Hello all. My father and I are in the process of building a house here in New Orleans. We have recently moved here from Indiana where the foundations are very different. Our system is a raised home built on top of a chainwall. The bottom of our floor joist will be sitting 2’6″ above grade. Our plans call for an R-30 rating under the floor. We are in the process of discussing our options for insulation applications and have decided to go with typical fiberglass batts. However, we do not know how we should keep it up there. Is it normal to skin the underside with plywood or some other kind of sheathing?
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Make sure whatever it is will keep the rats out.
We've used OSB for that. a pain to do and you want to use screws so you can take it down to add wires or fix stuff. R-19 should be enough for NOLO I would think.
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"You cannot work hard enough to make up for a sloppy estimate."
i'm not a pro, but i've piddled on old houses in baton rouge and north louisiana for about 40 years, and I have never seen an old house on piers where the floor was insulated. lumber yards used to sell stiff wire with sharp ends, that were slightly longer than the joist spacing. slide the batt between the joist and jam the wire in to support.i wouldn't think the payback period would justify the expense of insulating the floor.also, how well is the chain wall vented? down here, chain walls are usually on the front for looks, but the remainder of the house is pier and beam. in new orleans, the groundwater is about 3 inches below grade, so ventilation is hugely important. without a good vapor barrier, i would be concerned that floor insulation would hold moisture against the floor.
Edited 11/18/2008 8:13 am ET by davem
Ok, so it seems that we are going to go with OSB over a layer of plastic for a vapor barrier. We have researched closed cell foam and do not like the price for one or the installers in the area. Everyone just tries to treat us like normal homeowners and tries to bullsh*t us. We can cut costs with fiberglass batts and the installation will be free and we will know it will be done right. Other than foam, are there many other options?
You don't need and should not install a vapor barrier in New Orleans. Osb is fine there is so much humidity there you need drying potential in both directions. ------------------
"You cannot work hard enough to make up for a sloppy estimate."
first you need a vapor barrier on the floor due to the excess moisture in the ground and termites. most people just lay the vapor barrier on the ground. Insulation floor, less than 10% does that here, It just not needed. If I was doing it and I would, i would used either batts with plywood, or the stiff styrofoam and the spray foam to hold it
Thanks for all the information. This forum has been a great source of information for me in the past. Now that I have moved to the deep south, the building techniques are much different. I'm sure I will be posting many more questions in the future. Thanks again