Todays Power Trip, Energy Efficient HRV Working?

Todays Power Trip, Is the Energy Efficient HRV Working Correctly?

by Don Ames

I was called today to check a duplex where the resident was concerned about mold in the bathroom.  So I gathered up some testing equipment and headed down the road. The duplex was constructed about 6 years earlier and had radiant floor heat.  Taking note on entering the unit, the indoor temperature was about 71 degree’s, the relative humidity was at 52%. The unit was very clean and I could tell that the resident’s took good care of the home. In the bathroom, I took note of a small amount of mold growing on the ceiling, about 3 square inches and some mold on the caulking that sealed the joint between the vinyl floor and the tub itself. Actually the bathroom looked very good and I had certainly seen alot worse mold conditions in many other bathrooms.

Well, as long as I’m there, might as well check out a few of the systems that should be working to keep mold at bay. First of all, the tub faucet was dripping and would not shut the water off completely, this provides moisture that can contribute to higher relative humidity. The ceiling fan was not making a sound, this is the first indication that the fan is not working. Yes, they do make some fans that are really quiet, but not that quiet. In this home, the ceiling fan is part of a HRV system - HRV stands for Heat Recovery Ventilator. This is a whole house ventilation system that brings in outside air, filters the air and dumps the air into the living room area through a register in the wall. At the same time the HRV is bringing in the outside air, it is exhausting inside air to the outside. While the HRV is doing it’s air-in-air-out routine, it is heating (or cooling) the air that enters the house by sending the air through a radiator that is heated (or cooled) by the air that is being exhausted.

In this home, the HRV is the ceiling exhaust fan and it is supposed to come on when the wall switch is flipped on. The HRV has a timer that allows the fan to operate for 30 minutes after the fan is switched off. So, turn the fan on, take a shower, turn the fan off and leave the bathroom and the fan turns itself off 30 minutes later. A good system for removing the mold causing moisture from the bathroom. That is – a good system if the darn thing will turn on.