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Snow and Ice Buildup

Post in 'DIY and General non-hearth advice' started by mayhem, Jan 13, 2011.

  1. mayhem

    mayhem Minister of Fire

    Joined:
    May 8, 2007
    Messages:
    1,938
    Loc:
    Peru, MA
    Had to go out for an errand and while out I took a good look at houses and their roofs. There are almost no exceptions. Houses with roofs facing either south or west have icicles all along the edge of that roof face. Look on the opposite side of the street and I see houses with zero icicles on the north or east sides.

    So either we have a significantly different weather here up north, we have an extraordinary number of houses with poorly insulated roofs or we have alot of solar melting.

    I don't recall witnessing much dripping off the icicles during the night, only during the day.

    Then why is the warmest surface temperature on my ceiling out of line of sight of the stove? Why do I not have icicles forming over that section?

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  2. Lighting Up

    Lighting Up Feeling the Heat

    Joined:
    Jan 30, 2010
    Messages:
    340
    Loc:
    Roc City NY
    Icicles only form for two reasons:

    1. Cyclic heating/cooling due to fast changes in the ambient air temp combined with solar heat gain, or

    2. Because heat is escaping from inside the structure and getting under/onto the roof decking, melting the snow on the roof, creating water which drips downhill and refreezes when it gets away from the heat.

    The first process happens rarely in most areas, usually at the transition into or out of winter, which we are not in. The second process happens all winter, in structures which are not properly insulated or air-sealed, or in structures in which the internal heat overwhelms the insulation of the structure. The second process can be aggravated by the first.

    You see icicles commonly in the winter, but as I've said before, you don't commonly see them in well-insulated, air-sealed houses, unless the first process is at work. For example, my house never has icicles anywhere, even on the south-facing roof, except for a few days in Feb/March, as we approach the thaw. Then they're gone. That's it.

    My neighbor's house, however, has icicles nearly all winter, on all sides.







    +1
    let me add, it sounds like you have a lot of steady cold air coming in that house sending the hot air up. You have the problem w/or w/ out the stove but when your furnace only was heating you say it was very cold and it ran never shutting off.

    I think you need to stop that cold air coming in first and put all ceiling fans on reverse with some other fan on your landing facing at your stove or down. I also think it would be worth having a energy audit with a thermal camera.

    Also if I'm reading this right, the hot air could be escaping at the chimney pipe roof exit and that's why your ice is larger in line with the chimney pipe over the door, if I understand your pictures.

    Great looking house keeping thinking you'll figure it out.
    md
  3. colebrookman

    colebrookman Minister of Fire

    Joined:
    Feb 7, 2008
    Messages:
    776
    Loc:
    Middlefield, Ma
    Next time there is little snow on the roof ask the local fire chief to bring the thermal camera up and scan the outside of your house. Do it at night and make sure your wood stove is burning. You should be able to see where the heat is escaping and which areas to concentrate on. A small donation to the donut fund goes a long ways. He may even like the idea and use it as a fund raiser for the dept. Be safe.
    Ed

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