We are often asked, "Should I use an HRV or an ERV?" Building professionals sometimes assume that the use of an HRV versus an ERV can be determined by geography, but it’s often not that simple. Much of the country uses an HRV and one could generalize that ERVs are better for humid climates, but what about those climates that are both dry and humid during the year?
For New England, often building professionals use an HRV, but one could realistically use an ERV during humid summer months and an HRV during dry winters. Also, it can depend on the number of people in the house, how much humidity is in a particular home, and other individual elements. One very important driver is occupancy/density in homes. A modest home with one or two occupants provides much less internal moisture than the same home with four occupants, two dogs and a cat. The low occupancy home may want to retain moisture by using an ERV, while the higher occupancy home may want to use an HRV due to higher levels of moisture from high occupancy. The Passive House Institute in Germany has been focusing on refining guidance to prevent overventilation and optimize moisture management.
Some HRVs/ERVs have a removable core so that the best option can be used for the best time of year. In climates where either can be used, it’s often recommended to use an HRV because of the higher efficiency. Zehnder makes recommendations on a case by case basis.