An HRV transfers heat only. An ERV also transfers some water vapor, which the Department of Energy notes keeps indoor humidity steadier.
| Feature | HRV | ERV |
|---|---|---|
| Transfers heat | Yes | Yes |
| Transfers moisture | No | Yes, some |
| Core cleaning | Per the manual; some rinse clean | Per the manual; many cores can't take water |
Check the label on the unit before cleaning. Washing an ERV core that isn't rated for water can ruin the part that does the moisture transfer.
Makeup Air for Big Range Hoods
A powerful kitchen hood pulls a lot of air out of a tight house, and that air has to be replaced. Virginia's residential code requires makeup air for kitchen exhaust hood systems rated above 400 cfm. If a hood that size was added without makeup air, bring it up with an HVAC contractor.
Is Cleaning a Ventilation System Worth It?
For any part with visible buildup, yes. A bath fan that barely moves air leaves shower moisture behind, and the EPA's mold guide ties mold growth to moisture and advises keeping humidity below 60 percent. Grilles and filters are quick homeowner jobs; greasy kitchen ducts and ERV or HRV service are better left to a technician.
What You Can Clean and What to Book
Most of a ventilation system is homeowner work that costs nothing but time. The paid part is the ductwork you cannot see, and the short list below separates the two.
| Part | Who |
|---|---|
| Fan grilles and blades | You |
| ERV or HRV filters and core | You, following the manual |
| Outdoor intake and exhaust hoods | You, where reachable from the ground |
| Exhaust ducts through the attic or roof | Technician |
| Dryer vent line | Technician, $135–$360 around Dulles |
If a fan still fails the tissue test after cleaning, the problem is in the duct or damper, and that is where a visit earns its cost.
Northern Virginia market ranges reviewed in 2026, not a quote. Your price depends on vent count, system count and access.