1. Welcome Hearth.com Guests and Visitors - Please enjoy our forums!
    Hearth.com GOLD Sponsors who help bring the site content to you:
    Hearthstone Soapstone and Cast-Iron stoves( Wood, Gas or Pellet Stoves and Inserts)
    Caluwe - Passion for Fire and Water ( Pellet and Wood Hydronic and Space Heating)

Roof vent pipe premature snow melting issue - how to fix?

Post in 'DIY and General non-hearth advice' started by Don2222, Apr 17, 2014.

  1. Don2222

    Don2222 Minister of Fire

    Joined:
    Feb 1, 2010
    Messages:
    7,079
    Loc:
    Salem NH
    Hello


    This is a very tenacious problem since I have tried many things. These houses was built in 1962 and the outside walls have approx 2" of fiberglass insulation. The stink pipe is for the toilet, tub, washer and sink.
    The pipe exits the roof above the right side of the bathroom window as shown in the pics below.
    Most of the houses in my neighborhood have this heat loss issue! ! !


    It seems that when the snow melts, why does the snow on the roof melt here? See pics
    The original stack was made of copper and only extended 6 inches off the roof. I tried extending it with pvc last year but that did not help very much
    See pics >> http://www.hearth.com/talk/threads/...on-the-roof-before-winter.89970/#post-1173890

    So this time I tore out the whole copper stack and replaced it with PVC so no heat would not be conducted up thru! Then I opened up the bathroom wall and tore out the 2" fiberglass and replaced with ROXUL ! Then I put in a new double pane double hung window and sealed all around it with foam sealant. The worst heat loss and air leak in the old windows was not the window but the frame around the window with no insulation between! ! !
    Before I closed up the wall I air sealed the gap where the ceiling sheet rock meets the top plate (2x4) in the exterior framing! Above the bathroom ceiling is 2x6 R19 Fiberglass insulation crisscrossed with R30. The roof rafters have rafter vents from the continuous strip vent in the middle of soffit all the way up to the ridge vent. with r3.8 reflectix foil stapled to the bottom side.

    See 2nd pic below. It is much better but why is it melting faster at this point now? Where is the heat loss? Sorry for the fuzzy pic

    Attached Files:

    Last edited: Apr 17, 2014

    Helpful Sponsor Ads!





  2. Highbeam

    Highbeam Minister of Fire

    Joined:
    Dec 28, 2006
    Messages:
    9,099
    Loc:
    base of Mt. Rainier on the wet side, WA
    I bet your pipe is blocking the ventilation air that would normally enter in the soffit, travel up the underside of the roofing unimpeded, and then out the top. That big plumbing vent is slowing the flow of air relative to the others and slow air isn't able to wisk away your leaked heat from the house so it melts the snow there.

    That tiny dusting of snow could melt if a mouse farted under it.

    It's an idea.
    Warm_in_NH and heat seeker like this.
  3. heat seeker

    heat seeker Minister of Fire

    Joined:
    Feb 25, 2011
    Messages:
    1,977
    Loc:
    Northern CT
    Maybe heat gain - from the sun, reflecting off the pipe? Yeah, a long shot…I like Highbeam's idea.
  4. Highbeam

    Highbeam Minister of Fire

    Joined:
    Dec 28, 2006
    Messages:
    9,099
    Loc:
    base of Mt. Rainier on the wet side, WA
    In the fuuzzy picture, you can almost see a reduction in meltoff at the ridge in that same rafter bay which would jive with a lack of flow.
  5. Utilitrack

    Utilitrack Feeling the Heat

    Joined:
    Oct 14, 2008
    Messages:
    288
    Loc:
    Central ME
    No such thing as a "premature snow melting issue" after this winter!;)
  6. Don2222

    Don2222 Minister of Fire

    Joined:
    Feb 1, 2010
    Messages:
    7,079
    Loc:
    Salem NH
    Good ideas

    I just found a pic of the issue before the new window, before the Roxul insulation in the outer wall and before I put the PVC in and air sealed it.

    It looks like the problem has moved to the right!

    The only thing that would make sense, is the fact that I air sealed where the ceiling sheet rock meets the top plate above and slightly to the right and levt of the window. I did not air seal the section to the right where the problem shifted!

    See pic. Click to Enlarge.

