Powerful kitchen exhaust fans do a good job of removing cooking odors and smoke. They also have the potential to depressurize a house, causing water heaters to backdraft and pulling ashes out of the fireplace and onto the hearth.

Our ‘question of the week’ comes from Kevin, who explains that he will be installing a 600-cfm downdraft exhaust fan in the kitchen of a new Passivhaus residence. "Our HRV(HRV). Balanced ventilation system in which most of the heat from outgoing exhaust air is transferred to incoming fresh air via an air-to-air heat exchanger; a similar device, an energy-recovery ventilator, also transfers water vapor. HRVs recover 50% to 80% of the heat in exhausted air. In hot climates, the function is reversed so that the cooler inside air reduces the temperature of the incoming hot air. installer said that he has heard of people tying in their cooktop ventilation to their HRVs," Kevin wrote. "However, I am concerned that this would invalidate the warranty and greatly shorten the lifespan of the unit."

John Brooks warned Kevin that the stovetop exhaust fan should not be tied in to an HRV.

Andrew Henry suggested ventilating the kitchen differently — through a ceiling grille located a suitable distance away from the range.

Martin Holladay explained that a house with a 600-cfm downdraft exhaust fan needs a makeup air unit.

Derek Vander Hoop noted that in Passivhaus building, the "perfect solution" is to connect the downdraft fan to a grease filter rather than exhausting the air directly outdoors. An HRV can then handle the moisture and odors.

Robert Riversong advised that gas stoves should always be vented to the outdoors.

What do you think?
Should an energy-efficient home include a powerful exhaust fan?
Must cooking odors always be vented outdoors?
Should an HRV pull air from a kitchen?

Read Kevin's original question, and all of the responses it generated, here.

If you're interested in more information, check out these resources:
"HVAC Equipment Can Overpower Wind and Stack Effect"
"Exhaust Ventilation"
"Designing a Good Ventilation System"
"HRV or ERV?"