Every home (new and old) needs some form of mechanical ventilation in order to bring in fresh air from outside, to remove stale air from inside, and to provide some level of moisture control. In fact it is now mandatory for all new home construction to have a mechanical ventilation system installed to satisfy this necessary requirement. The Heat Recovery Ventilation, or Heat recovery ventilator, is one such mechanical ventilation system that is seen in newer and recently updated homes.
As shown in the diagram, the Heat recovery ventilator works by bringing in fresh outdoor air, drawing it through its internal cross-flow heat exchanger core where it is heated by the stale outgoing air. The Heat recovery ventilator then distributes this fresh air throughout the property by ductwork installed especially for the Heat recovery ventilator, or sometimes through the forced-air system ductwork. A good analogy would be to think of the Heat recovery ventilator like the lungs of the home; in the sense the unit takes in fresh outdoor air to distribution throughout, home, while at the same time exhausting or expelling stale indoor air. As such, a properly maintained Heat recovery ventilator can significantly improve indoor air quality (IAQ) by expelling humidity, carbon dioxide (CO2), cooking odours, dust/allergens, VOC’s and even animal dander /odours from the inside of the home and replacing this stale air with a fresh supply from outside the building.
As a Registered Home Inspector, the most frequent issues seen during a typical home inspection as it relates to the Heat recovery ventilator system are a serious lack of maintenance and/or cleaning of these units. Sadly, most homeowners really do not understand how the Heat recovery ventilator system works or how often it should be cleaned and serviced.
Since we know we must bring fresh air into the property, it is also extremely important to understand where this fresh air is coming from. I’ve seen fresh air vents that are under decks with limited accessibility. Sadly, these vents are usually quite dirty, blocked and/or covered with mould growth. Additionally, the space under most decks is usually damp and musty, with decaying organic material (i.e. leaves and /or other plant material) and sometimes even animal feces. Is this really the type of fresh air anyone would really want to bring into their home?