Thanks to Alan Carson for the good info on HRV's.
The article did not cover what I find to be the single most common concern on the HRV's we inspect in Minnesota. Over three fourths of all HRV's we check
have clogged air intakes as shown in the attached photo.
Many of our cities and towns are near water and many Cottonwood trees. The fuzzy seeds from these trees float in the air for several weeks in the summer
and clog the air intake screens. Unfortunately the HRV maintenance instructions are posted INSIDE most of the HRV's, so home owners typically are not aware
that they need to check and clean the intake screen.
Our practice is to clean HRV air intakes when clogged, and show the prospective buyer this procedure.
When doing a radon test with the inspection, it is important to have the HRV intake clean so that the unit is operating with balanced intake and exhaust
flows. Operating as an exhaust only device (clogged intake) could adversely influence the radon test.
I hope you can post this info as an update to Alan's good work.
Roger Hankey, ASHI Certified Inspector
First ASHI® Member in Minnesota, ASHI #269