Quick answer
Whole-house ventilation runs continuously or on automatic intervals to dilute moisture and pollutants throughout the home, unlike bath and kitchen fans that run only when needed. The Building America Solution Center, a U.S. Department of Energy resource, describes three main approaches: exhaust-only (quiet fans pull air out; fresh air leaks in), supply (outdoor air is ducted in, often through the furnace or air handler) and balanced (an HRV or ERV brings air in and out through a heat exchanger). Exhaust-only is cheapest and simplest; balanced HRV/ERV costs more but recovers heat and controls where air comes from. The right choice depends on your climate, how airtight the house is and your existing ductwork.
Why whole-house ventilation?
Older homes often get fresh air by accident, through gaps and cracks. As homes are sealed and insulated, that accidental airflow drops, and moisture, odors and pollutants from daily life can build up. Local exhaust fans in kitchens and bathrooms remove contaminants near the source when they run. Whole-house ventilation, as the Building America Solution Center explains, is intended to operate continuously or at automated intervals to dilute potential contaminants across the whole house.
ASHRAE Standard 62.2 sets minimum requirements for adequate home ventilation, and many codes and programs reference it. In existing homes, the Building America Solution Center notes that adding whole-house ventilation is often more involved and costly than in new construction.
The main options compared
| System | How it works | Main advantages | Main drawbacks |
|---|---|---|---|
| Exhaust-only | Kitchen, bath or laundry fans exhaust air continuously or on timers; replacement air leaks in through the envelope or passive vents | Low cost; easy to install and test; very little energy; quiet; reliable | May depressurize the home; no energy recovery; incoming air comes from unknown gaps, unfiltered |
| Supply (including central fan-integrated supply, CFIS) | Outdoor air is ducted to the return side of the central air handler, filtered, heated or cooled and distributed | Air drawn from a known location; filtered and tempered by the HVAC system | Can cause comfort issues in very cold or very hot, humid weather; harder to commission |
| Balanced HRV | Brings air in and exhausts air at the same time through a heat exchanger | Recovers heat; distributes fresh air; doesn’t create large pressure differences | Higher cost; filter maintenance; can be hard to install; possible noise |
| Balanced ERV | Like an HRV, but transfers moisture as well as heat | Same as HRV, plus moisture transfer | Same as HRV |
Exhaust-only: the simplest start
Most homes already have bathroom fans, so upgrading one to a quiet, efficient model that runs continuously at a set rate is often the easiest path. The Building America Solution Center notes these fans use very little energy, 5 to 12 watts for 50 to 80 cfm, and that exhaust-only ventilation works well in cold, dry climates, where outdoor air is generally drier than indoor air.
Watch out: exhaust-only systems may depressurize the home. If you have fuel-burning appliances that rely on natural draft (such as an older furnace, water heater or fireplace), have a qualified contractor check that adding continuous exhaust won’t interfere with their venting. The Building America Solution Center also advises caution with exhaust-only in humid climates.
Supply ventilation: using your ducts
In homes with forced-air heating and cooling, central fan-integrated supply (CFIS) draws outdoor air through a filtered intake into the air handler. The Building America Solution Center notes this can help in humid climates when indoor air is drier than outdoor air, because the house is slightly pressurized, but that it’s a poor strategy in cold, dry climates where indoor air is more humid than outdoor air. It also warns that indoor humidity can rise in shoulder seasons when the air conditioner runs little, increasing the need for supplemental dehumidification.
Balanced ventilation: HRV and ERV
A heat recovery ventilator (HRV) runs outgoing and incoming air through a heat exchanger, warming incoming air in winter and cooling it in summer. An energy recovery ventilator (ERV) does the same but also transfers moisture. Both can connect to the central air handler and ducts or be ducted independently. They give the most control over where air comes from and goes, at a higher price and with regular filter maintenance.
HRV or ERV? The practical difference is moisture: an HRV exchanges only heat, while an ERV also moves some moisture between the two air streams. Which one suits a home depends on the climate and on whether the house tends to be too humid or too dry indoors. Ask the designer to choose and size the unit for your climate and house, and to explain how it will handle humidity in each season.
How to choose
Decision checklist
- Climate: cold and dry favors exhaust-only or balanced; hot and humid calls for caution with exhaust-only and attention to dehumidification.
- Airtightness: the tighter the house, the more a planned ventilation system matters.
- Existing ducts: forced-air systems make supply or ducted HRV/ERV easier; homes without ducts often start with exhaust fans or ductless units.
- Combustion appliances: check how depressurization could affect them.
- Budget and upkeep: exhaust-only is cheapest to install and run; HRV/ERV cost more and need filter changes.
- Code: ask whether ASHRAE 62.2 applies to your project.
Worked example: running cost of exhaust-only
Assumed values: a continuous bath fan drawing 10 W (within the 5–12 W range the Building America Solution Center cites for 50–80 cfm), running all year, at 18.31 cents per kWh (EIA U.S. average residential price, July 2026).
- Energy: 10 W × 8,760 hours ÷ 1,000 = 87.6 kWh per year.
- Electricity cost: 87.6 × $0.1831 ≈ $16 per year.
- Not included: the heating or cooling of the outdoor air that replaces the exhausted air, which depends on climate and flow rate.
Illustrative example with an assumed fan wattage.
Whatever system you choose, the Building America Solution Center emphasizes installing and commissioning it so that it actually delivers the design airflow; a system that isn’t tested may move far less air than intended.
Frequently asked questions
Do I need whole-house ventilation if I have bathroom fans?
Bathroom fans handle local moisture. In a fairly airtight home, a planned whole-house system, which can be as simple as a continuously running quiet bath fan, keeps the rest of the house ventilated.
What’s the difference between an HRV and an ERV?
Both exchange heat between outgoing and incoming air. An ERV also transfers moisture; an HRV transfers only heat.
Is exhaust-only ventilation bad?
No. It’s low-cost and reliable and works well in cold, dry climates. Its limits are depressurization, no heat recovery and uncontrolled air inlets.
Will more ventilation lower humidity?
When outdoor air is drier than indoor air, yes. In humid weather, ventilation can add moisture, which is why the system choice depends on climate.
Sources
- Building America Solution Center (U.S. DOE / PNNL). Whole House Ventilation Strategies for Existing Homes.
- Building America Solution Center. Whole-House Ventilation Strategies for New Homes: pros and cons, climate notes, fan wattage.
- U.S. Energy Information Administration. Electric Power Monthly, Table 5.6.A.
Next step
