How to properly vent lower roofs?

Discussion in 'Roofing and Siding' started by o2284200, Apr 24, 2013.

  1. Apr 24, 2013 #1

    o2284200

    o2284200

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    In the middle of 2nd day of re-roof...

    The 2 lower roofs, which share a small attic crawl space have what appears to be ample intake soffits on the front & sides but I'm trying to figure out the best way to vent outward from the near top without ruining aesthetics.

    I've added 2 goose-necks to the back of the upper roof but I really don't think that will look good in the front lower roofs. I'm considered trying to put some sort of "gable vent" on one or both ends but your thoughts & opinions would be greatly appreciated!

    FWIW, this is stucco over concrete block in Dade county, Florida within 1/2 mile of ocean.

    THANKS!

    [​IMG]
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    [​IMG]
     
    Last edited: Apr 24, 2013
  2. Apr 24, 2013 #2

    nealtw

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    The vents in the lower two photos are in the overhang on the sides, in most cases there isn't access to the attic from there unless someone cut into structure. In some cases the roof has been strapped sideways with 1x4 or 2x4 and then you will have some air movement there.
     
  3. Apr 24, 2013 #3

    o2284200

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    Thanks, there are intake soffit vents in both lower overhangs on the front too.
    And there's a crawl space that gives access to both lower overhang attics.
     
    Last edited: Apr 24, 2013
  4. Apr 24, 2013 #4

    nealtw

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    Stick your head up in the attic and see if there are openings from the attic to where the vents are on the sides, if not look to see if the roof sheeting is nailed to the rafters or is there strapping between the rafters and the sheeting, if the answer to both is no then you need more venting, if the answer is yes to one or both, you likely are fine.
     
  5. Apr 24, 2013 #5

    oldognewtrick

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    At the spot where the lower roof runs into the wall you should use a vent like Smart Vent that allows for head wall exhaust. Then the counter flashing should be fabricated go cover the Smart Vent.
     
  6. Apr 24, 2013 #6

    CallMeVilla

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    Heck! OldDog beat me to it ... Smart Vent has an application which applies to this situation. You might call it a "shed roof to wall" application because you have vents at the bottom but not at the top.

    Go to their site: http://www.dciproducts.com/html/smartvent.htm

    Get 'er done! Do it right! :D
     
  7. Apr 24, 2013 #7

    o2284200

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    Here's a shot in the attic looking at the lower right side of house or the 3rd pic from above. I can see the openings on this side but I was not able to get near the other side so I can only assume it;s the same set up.
    [​IMG]
     
    Last edited: Apr 24, 2013
  8. Apr 24, 2013 #8

    oldognewtrick

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    You should close off the side vents and have a continues vent strip along the eave for air intake and a continous vent at the wall for exhaust. The vents along the side will allow the vent system to short cycle.
     
  9. Apr 24, 2013 #9

    o2284200

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    Thanks, that looks awesome, would you go all the way across the top on each side of the lower roofs?

    Also was looking at O'Hagins...
    Has anyone had experience with their "Vents for Tile Roof Applications" http://www.ohagin.com/products_tile.asp ???
     
    Last edited: Apr 25, 2013
  10. Apr 25, 2013 #10

    CallMeVilla

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    The application requires a gap at the top. You can cut the sheathing to create this gap and apply the Smart Vent all the way across. The flashing will have to be determined based on your wall structure. The couter-flashing makes perfect sense.

    http://www.dciproducts.com/html/shedroof.htm#offwall

    shedroof2011.jpg
     
  11. Apr 25, 2013 #11

    nealtw

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    Depending on location and expected winds other thing have to be considered.
    http://www.floridadisaster.org/hrg/content/roofs/water.asp

    It dosn't look like we are worried about Ice dams, so the question becomes are the vents that are there not working. Was that part of the old roof in worse condition than the rest of the roof, then you may need more venting, but if not why bother. By the amount of dust on the wood work in the attic we can see the existing vent are moving air, as the dust is coming from outside.
     
    Last edited: Apr 25, 2013
  12. Apr 29, 2013 #12

    o2284200

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    At this point I'm looking at Solar Powered High Gable Fans on each end; one intake on the left roof & one exhuast on the the right roof but only because we do not want to put any type of hole on top of either lower roof. Anyone have experience with these gable fans and how do you think the rake vents would affect the fans & vise versa?
     
    Last edited: May 6, 2013
  13. Apr 29, 2013 #13

    o2284200

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    Thanks, location is Dade County Florida along the coast so we're expecting highest winds...and no ice damns to worry about, that's for sure!

    The area along the front eave edge on the right lower roof (inside attic pic) was in worse condition and needed several pieces of sheathing and all the facia wood replaced.
     
  14. Apr 29, 2013 #14

    nealtw

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    http://www.dciproducts.com/html/shedroof.htm
    The smart vent is aproved for Dade County, With that I would close theside vents and open more vents at the bottom or change the lower soffet to vented soffet and make sure you have air flow above the insulation at the bottom.
     
  15. Apr 30, 2013 #15

    oldognewtrick

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    What you want to avoid is short cycling the vents. Any vent inbetween the soffit and the top of the wall will compromise either intake or exhaust. More vent is not always better, it has to be proper venting. I suggest doing as Neal suggested.
     
  16. May 6, 2013 #16

    o2284200

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    Thanks! A lot of products are approved for Dade County but I'll have lean on my roofer/neighbor with 30 years experience down here; he's convinced that cutting holes in these lower roof tops is not a good idea. We've already hot mopped & back nailed the cap sheet as well as wrapped the roof to wall flashing in stucco so I'm pretty sure we're past the point of no return as far as venting roof tops.

    That's a good point about the air flow above the insulation. When I stuck my head in the attic, I also noticed the insulation was bunched up in some areas by the soffits where sheathing was replaced and looks like it's blocking air-flow. The crew left a bunch of water bottles and trash, too...How nice of them....But yes, this air flow obviously needs to be addressed, thanks!
     
  17. May 6, 2013 #17

    o2284200

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    Thanks! I'm wondering exactly how these rake vents are working with the soffit vents? Or are they working against one another?? How do I tell???

    Smart Vent aside, in what order would you rate the following as most "proper" venting?
    1) Leaving everything as is.
    2) Leaving everything as is but add one gable vent to each side above the highest rake vent.
    3) Closing off the rake vents and add one gable vent to each side above the old highest rake vent.
     
  18. May 6, 2013 #18

    nealtw

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    I guess the question has to be, what caused the damage that was found on the lower roof. Hate to argue with thirty years experience without hearing his argurment on not doing it. It sounds like most of the problem was over the exterior wall. You could improve the airflow there by installing an air shoot in every bay and changing the soffet to a vented product.
     
  19. May 6, 2013 #19

    oldognewtrick

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    Who is the shingle MFG and what type of shingle is it? I'll look up the mfg spec's for ventilation.
     
  20. May 8, 2013 #20

    o2284200

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    What cuased the damage that was found on the lower roof:
    IMHO...
    1) Water from upper roof with no gutter.
    2) Water from overhang essentially breaking & starting to fall off.
    3) Water seeping through old, neglected, broken & sometimes missing roof tile
    4) Water seeping through old 30/90lb hot mopped underlayment due to all of the above.

    His arguments:
    1) The fewer holes in the roof the better.
    2) Low profile venting options + hurricane wind driven rain = lots o' water in attic.
    3) Experience or lack of proven local history with a particular product.
    4) Aesthetics.
     

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