Enclosing/insulating a porch

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Old 11-12-10, 04:58 AM
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Enclosing/insulating a porch

Finished framing porch enclosure (Georgia). I inlet corner braces and am using OCB on corners as well for structural integrity. I'm planning to use sheet foam (with the silver lining) to sheath the rest of the porch (same thickness as OCB).

From there we plan to housewrap and then cover with lap siding. We're doing the housewrap right, using compatible tape and installing drip mouldings over windows and doors.

Question: Is there any problem with using OCB and sheet foam side by side? The wood has a much lower R value of course, but any other problems?
 
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Old 11-12-10, 08:07 AM
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What's OCB?

or did you mean OSB?
 
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Old 11-12-10, 03:13 PM
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OCB's are rolling papers for Prince Albert. Jon, you will find OSB and the insulation boards not to be too dissimilar in cost. I would opt for OSB all around 1) for structural stability 2) for a place to nail your siding in odd end places not on studs.
The insulation board won't afford that much insulation properties. That will come on the interior wall cavity insulation.
Your plan is good, just do the OSB thingy. You can come up from Covington to the mountains and thank me later.
Have you decided on the wall thickness, yet? 2x4, 2x6? Windows? Sliders IMO are best for porches. I do a lot of remodels up here and most of my customers request sliders as opposed to double or single hung.
 
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Old 11-12-10, 07:40 PM
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Good you used OSB on the corners rather than rely on the let-ins (inferior).
1. The minimal R-5 you get must be for the foil facing as a vapor barrier?
2. Where in the State are you?
3. What type? of lap siding may be critical with foam.......

Gary
 
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Old 11-13-10, 06:08 AM
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Gary, he's just east of Atlanta..............
 
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Old 11-13-10, 10:05 AM
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I looked him up as being -200 miles South of Atlanta, if that's correct? Then he would be in a "Hot/humid" zone- no vapor barrier/retarder on the inside: BSD-106: Understanding Vapor Barriers — Building Science Information

Still waiting on the siding as wood/house wrap needs back-priming or rain-screen, or drainable house wrap-not flat. Typar would not be better than Tyvek or 30# paper to ease the moisture passage with lower perm ratings due to moisture going both ways all year.

Gary
 
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