Downdraft cooktop-alternatives to outside venting??

Discussion in 'HVAC Heating & Cooling' started by Eagle45, Jan 24, 2009.

  1. Eagle45

    Eagle45 New Member

    Messages:
    6
    Is there a way to vent a downdraft cooktop without having to punch a hole out the wall. I'm not thrilled with having to do this due to the heat loss and/or cold drafts from the vent. Furthermore, I have ICF cement walls, so it's a bit of a job.
    What about tying it into the ducting of my fresh air heat exchanger?
    What lead me to this thought was some very sparse information elsewhere where they said you could wire the cooktop fan switch to turn on your furnace blower, but haven't been able to find any further detail on what they were getting at.
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,892
    Location:
    New England
    Vent it outside! You certainly don't want the smoke, grease, and other cooking smells wafting throughout the whole house. You'd lose the whole benefit of having a vent in the first place and be generating a huge maintenance issue as you'd potentially have a fire pit from grease and embedded dust that would accumulate in the ductwork. Very bad idea...vent it outside.
  3. Eagle45

    Eagle45 New Member

    Messages:
    6
    But if I tie it to the outbound duct of the fresh air heat exchanger and the furnace fan is running it will be going outside, not wafting through the whole house. It's just room teperature air coming out this duct, not combustion gases, so I don't think there is a risk of fire from grease buildup (no different than the grease buildup in a dedicated duct).
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,892
    Location:
    New England
    You'll gunk up the heat exchanger and put a coat of grease on the inside of your duct...not good. Bite the bullet and do it right.
  5. Eagle45

    Eagle45 New Member

    Messages:
    6
    How would it gunk up the heat exchanger when the furnace fan is running and generating positive pressure from that point? Cooking fumes would not be passing through the HE. If the cooktop vent is tied in 2 feet from the ouside vent, grease buildup will only be a problem in that 2 foot section (if it does buildup at all-how many hood vents go for years & years with no attention?). Would love to hear from some energy concious creative thinkers.
  6. shluffer

    shluffer New Member

    Messages:
    81
    Location:
    Connecticut
    just to clarify the situation, the duct you want to tie the cook top into is pushing air out of the house from the point you are tying it in? wouldn't you be concerned that the air you are trying to push out of your house from the heat exchanger would end up in your kitchen?
  7. Eagle45

    Eagle45 New Member

    Messages:
    6
    Thanks for your thoughtful response. Yes,that is one piece I was looking for advice on. Maybe a one-way damper coming off the cooktop duct?
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,892
    Location:
    New England
    And will this air go by the air-to-air heat exchanger in the ventilation system? There's a lot of grease in that exhaust even with the filters...best to keep the path short as possible and dump it outside.
    Last edited: Jan 25, 2009
  9. frenchie

    frenchie Jack of all trades

    A heat exchanger will catch a lot more of the grease than an open pipe. Not only due to way more surface area, but also that as the exhaust air is being cooled, more grease will condense on those surfaces.

    Re-reading the thread, are you talking about tying in after the heat exchanger? Maybe not so crazy, then.

    The switches to activate your furnace blower when you turn on your cooktop exhaust fan, are not for tying in the two together. They're for providing makeup air, to prevent depressurization.
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