Heat Recovery Ventilators (HRV’s)

It may not look like it but the screened portion of this HRV intake just behind the white louvers is caked solid.

Heat Recovery Ventilators (HRV’s) are wonderful devices. They do improve indoor air quality within the home by continuously exchanging stale indoor with fresh outdoor air. Most effective in the heating season, the warm indoor air partially heats the incoming cooler air. This is the heat recovery portion of its function.

I’m a firm believer in their use, particularly in newer well sealed and better insulated buildings  In my experience inspecting homes however, I do see many problems with them. Some of the issues are due to their incorrect installation, which is the topic of another post. Many though, if not most of the problems are due to inadequate maintenance.

There are filters and a diamond-shaped heat recovery core inside the unit that should be cleaned regularly. A good online guide to the care and use of HRV’s is here. One little often neglected but very important part their maintenance is the outside air intake grill.

There typically will be two rectangular louvered-type vents terminals on the outside wall of the house  somewhere near where the main box is inside the basement. One vent blows stale air out and the other brings fresh air in to the HRV. I see time and time again that the air intake grill is caked solid with grass clippings, dog hair, and other outdoor particulates.

This can drastically reduce or block off the air flow into the unit thus negating about half the benefit of the system. Use a shop vac and maybe a soapy brush and water to clean the outside intake grill along with the other inside maintenance and you will have well-functioning HRV.