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Sustainusfarm
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# Posted: 19 Jun 2012 23:32
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I have a porch roof and I will be finally enclosing the underside of it with T-111 beadboard....question is: How do I ventilate it once it is closed in? Do I need to ventilate it to extend the life of the roof shingles? I understand I can put a continous vent along the soffit edge fo the roof, but what about the ridge area where it butts against the cabin wall? What is the best way to do this?
underside of porch roof
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another view
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toyota_mdt_tech
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# Posted: 20 Jun 2012 00:37
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You want inlet vents at the lower end, and outlet vents above. Can you install round holes with screens at the top between the rafters, (like bird blocking vents) I assume this goes into an attic??? Then the strip vent below like you mentioned.
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Sustainusfarm
Member
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# Posted: 20 Jun 2012 01:10
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It does not go into an attic...porch roof is attached to the sidewalls of the cabin...does this pic show it better??
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OwenChristensen
Member
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# Posted: 20 Jun 2012 10:22
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I doubt it will ever be a problem, but if you want you could put a vent in the shingles near the cabin. Porch roofs don't get quite as hot. It looked to me that you had a hip roof end to the porch roof, so I quess a gable roof vent is out.
Owen
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Sustainusfarm
Member
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# Posted: 20 Jun 2012 10:50
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I am thinking I will just run a continuous soffit vent along the bottom edge and leave it at that...any other ideas out there??
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Anonymous
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# Posted: 20 Jun 2012 18:44
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I really don't think it is necessary to vent a porch roof at all. Especially an open porch.
Ventilation is really only useful for two things: preventing ice dams when a roof is over a heated space; and keeping cooling costs down hot climates. Neither of those apply to a porch roof.
I say skip it.
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Sustainusfarm
Member
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# Posted: 20 Jun 2012 18:57
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I am enclosing the underside though...I was worried about heat build up and premature shingle failure?? I have seen unvented roofs here and shingles that have just curled right up...heres a pic...
asphalt shingles with edges curled up 2-3" on the corners
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Anonymous
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# Posted: 20 Jun 2012 19:30
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That can possibly be caused by an extremely overheated attic space in combination with moisture issues, but you only have a small gap between the porch ceiling and the roof deck. Not much air to heat up (and no moisture source).
Shingles that curled are likely really old, improperly installed, or defective (or all three!).
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johng
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# Posted: 20 Jun 2012 19:46
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If anything just put some soffit venting closer to the wall at intervals.
These combined with whatever you have on the outer edge will create a natural air convection that could even create a breeze on the porch.
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Sustainusfarm
Member
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# Posted: 20 Jun 2012 19:54
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Ok anonymous...I'll take that! And johng that sounds like a plan....Thanks all!!
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Sustainusfarm
Member
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# Posted: 22 Jun 2012 21:40
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Found an idea that could work....
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adakseabee
Member
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# Posted: 22 Jun 2012 23:30
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Sustainusfarm, after viewing the file you attached, the Corvar vent sure looks very similar to a ridge vent cut in half along its length. - Adakseabee
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Anonymous
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# Posted: 23 Jun 2012 19:12
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The cor-a-vent products work fine in most applications (although they can leak), and that one is what you could use for a shed roof coming off a wall. But again, that is designed for a roof with heated/cooled space below it.
You can use it if you want, but it's really not necessary for a porch roof.
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