Poly iso foam board vs fiberglass

[Slimjim6100]

I'm getting ready to insulated the walls on my new pole building and not sure what to use. It's 32x40x13. Had it house wrapped when it was built to. I can get enough 3 inch poly iso for 1600 or 4 inch for 1800. If I use fiberglass it would cost me a little over 3 grand for r19 with all the lumber. My neighbor who builds garages for a living told me the 3 inch poly would be fine for it, it would also be alot less work for me to put it up instead of the fiberglass. Just don't want to regret not having enough insulation in the walls. I'm from pa and plan to keep it heated all winter with the in floor heat. So any advice would help me make the decision. Thanks

 

[jack stand]

Your last sentence is your answer.
That little bit of extra effort and expense now, will reward you forever especially with a radiant slab. Hopefully you insulated it to the same extent.
It's very hard to have much concern for insulation when it's miserably hot, being cold is a pleasant thought. Stick to your guns!

 

[mike93lx]

Would the poly iso go up in continuous sheets or need to be cut up to fit?

4" poly iso should be around R27, plus it would be continuous if the walls aren't studded, which is a lot better than all the thermal bridging from studs.

With that said, are you finishing the interior?

 

[Slimjim6100]

Would the poly iso go up in continuous sheets or need to be cut up to fit?

4" poly iso should be around R27, plus it would be continuous if the walls aren't studded, which is a lot better than all the thermal bridging from studs.

With that said, are you finishing the interior?

They would go between the 6x6 posts. They're 8 ft on center, it's not studded up, that's why I'd prefer to use the foam board as long as it wouldn't be an issue. I plan to add 2x4 girts across the posts on the inside and put metal on the walls