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Reversing Negative Pressure

AA2 | Posted in Energy Efficiency and Durability on

Hello, I live in a 1911 Bungalow that has some great first floor insulation (hard packed cellulose in the back of the house) with spotty blown in insulation on the first floor and ok fiberglass insulation in the ceiling and floor of the second floor (2nd floor is dormered and mainly roof) with a stairway in the middle of the house. In the winter, there is airflow movement from the first floor to the second (yes, upward). When burning a fire in the fireplace, this upward movement of heat is welcome, at other times, the upward movement of cold air is a detriment. Question: how can I control and manage the movement of heat between floors in this case?

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  1. Jon_R | | #1

    Air sealing the entire house will reduce stack effect driven flow. And it reduces energy use. Use a blower door or fan to find the leaks.

  2. Expert Member


    Air-seal, air-seal, air-seal.

  3. walta100 | | #3

    The way I see it old houses leak a lot and half story building leak 4X as much.

    If you going to be paying a contractor, to do the air sealing look for one that owns a blower door and will test before and again after.

    If this is a DIY air sealing job consider taping a box fan into a window and using incent smoke to locate the leaks.


  4. Expert Member
    BILL WICHERS | | #4

    One more vote for air sealing, since you’re probably feeling stack effect in action.

    Easy low-hanging fruit items that are common leakers are:

    Attic hatches. These are BIG leakers! Insulate them with rigid foam, seal them with weather stripping and draw latches to pull them tight against the weather stripping for a good seal.

    Recessed can lights. Usually these are sealed by boxing over the top with rigid foam on the attic side.

    Bathroom exhaust fans. Make sure they have dampers, and make sure they vent to outdoors and not into your attic.

    If you go into the attic, take a few cans or canned foam with you and seal all the obvious penetrations in the top plates for pipes and wires. This along with the things I mentioned above should help a lot.


  5. AA2 | | #5

    Thanks All -- one additional challenge in this case is that the second floor is finished and would require taking down walls to add more insulation. Knee walls are all around the perimeter meaning either strategic holes in the right places to be patched up later or other alternatives. Unfortunately, the second floor is what used to be the attic and it is all living space now. That said, the second floor holds heat in the summer - just not in the winter. In essence, I am looking for as many tweaks as can be made short of taking off all shakes to wrap or removing all knee walls to re-insulate.

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