Blue 2" Foam Board

[Dugan]

I might be able to get some 50 sheets of 4x8 Blue 2" thick Foam board to insulate my 30x40x14" garage.

Is the rigid insulation worth it? The price the guy wants is 25$ each, but im gonna try to get them all for 20 each. They are not foil backed.

Would putting these against the metal walls and then OSB over the top be a good setup? Would I need to put plastic between the insulation and OSB? I live in delaware and we have all 4 seasons, so its hot in the summer and really cold in the winter.

 

[Radix2]

The price per sheet is obviously good, but at R-10, is that a total solution for your needs? Is this to be a year round conditioned space? What is your construction, what space do you have to hold insulation?

 

[Dugan]

The price per sheet is obviously good, but at R-10, is that a total solution for your needs? Is this to be a year round conditioned space? What is your construction, what space do you have to hold insulation?

Its a 14' pole barn with trusses 4 ft apart on the ceiling. Spacing on the side walls is 8' between poles and the faces are 10' between poles.

 

[classic boost]

don't get hung up on the r rating. r10 foam sheets will do a great job. that's 32sq ft each of no heat breaks.

 

[COBRA5LADDICT]

i love XPS. that is a good price

 

[Bondo]

Ayuh,.... I bought a bunch of 2'x4'x4" dow board to put under my concrete floor at just under $5. a piece,....
I thought I did ok,....

I'd think the foam oughta work ok,...

Plastic,..?? I would, even if ya get the foam in place, tight, 'n sealed,....

 

[Voi]

I might be able to get some 50 sheets of 4x8 Blue 2" thick Foam board to insulate my 30x40x14" garage.

Is the rigid insulation worth it? The price the guy wants is 25$ each, but im gonna try to get them all for 20 each. They are not foil backed.

I don't remember what I paid for 2" blue rigid this past summer but I think it was around $30. So $25 is decent if it's been stored well. I've seen some overstock foam leftover from construction sights that was in rough shape. But it sold for around half price, IIRC.

Would putting these against the metal walls and then OSB over the top be a good setup?

Metal exterior walls? So you'd cut the foam to get between studs (in the case of stick built) or between the girts (in the case of post frame)?

Or do you mean something else?

I am not a fan of cutting foam to fit between framing members unless space is at a premium. It's boring work and doesn't take advantage of the foam's ability to act as a thermal break over framing members. It will also take a lot of canned spray foam to get a good seal and that adds up quickly.

But I'm making assumptions here. Post some pictures so we have a better idea of your project.

 

[86turbodsl]

Rigid foam tends to be better used where it can be structural, or to fully insulate without heat conduction through studs. I use it for things like under concrete, or building super insulated structures. It's pretty expensive as an insulation. I think i paid $18/sheet in 2007 for my house. It's also mostly oil, so with the price of a barrel continuing downward, it might continue to get cheaper for a while.
Overall, there are cheaper forms of insulation. I found spray foam sometimes to even be cheaper.

 

[classic boost]

It's also mostly oil, so with the price of a barrel continuing downward, it might continue to get cheaper for a while.

you would think, but it's only getting more expensive. it's ~$30/sht now.

 

[86turbodsl]

Cant last forever. Its a commodity like any other.

Sent from my SM-N910T using Tapatalk

 

[classic boost]

oil is the commodity not the foam. oil has been in the tank for over a year, and the foam price keeps inching upwards. dupont, 3m, whoever, is just laughing all the way to the bank.

 

[finn]

I've used it to insulate the slab and crawl space walls (wet locations). but would rather use bats or spray foam for most other locations.

Foaming / taping the edges is required in my opinion because the rigid foam is succeptible to air leaks, as it isn't conformable and is a poor insulator if there are air leaks around the edges. It works ok over the studs, where you can easily avoid fit problems.

 

[DC73]

One layer of this foam is not enough insulation for your climate but it's a good start. Before installing plastic (or any other vapor barrier) check with the experts on the Q&A forum at GreenBuildingAdvisor.

DC