Is your kitchen the world’s smallest fast food restaurant?

Don’t revoke my Asheville residency for admitting that I love fast food french fries.  Sometimes fast food makes sense.  You’re busy, you need food NOW, and right next to the highway there’s this little kitchen pumping out food with salt and ketchup and everything that’s right (and wrong) about America on it.  I get it – flame broiled is imprinted on our national DNA.  But can we stop turning our homes into fast food restaurants?

If you’re sure this post can’t be about you because you love cooking and live in Asheville and have a CSA membership…. don’t stop reading just yet.  This post is probably about you.  There’s a problem that happens in fast food restaurants that I’m seeing more and more often in homes.  And it’s the gourmets among us who are most at risk.

Here’s how it happens in restaurants.  There’s a giant cooktop with multiple burners that probably all get turned on at the start of a shift and stay on until closing.  This generates huge amounts of heat and cooking byproducts that probably aren’t all that great for workers to breathe.  They deal with this by putting a big, high flow rate kitchen hood over it to pull that air out of the restaurant.  To balance the pressure, makeup air has to come in somewhere.  Usually code requires a lot of ventilation air for the dining room, so the designer might bring air in for the dining room and let it go out the range hood.  It’s also possible to bring in make-up air somewhere near the range hood.  Sometimes the balance of incoming and outgoing air gets messed up.  Usually the kitchen hood pulls out more air than is coming in and the pressure inside goes negative.  You might notice that the door gets harder to pull open.  Or the air in the restaurant might get more humid on rainy days.

Here’s how it happens in your house.  You love to cook and you have to cook on gas.  You fall in love with a big, shiny commercial cooktop.  The kitchen designer tells you that it requires a 1,000 cfm range hood.  This all sounds great – bigger, better, shiny, good.  Right?  Wrong.  Your house doesn’t have any makeup air, and this range hood isn’t going to come with its own.  No one is going to mention it unless you’re building a new house and your green building certification has a problem with it.  So you install it, fire it up and maybe (hopefully, even) you don’t notice anything.

Here’s what’s happening when you use the giant kitchen range hood.  You create a giant negative pressure in your house.  If you have a low-efficiency (atmospherically vented) gas appliance, there is a risk that it will backdraft, and the resulting carbon monoxide poisoning could kill you (unless you have CO detectors, which everyone should have).  If your house is really airtight, it’s theoretically possible (but less likely) that even a power vented or closed combustion model might pose a risk.  Don’t even think about lighting a fire in your fireplace.  In fact, you might just suck the ashes out of your firebox and onto the floor.  Your front door may make a whistling noise.  A rush of cold or hot or humid outside air comes into your house through whatever cracks and crevices it can find, and your heating and air system is NOT sized to deal with it.  Even if it can keep up, You’re using a LOT of energy.

How widespread is the problem?  If a 300 cfm kitchen fan actually moved that much air, I estimate that about half the new homes we certify would be depressurized more than I’d like.  And at 1,000 cfm almost all new homes would be.  It works out conveniently that most fans don’t actually move as much air as they’re rated to, so usually it works out that a 400 cfm fan will test OK.  If the house is really tight, you may want to go smaller.  In my personal house I have a 200 cfm micro-hood.

A right-sized kitchen hood

So what are the alternatives?  This is one of those arguments I never win, but let’s lay out some ideas anyway.  First, you could fall in love with an induction stove.  Before you say no, you should at least try one – mine boils water in 30 seconds and turns down instantly.  And since the cooktop stays cool, it’s a breeze to clean.  If you are actually one of the rare individuals who is going to  roast something directly in the gas flame you could also fall in love with a really nice outdoor gas grill, or invest in one of those little handheld kitchen torches.  Or if you’re going to buy this stove and hood no mater what I say, you can design makeup air to come in somewhere near the hood automatically whenever it turns on.  This adds to cost, uses a fair amount of energy, and will probably make your house less airtight even when the hood isn’t on.  Which is why I’d rather you put non-commercial equipment in your residential kitchen.

Copyright 2012 Amy Musser