Insulation, Radiant and Vapor Barriers - insulating basement walls
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08-03-00, 10:12 PM
I am not sure which is the best way to insulate my basement walls. I am using 2", R10 pink foam board. Should I use it inside or the outside for best results. I cannot afford to do both. I think its better to fight the cold on the out side befor it gets through the walls. I am not an expert please advise. Thank You Lewis
08-04-00, 10:21 PM
Hi Lewis,
We just had our cabin put on a new crawlspace foundation and have been researching this very question. You can put blue board (or a similar product) on the outside of your walls and then backfill against it to hold it in place. However, if any of it shows above the fill, then you'll have to cover it with T1-11 or something similar, since it can't be exposed to the sun. Also, contrary to what is advertised, foam board will pick up some moisture over time. Also, if you glue anything to it, be certain that the adhesive is a type that won't eat the foam. You'll also need to buy or fabricate some sort of flange that will attach in the area of your sill plate and divert the water from falling on the foam.
We looked at other options, too. Spray foaming the interior with Type 2 foam doesn't meet fire codes, so you can't put any heat producing appliance, such as a water heater there, unless you're willing to enclose it in it's own little sheetrocked room. Type 1 foam is more costly but safer and though it also doesn't meet fire codes, insurance companies recognise that it is safer. You can foam board the interior walls, but there's some cutting and fitting involved and I can't remember what the regs are concerning fire codes. We finally decided to hang backed fiberglass on the interior of our crawlspace, because it's fairly easy to do and you get twice the R-value for half the cost. Hope that gives you some more info to work with.
hatch
We just had our cabin put on a new crawlspace foundation and have been researching this very question. You can put blue board (or a similar product) on the outside of your walls and then backfill against it to hold it in place. However, if any of it shows above the fill, then you'll have to cover it with T1-11 or something similar, since it can't be exposed to the sun. Also, contrary to what is advertised, foam board will pick up some moisture over time. Also, if you glue anything to it, be certain that the adhesive is a type that won't eat the foam. You'll also need to buy or fabricate some sort of flange that will attach in the area of your sill plate and divert the water from falling on the foam.
We looked at other options, too. Spray foaming the interior with Type 2 foam doesn't meet fire codes, so you can't put any heat producing appliance, such as a water heater there, unless you're willing to enclose it in it's own little sheetrocked room. Type 1 foam is more costly but safer and though it also doesn't meet fire codes, insurance companies recognise that it is safer. You can foam board the interior walls, but there's some cutting and fitting involved and I can't remember what the regs are concerning fire codes. We finally decided to hang backed fiberglass on the interior of our crawlspace, because it's fairly easy to do and you get twice the R-value for half the cost. Hope that gives you some more info to work with.
hatch