An HRV is an effective way to ventilate a very “tight” (well-insulated) house experiencing high energy prices. A tight house collects more humidity and pollution than one with a lot of air infiltration. If a house has excess infiltration through leaky windows and a poorly insulated shell, air flow bypasses the heat exchanger, negating its work.

Though they are considered to be most effective in very cold climates, HRVs make sense where summers are hot, too. The actual economics indicate that HRVs may offer better energy savings in hot, air-conditioning climates.

Electicity needed for air conditioning is much more expensive than any other fuel, so every BTU you can recapture may have three times the value of the savings of heating fuels like natural gas. (A BTU measures the quantity of heat required to raise the temperature of 1 pound of water 1 degree Fahrenheit.) Of course, the higher the cost of energy, the more an HRV makes sense.

HRVs are practical for houses that have very high winter humidity, and enthalpy-type HRVs can assist air conditioning in climates where summer humidity is high. An HRV may also be a practical solution where there is a radon or formaldehyde pollution problem, though this should be determined by a qualified air quality expert.

In mild climates, exhaust-only ventilation may be a better solution than an HRV. Where outdoor winter temperatures are fairly high, there isn’t sufficient recoverable heat to repay the investment. And for cooling, the difference in temperature between indoor and outdoor air often isn’t high enough to justify the cost of installation, operation, and maintenance.