Helpful Tip: Beware the Oversized Kitchen Exhaust Fan
Filed under ask a geothermal expert
Beware the over sized kitchen exhaust fan
Homeowners often select oversized kitchen exhaust fans not realizing that they require makeup air – adding considerably to the cost of their house project.
A sales representative may not even mention the “make-up air” issue at all and the the homeowner can subsequently experience some serious sticker-shock at the cost of make-up air.
For example a 600cfm fan requires 10kW of heat to temper the air.
This amount of makeup air represents the capacity of an entire electric furnace in a small home.
Hi,
Can you expand on this, please? I assume that by “makeup air” you refer to the heated air that is required to replace the air that is vented out of the house along with cooking fumes when the fan is used…
The reason I ask: my wife looooves fans… She has a somewhat irrational fear of “moisture”, and runs the bathroom and kitchen fans for much longer than I feel is necessary, especially in wintertime, when the air being vented has just been expensively heated.
I’ve often wondered why fans are not factored in when doing energy efficiency audits.
You’re right, over ventilating homes is expensive, and ventilation code doesn’t address run time on fans. At best they ensure that the vented air is mechanically replaced so that air and moisture aren’t drawn into the home through the building envelope.
At the same time, controlling humidity in the house is important for reducing mould and mildew in basements, washrooms and kitchens, which impacts indoor air quality. HRV’s best for indoor air quality, and Panasonic makes a bath fan with a continuous low volume ventilation function (Whisper Green, 20-40cfm continuous). Changing out your main bathroom fan for one of these units will keep your wife happy and save you money.