What Is an ERV? Filtered Fresh Air for Your Home

An ERV, or energy recovery ventilator, is a quiet, whole-house system that brings in fresh, filtered outdoor air and sends stale indoor air out, while keeping most of the heat and humidity you’ve already paid for. It is how a well-sealed home “breathes” on purpose, instead of through leaks.

The two airstreams pass each other inside the unit without mixing. In winter, the outgoing warm air warms the incoming fresh air. In summer, the process reverses.

Why a modern home needs one

Older homes get fresh air by accident, through gaps in walls, floors and windows. That air is unfiltered and uncontrolled. Once a home is sealed with a high-performance envelope, those leaks are gone, so fresh air has to be supplied deliberately.

The U.S. Department of Energy notes that many homes lack whole-house fresh air systems that dilute moisture, dust, pollen and particulates, and that these contaminants can trigger asthma and allergy attacks. A balanced system like an ERV dilutes them while saving energy.

What an ERV does for your home

• Fresh air in every room, all the time, not only when a window is open.
• Filtration on the way in. Incoming air passes through a filter before it reaches you. Higher-rated filters, such as MERV 13, capture more of the fine particles in pollen, dust and smoke.
• Stale air out. Cooking odors, moisture and indoor pollutants are exhausted continuously.
• Steadier humidity. Unlike a heat recovery ventilator (HRV), an ERV also transfers some moisture, which helps keep indoor humidity more constant.
• Energy recovery: most ERVs recover about 70–80% of the energy in the outgoing air. In a mild climate like ours the savings are modest; the main benefit is fresh, filtered air.

ERV vs HRV

Both bring in fresh air and recover heat. The difference is moisture: an ERV transfers some water vapor between the airstreams and an HRV transfers only heat. In the Peninsula’s mild, often dry climate, an ERV is a common choice, but the right system depends on the house.

ERVs and wildfire smoke

During smoke events, a filtered fresh-air system is far better than leaky walls letting smoke in. Many systems can also be turned down or switched to recirculate when outdoor air is very poor. Related: What makes a home smoke-ready.

Maintenance

An ERV needs little attention: filters changed on a schedule and the core cleaned periodically, as the manufacturer recommends.

FAQ

Is an ERV the same as air conditioning?
No. An ERV supplies fresh air and recovers energy. Heating and cooling come from a separate system, such as a heat pump.

Will I notice it running?
A properly sized and installed ERV runs quietly in the background.

Can an ERV be added to an existing home?
Yes, but it works best with a sealed envelope and dedicated ducts, which is easiest during a remodel or rebuild.

Does an ERV filter out pollen and smoke?
The filter on the incoming air captures particles. How much depends on the filter rating used.

Want filtered fresh air throughout your home? Start the conversation

Part 3 of 7 in Healthy by Design, our Wellness series in the Journal. Next: What Makes a Home Smoke-Ready? See how Greenberg builds for wellness.

Sources: U.S. Department of Energy, Whole-House Ventilation