Insulating a floor during construction

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Old 11-06-18, 08:30 PM
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Insulating a floor during construction

Hello all,

I'm constructing a 620 square foot home addition with a pier and beam foundation in South Louisiana. I'd like to insulate the floors with fiberglass batts, and it would obviously be easiest to do that before laying down the subfloor. My concern is that, given my location, the subfloor will almost certainly get rained on before I get a chance to black-in the addition. The subfloor is 23/32 t & g plywood which will be glued and nailed. Is my only option tarping the addition each day until black-in is complete?

Thanks in advance,
Peter Youngblood
 
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Old 11-06-18, 10:37 PM
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Hi Peter, I have a question, what is going below the fiberglass? FG is not the best insulation and if not enclosed on all sides it gets worse.
Then, what is under the house? I'm not a post and beam guy so picturing a house without a foundation, open underneath?? If so, any access from below?

Watching the elections so I'll leave the rest to the pros in the morning.
Best,
Bud
 
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Old 11-07-18, 09:45 AM
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Bud,

The crawlspace will be skirted with lattice and hardware cloth to keep critters out, so it's technically an open crawlspace. On the ground under the addition is 6mil poly to act as a vapor barrier. I've seen others use fiberglass in the floor around here, but I've never used it myself. Seems like a real pain to install after the subfloor is down. I'm sure blown-in or spray would be easier, but the latter is probably not in the budget.
 
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Old 11-07-18, 10:51 AM
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If the fiberglass insulation is open to the space below that needs a solid air barrier, osb or plywood. That will improve the function of the insulation and keep a multitude of insects out.

You didn't mention how much clearance you have below the floor joists. In some areas there is a minimum.

From above you could install strips at the bottom inside of the joists to allow pieces of plywood or osb to be dropped onto place. Then fill or install insulation on top of the plywood. Gap at the top is an option as I doubt you have a lot of cold weather.

Bud
 
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Old 11-07-18, 11:14 AM
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To keep rain out get the widest roll of poly you can find and roll it out over the top of your subfloor once it's down. Tape any seams. Frame all your walls on top of the poly. Once your roof it on you can cut the poly off.

If you can squeegee off the water with a floor squeegee after a rain that will be helpful.
 
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Old 11-07-18, 06:47 PM
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Thanks again. My joists are about 21" above grade. We don't have much cold weather, but still enough to make floors chilly.
 
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