DIY Home Improvement, Remodeling & Repair Forum > DIY Home Improvement > Roofing and Siding > How to properly vent lower roofs?





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Old 04-24-2013, 06:52 PM  
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.



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Old 04-29-2013, 12:31 PM  
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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
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?


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Old 04-29-2013, 12:37 PM  
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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.
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.
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Old 04-29-2013, 12:50 PM  
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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.
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Old 04-29-2013, 06:37 PM  
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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.

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Old 05-06-2013, 09:30 AM  
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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.
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!
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Old 05-06-2013, 09:50 AM  
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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...
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.
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Old 05-06-2013, 09:53 AM  
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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.

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Old 05-06-2013, 01:26 PM  
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Quote:
Originally Posted by o2284200 View Post
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.
Who is the shingle MFG and what type of shingle is it? I'll look up the mfg spec's for ventilation.
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Old 05-07-2013, 05:09 PM  
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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...
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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