# Floor joist.



## wjjones (May 28, 2010)

Anyone have any advise/ ideas on the best way to easily insulate the void between floor joist from under the house?


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## pogobill (Jan 31, 2012)

There is a contractor installed spray foam insulation that is used a lot up in this neck of the woods. Watch Holmes on Homes on BBC.
You can also get bat insulation, but get the proper width to fit between the joists. Then I would think about stapling house wrap or something similar that is breathable to the joists to make sure the insulation doesn't fall out. I'm not sure if they still sell the paper wrapped insulation that had the stapling flange built in?
Just don't seal off the area under the house so that it is air tight, or one day your stove and fridge will end up under the house when the floor rots!


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## Hoodoo Valley (Nov 14, 2006)

Fiberglass insulation is going to be your cheapest option. Up here, we use a minimum of R28. Down there it would be something probably like R19 or 6 1/4 inch. I would use batts rather than rolled........... easier by far to handle! They make what we in the building industry refer to as "Lightning Rods" which are pre cut lengths of wire that bow into place between the joists on account of being slightly longer than the widths between your joists which will either be 14 1/2 for 16 inch centers or 22 1/2 for 24 inch centers.


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## wjjones (May 28, 2010)

tractor beam said:


> Fiberglass insulation is going to be your cheapest option. Up here, we use a minimum of R28. Down there it would be something probably like R19 or 6 1/4 inch. I would use batts rather than rolled........... easier by far to handle! They make what we in the building industry refer to as "Lightning Rods" which are pre cut lengths of wire that bow into place between the joists on account of being slightly longer than the widths between your joists which will either be 14 1/2 for 16 inch centers or 22 1/2 for 24 inch centers.




Yep ours are 16" on center. I have had to do repairs in a few places, and I wasnt sure what would be the best way to put the insulation back in, and secure it. I looked online, and its just confusing because they have so many ways they claim you need to do it. I just want to insulate, and seal nothing more. You are correct on the R factor usually this area is R19. I have noticed though alot of our heat loss is from the clothes dryer vent. I have a draft guard on it but it doesnt stop air like they claim it should.


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## Mickey (Aug 14, 2010)

Recently finished up my little shop project. Found out there is a BIG price difference between roll and bats for same (thickness & R value) insulation. Price difference is almost 2X.

One way I recall supporting insulation in the floor was to drive nails into the joists and string wire back and forth (zig, zag) between the joists thus holding up the insulation. This was yrs ago before bats were available.


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## Hoodoo Valley (Nov 14, 2006)

wjjones said:


> Yep ours are 16" on center. I have had to do repairs in a few places, and I wasnt sure what would be the best way to put the insulation back in, and secure it. I looked online, and its just confusing because they have so many ways they claim you need to do it. I just want to insulate, and seal nothing more. You are correct on the R factor usually this area is R19. I have noticed though alot of our heat loss is from the clothes dryer vent. I have a draft guard on it but it doesnt stop air like they claim it should.


Almost forgot too........ Use the unfaced (non vapor barrier) type insulation. Here's some photos of the wire ties I speak of. It's the best cheapest and quickest way to hang insulation in your crawl space.


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## wjjones (May 28, 2010)

tractor beam said:


> Almost forgot too........ Use the unfaced (non vapor barrier) type insulation. Here's some photos of the wire ties I speak of. It's the best cheapest and quickest way to hang insulation in your crawl space.




Yep thats the way I want to go right there. Thank you for the pictures Chris. Is there any need for a hard backer board to go on there to protect the insulation?


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