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OTR Microwave as range hood in tight house?

DarkNova | Posted in Mechanicals on

I’m looking at a range hood for ventilation in a new, tight, house build. I’ve read the articles like:

which talk about buying a range hood with a small exhaust fan. Martin recommends 150 CFM to 250 CFM with a tight house.

On the other hand, whenever you read about over-the-range microwaves acting as vent hoods on the internet, they are always dismissed as inferior to “actual” range hoods. I’m talking about microwaves that are actually set up to exhaust to the exterior of the house through a duct, not the ones that are set up to just recirculate. Mostly the rational is that they don’t have high enough CFM ratings to be “good”, and people recommend 800+ CFM vent hoods instead, but that won’t fly with a tight house.

But many microwaves have CFM ratings of around 250 CFM, which fits the “tight house” recommendation.

So that got me thinking, if I’m not going to buy a big 800 CFM range hood because the house is too tight and I only want 250 CFM, why not get a microwave that vents to a duct? It would be cheaper and not take up counter space.

Is there some other reason I’m not thinking of that microwaves don’t vent well? Isn’t a CFM a CFM?

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  1. GBA Editor
    Martin Holladay | | #1

    Whether or not you will be satisfied with a 250 cfm exhaust fan depends entirely on your style of cooking.

    If you are a vegetarian, or the type of cook why gets a lot of take-out food, you don't need much of an exhaust fan.

    If you are a carnivore who likes a nice black coating on your steaks, and you use your range for three meals a day, you'll want a robust range hood fan.

    It's OK to install a big range hood fan if you really need one. But you'll have to install a makeup air system if that's the kind of fan you want (or need).

    To answer your question: As far as I know, a 250 cfm fan included in a microwave oven designed to be installed above a range will work as well as a 250 cfm fan without the microwave.

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