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A2diyfamily
Rim joist insulation options

Any recommendations or suggestions for replacing the existing rim joist fiberglass batt isulation that is in poor condition on our 1914 small home? Is there a DIY expanding foam option with good R value that is reasonably priced and readily available?

canuk
Re: Rim joist insulation options

Using rigid foam insulation is an acceptable and very good solution for this.

Cut to fit and seal the joints well with either caulk or spray foam in a can.

Hope this helps. :)

jdawg
Re: Rim joist insulation options
canuk wrote:

Using rigid foam insulation is an acceptable and very good solution for this.

Cut to fit and seal the joints well with either caulk or spray foam in a can.

What about fire code? I've read that exposed foam is a fire hazard and is required to be covered w/ 1/2" thermal barrier, i.e. drywall. This would be a royal pain in the you -know-where! Any thoughts? Appreciate it!

Mastercarpentry
Re: Rim joist insulation options

Codes vary so you have to see what is required wherever you are at. Yes, foam will burn but so will wood and nobody is suggesting that wood floor joists and underlayment are fire hazards in residential home construction. It's all an assessment of real risk, possible risk, and risk mitigation techniques. And some is based on economy. The fiberglass failed from moisture- the foam never will. At the foundation level, fire risk mitigation is focused on containment so that a fire there does not spread upward- that part is not going to be significantly changed by the insulation type installed at the rim joist. Few home fires (if any) start or are significantly affected in this area so I wouldn't worry about that- I'd go with foam so long as local codes allowed me to and all I would expect to happen is for me to never have to do the job again.

Phil

sauron
Re: Rim joist insulation options

You can buy pink XPS foam in 1" to 2" widths and use PL300 adhesive to attach it. I used the spray foam to seal around each piece (I did this in between the floor joists).

canuk wrote:

Using rigid foam insulation is an acceptable and very good solution for this.

Cut to fit and seal the joints well with either caulk or spray foam in a can.

Hope this helps. :)

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