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  1. #1

    A floor vent question

    Hi , i have a question regarding reducing excessive air flow through a floor vent in a trailer home, the vent is not part of a duct system it is cut directly into the floor. I am trying to find a way of reducing heat loss through excessive movement of air through the vent, there are other vents in the wall which provide clean air to the interior.


    The vent in the floor is designed to remove waste gas (LPG) it is not required to provide clean air to the building interior.
    The vent is cut into a timber floor and consists of a grill, the grill just vents to the outside.

    The floor is suspended about 60cms from the ground and is open to external elements, primarily wind passing beneath the structure.

    Because the vent is floor mounted and is designed as a safety measure to remove LPG gas waste etc the vent cannot be blocked or covered to reduce air flow.

    My understanding is that as the wind speed beneath the floor increases then so does the amount of air it draws through the vent ( i presume this is because of the difference between internal and external air pressure)

    Is it possible to fit something beneath the floor (and the vent) to reduce the effects the high wind speed would have on drawing air from the internal space, without reducing the removal of waste gas from the LPG heating system?



    I am trying to find a way of reducing the amount of air being drawn through the vent in high wind conditions to the floor space below, while still maintaining safe ventilation of waste gases.

    Thank you in advance for your informed replies.

  2. #2
    Join Date
    Jul 2004
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    Charleston, SC
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    The vent in the floor at the furnace is to bring in air for the combustion process while the furnace is in operation. As already stated it can not be blocked. Can the furnace cabinet be sealed to enclose this vent with the furnace but separate it from the rest of the house? You may have to install or extend a return duct out of the space once sealed.

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  3. #3
    Join Date
    Sep 2009
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    Just install some kind of blocking to keep the wind from blowing across the opening that will not block the opening, but will stop that "venturi" effect you mentioned.
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  4. #4
    Thanks for the replies,

    Cartercrew, the trailer home is a British made one, it also has vents in the walls as well as the floor, i was under the impression that the floor vent was solely concerned with removing un burnt LPG gas, is this not in fact correct?


    Tipsrfine, so if i were to place something beneath the actual floor this would reduce the air pressure difference and so slow down air leackage when the weather is windy? Would a vented pipe that reached to the ground provide a safe method of achieving this, or would it act like a chimney and draw air down the pipe?.

  5. #5
    Join Date
    Sep 2009
    Location
    Arnold mo
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    Quote Originally Posted by numbnah View Post
    Thanks for the replies,

    Cartercrew, the trailer home is a British made one, it also has vents in the walls as well as the floor, i was under the impression that the floor vent was solely concerned with removing un burnt LPG gas, is this not in fact correct?


    Tipsrfine, so if i were to place something beneath the actual floor this would reduce the air pressure difference and so slow down air leackage when the weather is windy? Would a vented pipe that reached to the ground provide a safe method of achieving this, or would it act like a chimney and draw air down the pipe?.
    I was just referring to the fact that you said wind was blowing across the outside outlet, which would create a venturi effect. I would recommend someone in your area that is BPI certified and has experience in mobile homes. "Air out = Air in". You may have issues that someone experienced in mobile homes could assist you with. I surely would not make any changes without consulting an expert as such changes could create a dangerous/deadly condition.
    An answer without a question is meaningless.
    Information without understanding is useless.
    You can lead a horse to water............
    http://www.mohomeenergyaudits.com

  6. #6
    Join Date
    Jun 2011
    Location
    Houston area
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    1,493
    Are you in England? Is there skirting around the trailer's perimeter? Without a picture it's hard to say but I'm thinking a small plenum underneath the trailer with internal baffles and a 1/4" x 1/4" mesh inlet screen to keep out the Chesire cats might work.

    And I really don't think the vent is an exit for un-burnt LP. It does sound more like a combustion air supply.
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  7. #7
    Quote Originally Posted by tipsrfine View Post
    I was just referring to the fact that you said wind was blowing across the outside outlet, which would create a venturi effect. I would recommend someone in your area that is BPI certified and has experience in mobile homes. "Air out = Air in". You may have issues that someone experienced in mobile homes could assist you with. I surely would not make any changes without consulting an expert as such changes could create a dangerous/deadly condition.
    Thank you, i certainly wouldnt modify any ventilation. I am just trying to get my head around a possible solution, i dont want to stop it from removing air, it just seems to remove a greater volume of air when the wind blows.

    In theory, your opinion is to follow a course of action which would reduce the venturi effect?

  8. #8
    Quote Originally Posted by Cooked View Post
    Are you in England? Is there skirting around the trailer's perimeter? Without a picture it's hard to say but I'm thinking a small plenum underneath the trailer with internal baffles and a 1/4" x 1/4" mesh inlet screen to keep out the Chesire cats might work.

    And I really don't think the vent is an exit for un-burnt LP. It does sound more like a combustion air supply.
    Yes i am in the uk, there is no skirting around the underside of the van, could i create the same effect with a "mini" skirt around the actual vent?

  9. #9
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    Sep 2008
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  10. #10
    Quote Originally Posted by jpsmith1cm View Post
    Skirting will reduce your energy consumption.
    I understand that skirting will reduce energy consumption, however my site owner wont allow skirting to be fitted. So if i can install extra insulation beneath the floor to reduce moisture ingress and air tighten the floor space, my only problem i have left is to reduce the heat loss through the floor vents.

    These floor vents are where large volumes of warm air are being lost.

    In my mind i have an image of a mini skirting system around the vent openings to reduce air flow and prevent unnecessary heat loss, is this feasible?

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