floor insulation for new enclosed porch


Old 12-07-07, 08:19 PM
Thread Starter
Join Date: Jan 2005
Posts: 13
floor insulation for new enclosed porch

i built a wrap-around porch on the house last year, and have now enclosed a 10ft x 20ft section (with southern exposure and a couple of skylights) into a sunroom. the porch floor is all 5/4 x 6in cedar (tight spaced with some gaps - not T&G). i'm looking for input on my current plan for the floor. entry from the house and rest of the porch into the sunroom is via a pair of sliding glass doors whose thresholds is 6in above the porch decking. i'm thinking of first laying down a thick poly sheet as a air/vapor barrier, followed by a double layer of 2in DOW blueboard styrofoam insulation panels (alternating the lay). then i would glue down a layer of luan and add a pergo (or like wood floor). anyone see potential flaws in this concept?
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Old 12-08-07, 04:52 AM
airman.1994's Avatar
Join Date: Dec 2005
Location: VA
Posts: 5,632
Onlt thing I see is you will have 5 VB.
Old 12-08-07, 06:27 PM
Join Date: Nov 2001
Location: Taylors, SC
Posts: 9,483
Unless you put plastic under the porch, there will be moisture entrapment between the soil and the plastic on the flooring possibly causing problems with the cedar.

It seems that all that Dow foam would make for a mushy floor. That might affect the performance of the Pergo.
Old 12-09-07, 09:34 AM
logcabincook's Avatar
Join Date: Oct 2006
Location: Rocky Mountain Foothills
Posts: 549
In planning to enclose our front porch (standard decking right now), the following was recommended:

Put a vapor barrier under the porch joists
Install exterior grade plywood under the joists and vapor barrier.
Fill the joist cavities with standard insulation
Top off the joists with plywood/cement board (depending on whether we do laminate or time flooring)

I do not know if this is "legal" or not but it sounded good to me!

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