UPDATED on June 29, 2017, with information on Aldes constant airflow regulators.
A balanced ventilation system — for example, a system with a heat-recovery ventilator (HRV) or an energy-recovery ventilator (ERV) — exhausts stale air from some rooms in a building, while simultaneously introducing fresh outdoor air to other rooms. The best balanced ventilation systems use dedicated ventilation ductwork. Usually, these systems pull exhaust air from damp, smelly rooms — bathrooms and laundry rooms — and introduce fresh air to the rooms where people spend most of their time — bedrooms and the living room.
Some of these balanced ventilation systems operate at a low speed for 24 hours a day. Others have timers that operate the fans for a certain number of minutes — perhaps 20 or 40 minutes — per hour. These controls aim to ventilate the house at a pre-determined rate — for example, the rate recommended by the ASHRAE 62.2 standard. Depending on whether you use the old ASHRAE formula or the new ASHRAE formula, and depending on the size of the house and the number of occupants, a single-family house might require anywhere from 45 cfm to 120 cfm of ventilation air.
Many HRV manufacturers advise builders that the exhaust function of an HRV is adequate for removing moisture and odors from bathrooms. However, a few HRV manufacturers and some builders provide different advice; they advise that even when a bathroom has an exhaust grille connected to HRV ductwork, it’s still important for every such bathroom to have a separate bath exhaust fan.
Which approach makes the most sense?
Venmar Ventilation is a manufacturer of HRVs with headquarters in Quebec. According to specialists at Venmar, it’s perfectly possible to use an HRV system as the only method of exhausting air from a bathroom.
John Pothier, a technical specialist at Venmar, told me that most Canadian homes take that approach.…