    Attached Files:

    Last edited: Apr 17, 2014
  7. Highbeam

    Highbeam Minister of Fire

    Joined:
    Dec 28, 2006
    Messages:
    9,099
    Loc:
    base of Mt. Rainier on the wet side, WA
    I don't see how it moved much if at all. Your rafter spacing is 16 or 24, probably 24".
  8. woodgeek

    woodgeek Minister of Fire

    Joined:
    Jan 27, 2008
    Messages:
    2,711
    Loc:
    SE PA
    I'd vote for an airsealing issue near the top plate. Is there something in the wall cavity under that could be feeding the leak. That is, the gap in the plate might be uniform along the wall, but there might be something in that wall cavity allowing air in??
  9. Warm_in_NH

    Warm_in_NH Minister of Fire

    Joined:
    Dec 17, 2013
    Messages:
    588
    Loc:
    central NH
    I think Highbeam hit the nail on the head with the obstructed air flow. It's not uncommon. If you're not getting leaking ice dams I wouldn't worry too much about it.
  10. Don2222

    Don2222 Minister of Fire

    Joined:
    Feb 1, 2010
    Messages:
    7,079
    Loc:
    Salem NH
    Yes, Woodgeek, I think you are right on track here. The proof of this happened when I took the wall board off on the outside wall in the bathroom. The warm air in the bathroom super fed the air leak between the ceiling sheetrock and top plate and made the melt mark 10 times greater!

    Now in this last case, I think that because there is only approx of 2 inches of insulation in the 2x4 outer wall, that there is warm air in the cavity on the inside of the insulation. This slightly warm air is being drawn up by the vacuum created when the soffit air runs up to the ridge vent. Why it only occurs near the bathroom is another question, but because of the hot showers, the bathroom is much warmer and humid too!

    I was amazed when I saw that gap between the ceiling sheet rock and the top plate! ! !
    This would also explain why the melt area is close to the edge of the roof where that gap is! ! !
    When I get up there and seal it I will take pics. Did you seal that area in your house Woodgeek?
    Last edited: Apr 18, 2014
  11. Highbeam

    Highbeam Minister of Fire

    Joined:
    Dec 28, 2006
    Messages:
    9,099
    Loc:
    base of Mt. Rainier on the wet side, WA
    I'm interested in the pics Dan because I too have a 1963 built house with that weird 1.5" thick R-5 batt insulation in the 2x4 walls.
  12. Don2222

    Don2222 Minister of Fire

    Joined:
    Feb 1, 2010
    Messages:
    7,079
    Loc:
    Salem NH
    Hello HighBeam

    Here is a pic where we shot the Expanding Foam from below when the sheet rock was off! The gap got larger, because the sheetrock was not straight against the top plate!

    Anyway, it should be easier and better to just put the foam in from the attic. I put plywood sheets across the rafters so I do not fall in, then just scrunch down there close to the gap and do the foam thing. :)

    Attached Files:

    Last edited: Apr 18, 2014
  13. woodgeek

    woodgeek Minister of Fire

    Joined:
    Jan 27, 2008
    Messages:
    2,711
    Loc:
    SE PA
    I got all the interior and gable end top plates with Silicone caulk for 'attics'. With my low-slope roof I couldn't reach the exterior walls on the eaves. I had pros hit that area with sprayfoam. Not clear how effective that 'spray and pray' method is, but even with a huge snow load (for us) last winter, I did not get many icicles, and no ice dam problems.
    Last edited: Apr 19, 2014
  14. Don2222

    Don2222 Minister of Fire

    Joined:
    Feb 1, 2010
    Messages:
    7,079
    Loc:
    Salem NH
    Very good, That spray foam probably got it. I have a 30 Deg slope so I can get in there. I will get that area soon.
    Last edited: Apr 18, 2014
  15. BrotherBart

    BrotherBart Hearth.com LLC Mid-Atlantic Division Staff Member

    Joined:
    Nov 18, 2005
    Messages:
    28,626
    Loc:
    Northern Virginia
    It would be harder if the slope was Celsius.
  16. Don2222

    Don2222 Minister of Fire

    Joined:
    Feb 1, 2010
    Messages:
    7,079
    Loc:
    Salem NH
    Yes, I was thinking to much about heat lately! ! ! LOL

Share This Page