Replies

1. 
   Guest_ | May 05, 1999 06:18am | #1

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   Jim
   i would ventilate just to prevent condensation as hot air accumulates in the attic space. I know this sounds extreme but in our Louisiana climate it is not abnormal for walls and ceilings to sweat in high humidity situations. I would use gable/turbin/ridge vents in combination with soffit vents. Either one alone is useless. The natural tendency is for the hot air to rise thru the gable(upper vents) and be replaced by cooler air entering thru the lower(soffit) vents. On my own house I have turbins combined with continuous soffit vents. The turbins turn even when there is no wind due to the natural flow of air thru the attic. Hope this helps

1. 
   Guest_ | May 05, 1999 07:48am | #2

   *Really? I -guess- hot humid air could condense as it cools at night (does Louisiana ever cool?). But I can't see how a significant amount of moisture would get in there, over an unconditioned space, and would seal it up tight.Don't intend to vent our open-air porch, but can be swayed...

1. 
   Guest_ | May 05, 1999 09:46am | #3

   *Why not just make it open beam? With the non-enclosed porch it will then be vented.

2. 
   Bill_Richardson | May 05, 1999 02:51pm | #4

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   Jim, I'd agree with Mike Mahan. I built a similiar add-on to my home in NC, another hot and humid state, it was screened in and on a concrete slab, we had no trouble. We didn't care for the openess of the ceiling with 2x6s showing, so some screen (to keep bugs out) and lattice work (to keep Mrs. Decorator happy) made it work. In three years in that home, we never had any condensation or heat exchange trouble. Good luck.

3. 
   Guest_ | May 05, 1999 05:15pm | #5

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   Jim,

   Without a cool surface for the moisture to condense out on, moisture shouldn't be a problem in this situation. The only rationale for venting here is to keep the roof deck a little cooler to extend your shingle life. I personally would build it closed and skip the venting. Millions have gone before you in this course of action.

   You'll have to rebuild the bottom half of the porch long before you ever have to worry about the roof decking.

   Steve

4. 
   john_roy | May 05, 1999 10:54pm | #6

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   I just built an open porch on my house and used a "flash filter" agaisnt the house to provide an exhaust outlet for the area between the porch ceiling and roof. I'd rather err on the side of caution rather than take a chance. A flash filter is an aluminum vent that goes agaisnt the house at the peak of the porch roof and provides ventilation in conjunction w/soffit vents.

5. 
   Jim_T. | May 05, 1999 10:54pm | #7

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   I'll be soon building my (open air) porch on my house soon (NE Ohio). It will be a simple 3/12 pitch roof tying into the house front, with ceiling joists with Pine 1x4 TG beaded boards for ceiling.
   This will not be an enclosed porch, however the roof and ceiling joists will create an enclosed structure.
   Question: Do I need to ventilate?
   Question: If so, what type?
   I've seen both gable end vents and soffit vents on open air porches in my area and have always wondered if they are necessary or effective.
   Thanks for your thoughts......