Which XPS foam board?

[Bradbilt]

Which foam board?, EPS or XPS?

I have been looking at Ownes corning XPS 2" foam board for under my concrete floor in my new garage.

Which one should I go with? The 250 rated at 25psi or the 150 rated at 15psi?
other than that I can find no difference between the 2

but there there are confusing articles saying that I should use EPS because it it much cheaper, retains its R value better, etc

 

[rooster4321]

Are they the same R-value

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[Bradbilt]

Are they the same R-value

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Yes the 150 and 250 are both r-10

 

[ConCretin]

You can use either XPS or EPS as long as it meets ASTM C578. Most will opt for the higher compressive strength of the 25 psi for under slab use. I've read some of the studies about the long term performance of the EPS but XPS is more commonly spec'd on commercial work. Give my Guide to Floor Slabs a read for some additional thoughts as you proceed with your slab.

 

[Bradbilt]

You can use either XPS or EPS as long as it meets ASTM C578. Most will opt for the higher compressive strength of the 25 psi for under slab use. I've read some of the studies about the long term performance of the EPS but XPS is more commonly spec'd on commercial work. Give my Guide to Floor Slabs a read for some additional thoughts as you proceed with your slab.

Thanks. I have read your guide and it is VERY helpful.

Both meet the c578 rating

 

[Viper98912]

While I'm not an expert, the 250 is listed to be used under floors (for it's compression strength) whereas the 150 is for walls