Here at GBA, we have consistently advised readers who plan to install a heat-recovery ventilator (HRV) or an energy-recovery ventilator (ERV) to install dedicated ventilation ductwork rather than trying to distribute ventilation air through their heating and cooling ducts. That advice won’t seem particularly burdensome if your house doesn’t have any heating and cooling ducts — as is typical in a home with ductless minisplits or a hydronic heating system and no central air conditioning.
But if your house already has heating and cooling ducts, you may instinctively rebel at GBA’s advice, muttering, “Why can’t I use the ducts that I’ve already got?”
Here are the reasons:
In the past, I often endorsed the use of exhaust-only ventilation systems in small homes with simple floor plans. Increasingly, however, I’ve become convinced that we need to pay better attention to indoor air quality, especially in bedrooms. It turns out that bedrooms in homes with exhaust-only ventilation systems usually don’t get enough fresh air. So anyone who cares about bedroom air quality probably needs an HRV or ERV with dedicated ventilation ductwork.
If your HRV has dedicated ventilation ductwork — a type of ventilation system that is sometimes called a “fully ducted” system — the HRV will usually deliver fresh air to the living room and bedrooms, while simultaneously exhausting stale air from bathrooms (and sometimes from the laundry room or kitchen). With fully ducted systems, fresh air delivery and stale air extraction happen in the rooms where the system designer intends these events to occur. These systems use less energy than systems connected to heating or cooling ductwork, and they are far easier to commission and balance.
If you intend to pull stale air from your kitchen, remember that a range hood should never be connected to…