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Community and Q&A

Recirculating OTR range hoods & washer/dryer ventilation

dburgoyne | Posted in Mechanicals on

I’m installing an electric range in a small house, and am considering a microwave with a built-in recirculating over the range hood (with filter). The house is very small (500 s.f.) and pretty tight, and California T-24 code requires continuous exhaust ventilation, which I plan to have in the bathroom (Panasonic WhisperGreen), but I’m afraid if I put an additional exhaust fan in, I’d have to provide ventilation in from outside. How effective are these OTR recirculating hoods?

I’m also putting a stacked washer/dryer in my pantry closet (natural gas dryer). Would this need supply air or ventilation? May keep some clothes in there as well, and not sure if the W/D would introduce moisture into this walk-in. I’m in Sacramento, zone 3, mostly cooling loads. Will be using 3/4 ton ductless mini-split for cooling and heating.

Thanks for any recommendations. I’ve never done a house this small before.

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  1. GBA Editor
    Martin Holladay | | #1

    First of all, I have no idea what an OTR fan is. I looked up "OTR" in an abbreviation dictionary, and got nowhere.

    First of all, you should talk to your local building department to verify local code requirements for kitchen ventilation. If you are required to install a range hood fan that exhausts to the outside, then you have to follow the code.

    If you decide to install a range hood fan that exhausts to the outside, most building codes do not require you to provide a makeup air system unless your fan is rated at 400 cfm or more. So one way to avoid the need for a makeup air system is to make sure than your fan has a low rating. For more information on this topic, see Makeup Air for Range Hoods.

    Q. "How effective are these OTR recirculating hoods?"

    A. Assuming I can ignore the letters "OTR," the answer to your question depends entirely on what type of cooking you do. If you like to roast meat, fry meat, grill meat, or do lots of deep-fat frying of any type of food, you probably want a range hood fan that exhausts to the outdoors. If you are a vegetarian who likes salads and often orders take-out, almost any type of recirculating fan will work.

    A large pantry closet with a washer and clothes dryer does not need makeup air. Assuming the dryer is vented to the outdoors, as required by building codes, these appliances will not introduce moisture into your house.

  2. bobhol | | #2

    O T R = Over The Range....appliance industry acronym ,regards Bob

  3. GBA Editor
    Martin Holladay | | #3

    "Home, home on T R"

  4. ChrisJS | | #4

    I made the mistake of using the microwave OTR recirculating exhaust system when renovating my home several years ago. I strongly advise against this approach if you cook at all. The small charcoal impregnated filters that fit into the microwave are totally useless at removing any cooking odors. Cooking smells linger overnight and into the next day after the evening meal. It is well worth the small added effort to vent the same built-in microwave exhaust through an exterior wall.

  5. dburgoyne | | #5

    I'm checking with the local building inspector, but I don't believe exterior ventilation is required for my electric stovetop, especially since I have operable windows in the kitchen. It's good I won't need any additional ventilation in my pantry/laundry room. My wife reminded me last night that our current, laundry room doesn't have any moisture problems.

    Any feedback on the effectiveness of recirculating (filtered) over the range hoods?

  6. dburgoyne | | #6

    Thanks for the reply, Chris. My range is 24" wide, and I've had difficulty finding a microwave that small with an integrated OTR vent that exhausts to the outside. Any recommendations? I suppose I could try to install a separate hood, and move the micro somewhere else, but space is so limited in this tiny kitchen.

  7. ChrisJS | | #7

    Not able to help with a 24 inch microwave exterior vent but you might consider a ceiling exhaust fan such as used in a bathroom. Before we renovated this was the set up in our Cape Cod cottage. Perhaps you can install a simple through the wall exhaust fan that works similar to the ceiling fan.

  8. dburgoyne | | #8

    I just heard back from our city plan checker who shared the attached document. Apparently, exhaust to the exterior is required for kitchens in order to meet ASHRAE 62.2. It says a minimum of 100 cfm is required for a range hood, but can also be met by a ceiling or wall mounted exhaust fan. It says that recirculating range hoods do not meet ASHRAE 62.2.

    Chris, I like your idea of a through the wall exhaust fan, right behind the stove, close to the source. I'm not sure how greasy exhaust may affect the ducting though. I'll also look into an actual hood as an option. I know they make some that are 24" wide.


  9. user-659915 | | #9

    The range hood may not be smaller than the width of the range but it can be wider. So you can use a standard 30" hood over a 24" range and it will actually be more effective in collecting odors and vapor. It will reduce your upper cabinet space by 3" each side of course.

  10. kevin_in_denver | | #10

    To Dan Burgoyne,

    You have misinterpreted what the information sheet says. It actually says that "recirculating range hoods.... cannot be used to satisfy the requirements of ASHRAE standard 62.2"

    Since you are meeting those requirements with the bath fan, you CAN use a recirculating range hood.

    Most of these OTR microwaves can be ducted either way, back inside or through the top into a duct. This duct is usually hidden by a cabinet. What I did in a recent build was to duct through the top of the cabinet, but not outside. I placed a bag of activated charcoal in that vertical duct. Since it has 10 times more charcoal than the the standard charcoal filter, I'm assuming it will work better and last longer: (I can't find the bag online any more)

    Activated charcoal is amazing stuff, lots of testing does show its effectiveness in odor and pollutant removal. In reality and practical use...., well my nose isn't good enough to tell.

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