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  1. #1

    cold outside air penetrating ventilation

    I have a 1969 house in SE Minnesota. The slabs for the basement and one of the ground level rooms were poured over the in floor ventilation. In the ground floor room especially there is cold air coming out of the vents when the heater runs. It is a corner room and basically un-usable in the winter. The ventilation first splits at the furnace and one part goes straight into the ground and runs along the basement wall at the front of the house. It then wraps back at some point and goes up a half level to the ground floor room that I first mentioned.

    There is no crawl space to get at the ventilation so I don't think it can be repaired or insulated without digging under the house. What I would like to know is if it would be practical to just block up the ventilation running under the slab at the source and just install baseboard heat for those rooms? The basement is finished but it is also not that big and I was thinking for a more efficient fix to actually reroute the vent to go in the ceiling of the basement.

    Does anyone have any ideas that are maybe more creative than this? I have no experience in this field so I probably don't know about a lot of other solutions.

  2. #2
    Join Date
    Jun 2004
    4H: Hot, Humid Houston H.O.
    I am not a pro but a homeowner, in S.Texas no less... far from you. One true thing about all forced air systems is, the blower is operating against a back pressure and closing off that duct *will* increase the back pressure. They call it ESP, for "External Static Pressure". If your existing ESP is not excessively high then the blower will have little problem with that, however if you have a problem already with not enough duct for your airflow, then closing off the duct would aggravate a problem. No doubt if this problem existed, there would be a straightforward solution such as (an amateur speaking, remember) adding a duct run of equal airflow to somewhere that needs it.

    If there are other potential problems I sure would like to hear a pro say what they are.

    Best of luck -- Pstu

    P.S. In message #3 Beenthere pointed out a much more important problem. D'oh! That's why there is no substitute for a pro who knows what he is doing.

  3. #3
    Join Date
    Jan 2004
    Blocking off those supplies could create over heating issues for the furnace heat exchanger.

    Temp rise should be checked before hand.
    Contractor locator map


    How many times must one fix something before it is fixed?

  4. #4
    The section the goes into the floor have a shutter valve in the main duct coming out of the furnace. I can keep it 1/4 open to reduce the pressure. It seems though that the upper floors don't get enough airflow though and could use the boost by blocking the section that goes into te floor. I have shut it all the way in the summer since it is always low 70s in the basement even with 100 heat outside. I even have a fan to blow cold air up the staircase to help cool the upstairs. In the summer heat the A/C can't get the house below 80 degrees during the middle of the day. I talked to some HVAC reps at a Home Builders show during the weekend and should have someone coming out for a consultation next week.

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