# Converting 3 season porch to 4 season....how should I do the floor?



## Ron6519 (Mar 28, 2007)

How were you planning on controlling moisture from the ground?


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## mph7794 (Jun 5, 2011)

So, after speaking with the inspector, I will have to get an r-30 insulation in the 7.25" space. He recommended spray foam but admitted it is high in price. He said we could use 6" of rigid foam to get the r-30 as well. We also need r-44 in the ceiling (also 2 x 8), so I got my first quote for spray foam and it was $1790. That is twice as much as my doors and windows! 

Anyways, if I were to do the rigid foam, can the 6 inches of foam be suspended by wire zig zagging the joists (1.25" from the bottom of the joist) rather than using any plywood? does a vapor barrier need to be between the ground and the foam or between the foam and sub-floor. Or, is the foam itself which claims to be "impervious to moisture" provide the barrier? Thanks for the help!


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## Ron6519 (Mar 28, 2007)

I'd put a 6 mil plastic over the dirt to keep the moisture at bay. I'd keep it tight to the rooms perimeter so moisture doesn't escape at the edges.
I'd also install 2 foundation vents for cross ventilation.


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