Your stove -- whether it's gas or electric -- needs to have an operating hood and extraction fan over it. These hoods aren't just decorative -- they are essential to help control excess moisture in your home, as well as to help remove cooking odours.
These ventilation systems have a decorative exterior hood that hides the works and an exhaust fan and ductwork to extract the air, smoke and moisture. Obviously they need to be over the cooking area -- ideally they should extend over the stove's surface area. They need to be close enough to the stove to extract air, but not so close you can't comfortably cook. If they are too high, like many 'designer' hoods, they aren't doing an effective job.
It's ideal if your kitchen exhaust fan discharges to the outdoors. Never exhaust into the attic or soffits or crawl space. I've come across situations where the kitchen fans vent into the attic space; this is a really bad idea, for many reasons. First, the last thing you want to do is allow hot, moist air up into your attic space, especially in winter. It will lead to ice dams, mould, rot and a world of trouble caused by condensation. Second, if you ever had a fire on the stove, the exhaust fan could pull the fire into the attic, and allow it to quickly spread throughout the house.
The ducting should be smooth, with a short, straight run to the outside, with as few bends and angles as possible. This will help with your fan's efficiency in moving the air out. If the run is very long, you might need a bigger fan, so check with a pro. The joints need to be sealed, and if the duct runs through an unheated space, they should be insulated. If they aren't, condensation might form on the duct.
Kitchen exhaust fans come in different sizes and need to be appropriate for the size of your stove and house. It's very important that you get the correct size of ventilation fan. It's not as simple as 'bigger is better.'
Not only will your utility bills be higher because you are running an oversized fan, you are also exhausting larger amounts of heated or cooled (depending on the season) air from your home. And that's air you've paid to condition, which will affect the energy efficiency of your home. A fan that's too large will create air infiltration and compromise the building envelope.
If you have installed an exhaust fan that's too big, you can cause depressurization, which will lead to backdrafting. Backdrafting happens when exhaust fans pull the gases from combustion back into the house. These gases are the byproduct of fireplaces, hot water heaters, furnaces -- any combustion appliance that is vented to the outside -- and these gases are dangerous. They can kill you.
Most new homes are pretty airtight -- that's one of the reasons we have few problems with indoor air quality and mould growth. Airtight homes have mechanical ventilation systems such as heat recovery ventilators, to provide a fresh air supply. If you don't have replacement air coming in, you'll risk creating negative pressure (backdrafting), but also your fan will be starved for air and won't work properly.
You often see recirculating kitchen exhaust fans that don't expel air to the outside. They pull steam and smoke from the stovetop, filter it and recirculate it through vents at head level. These fans might remove odours, since they usually have a charcoal filter but they don't remove steam.
Don't forget that boiling water and steaming vegetables create a lot of moisture that needs to be discharged. These recirculating fans don't cause depressurization since they aren't vented externally.
They don't remove much odour or grease, and they blow into your face when you're at the stove. Replacing the filters can be expensive so people don't do it as often as they should, which means they don't work well.
I really believe you need to have your kitchen fan exhaust outside.
Catch Mike in his new series, Holmes Inspection airing Thursdays at 8 p.m. ET/PT on HGTV. For more information visit www.hgtv.ca
-- Canwest News Service
