Insulation Between Floor Trusses

Old 07-06-19, 05:12 PM
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Insulation Between Floor Trusses

I am finishing my basement and am using R30 unfaced fiberglass rolls in between my floor trusses as a sound barrier. My question is, what is the best way to get the insulation to stay in between the floor joists?

The issue is because of my truss spacing and because I have floor trusses and not TJIs, the insulation won't stay up by itself. The majority of my trusses have an open space between the trusses of 20.5" with some having an open space of 16". The roll of insulation is about 15" wide uncompressed.
  • My first attempt was to cut the insulation a little longer than 20.5" and compress it in, but it would just buckle and fall down.
  • My next attempt was to cut one roll in half, full length and use it with another full roll. This worked OK but was being held up by electrical wires and plumbing. My goal was to have the insulation up against the bottom of the OSB sheets to leave open space below in case I ever needed to run anything above the ceiling.
  • I modified the above technique and used straps to run perpendicular to the floor joists placed 8" below the OSB sheets. This works better but is very time consuming and still not great.
  • My next thought was if I could find some long nails (6"-8") and push them through the insulation and hammer them a few times in the OSB sheets. I am nervous that this might cause problems with the main level flooring.
  • I read somewhere to use chicken wire, but this would place it all at the bottom again and would probably be more time consuming and expensive than the other methods.
  • They make insulation supports out of wire but this wouldn't work well with the trusses unless I place them at the bottom of the floor truss.
I appreciate any thoughts anyone might have on the above methods or other options. Should I just be content with laying the insulation right over the wires and plumbing? Thanks.
Old 07-06-19, 05:47 PM
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I think I would be stapling up some insulshield fabric, then blow it full of fiberglass.
Old 07-07-19, 04:05 AM
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Along the lines of XS, how about strips of Tyvek, about a foot wide stapled to the bottom of the joists every 3-4 ft!
Old 07-07-19, 04:09 AM
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In my house I used insulation support wire. It's sold just for the job. You start putting the insulation in place then insert a wire between the trusses every couple feet to support the insulation. They also sell netting and fabric that can be stapled to the bottom of the trusses to support the insulation.

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