Spray foam vs DIY Roxul

[nick123]

Hey everyone,

Just want to get some input. Slowly but surely insulating this house. I opened up an exposed porch ceiling and found a cavity with un-insulated walls walls and floors. Got a quote of 1200 for closed cell foam (3 inched on walls and 4 inches under floor). Also considering going DIY and using foil faced board and r 15 roxul on walls/ foil board and r-23 roxul on under exposed floors. I would be insulating the walls from the back side hence why i'm using foam board vs regular vapor barrier. Would I get a better result with spray foam?

Thanks Nick

 

[xman23]

Sorry I can't directly answer your question. I was at a high rise building site that was spraying all the exterior wall cavities. It really seals everything in the wall. It looked like a simple process. If you are doing a lot of it you might be able to buy or rent equipment to do it yourself.

A comparison of the "R" values of each would be where I would start. It would be hard to seal the boards to be as tight as the spray. Any issues with insects getting in this stuff?

 

[nick123]

No insect issues...

 

[moey]

Whats the cost difference? I suspect you may only be saving a few $100 bucks.

 

[nick123]

I would be saving about half...

 

[jeffesonm]

Check the Green Room forum, lots of insulation threads over there.

 

[moey]

Id lean towards the spray foam assuming its no additional work on your part. Insulation has to be done very well to actually achieve the R value stated. Ive been adding insulation in my basement XPS glued on the walls with drywall ontop. Its a slow process and very tedious. I would have opted for spray foam but I didnt want to have to put up 2*4's and then drywall I have lots of obstructions as well that can not be moved for someone to spray.

 

[gzecc]

I would be most concerned about preventing ice daming with what ever you choose.

 

[Wisneaky]

I did most of my house regular paperback insulation, but we had our crawl space done with spray foam. If I had to do it all over again I would of did it all spray foam. Even though on the exterior walls we have a vapor barrier you can still feel a draft on windy nights. With the foam nothing comes through at all.

 

[brenndatomu]

Got a quote of 1200 for closed cell foam (3 inched on walls and 4 inches under floor)

Not sure how many sq ft you had quoted but I had ~1800 sq ft of open cell (IIRC) foam pumped into my 2x4 stud walls for $2400.
It was a big improvement over nothing but I overlooked the 2% shrinkage that they openly admitted would happen as it cured...2% of a 14.5" stud cavity is actually a pretty good gap, so much for the air sealing advantage of "spray" foam.
If I had it to do over again I would have went with cementacious foam (Air Krete is the local brand) at about twice the cost. All the same advantages of regular foam plus,
mold proof
fireproof
0% shrinkage
better sound proofing
no toxic off-gassing
Bug/rodent proof
no settling
higher R value than foam
not future hazmat waste (green)

My 2 cents...

 

[Bret Chase]

If I had it to do over again I would have went with cementacious foam (Air Krete is the local brand) at about twice the cost. All the same advantages of regular foam plus,

I built a cellular concrete rig for a local company this past spring... while this was for geotechnical uses, the concept is more or less the same. neat product....