# Need Material to cover batt insulation



## BillGulledge (Nov 4, 2012)

Replacing the insulation on the underside of the floor of my coast house. House is on pilings, with 12' clear underneath. When you stand underneath and look up, you see the floor joists -- e.g. no plywood ceiling. Floor joists are 2 x 6 0n 16" center. I plan to use batt insulation with paper backing. Once the insulation is installed, I need to "cover" it (from underneath) to protect the insulation from wind and to form a vapor barrier. I am thinking about sheet material that I can staple in place -- something like Tyvek House Wrap (but the Tyvek prople tell me this is not a good application for their product.) Eventually, I'll put in 1/2" treated plywood but for now I am looking for a cheaper alternative. I have about 1800 sq ft to cover. I got a roll of salvage vinyl roll roofing material several years ago - manufacturing defect so they were giving it away - that would seem to be perfect for my application. Any ideas anyone?
Thanks for any input.


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## tinman (Apr 13, 2005)

Use the black plastic that they put underneath travel trailers

Tinman


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## trout250 (Aug 24, 2005)

black plastic or use a heavy grade neoprene and use wood lathe strips to hold it up.


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## Slip (Jul 25, 2006)

Would insulation foam such as foam board work better?


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## mas360 (Nov 21, 2006)

tinman said:


> Use the black plastic that they put underneath travel trailers
> 
> Tinman


And then you have to redo it every five years. That stuff does not hold up well at all.


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## redman71 (Jan 11, 2005)

*underside*

If it were me, I would go with the Tyvek or Dow housewrap anyway. As long as it is not in direct sunlight it will last a long, long time. Staple the snot out of it with a hammer tacker and your should have plenty of time to put the plywood up.

What kind of flooring do you have above? You want to be careful not to create a moisture trap. If you have an impermiable flooring (like sheet vinyl) and you put a moisture barrier underneath (plastic)
, you have created a moisture trap that can lead to mold and rot in the floor joists over time.

When I was building homes a couple of years ago, we used the Dow because it had some permiability to it.

http://msdssearch.dow.com/Published...foam/pdfs/noreg/179-07301.pdf&fromPage=GetDoc


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## padrefigure (Aug 22, 2006)

Also put the paper side up against the subfloor. Use the wire supports to keep the batt insulation tight against the subfloor. You do not want a gap between the subfloor and insulation. If you could get someone to spray foam insulation, it would be even better, but more expensive.


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