Free polyiso

[PTFab]

I have the opportunity to get lots of free polyiso seconds from a manufacture. I’ve been reading the pros/cons on polyiso insolation and have begun to get a little worried if I should bother using it. I understand it can loose r value if it has been stored in a wet or in a humid invoroment, well I’m in the PNW and they have left it outside (who know how long) shrink wrapped so its hard to say the condition. (I can see holes in the wrapping) I would like it to insulate the ceiling of my future shop above the roof deck with 4’. Really can’t decide as it’s something that will be very hard to remove. Looks like it is one side Kraft. Seams like it would be hard to tape the seams for a air tight seal..

It will cost me some money to go get it as it’s a bit of a trip to get it.

Your 2 cents?

 

[tcianci]

I have seen wet polyiso but only on installations where the product had been under a bad rubber job for years. If it's cheap enough go for it.

 

[PTFab]

I should add that the piece are 4’ x 4’ x 4”. So layering and staggering may not be an option. But I have thought filling the joint cavities as well..

 

[Jon_E]

I used 2" thick polyiso w/ a fiberglass facing both sides. Cut it to fit my stud bays and used construction adhesive to stick it to the sheathing (Zipwall) on the inside. Then I sealed the cavity with spray foam. Mine was free for the transportation, I made sure to keep it inside for a few months to dry it out of any residual moisture before installation.

When you say 'above the roof deck' - will you be putting the material on the outside of the building? If so, it will have to be protected. This stuff is typically used on commercial roofs where it's covered with a 40-mil sealed membrane.

 

[chaosracing]

Depends on why its seconds. I worked commercial roofing for a few years. Some seconds have voids in the foam so there is already a reduced R factor. Sometimes its because the facer is not properly adhered to the foam (we used some like that under Ballast or Mechanically fastened roofs if possible) Sometimes its because it does not meet the R value required, so they scrap the entire lot rather than test it.

As long as its not the stuff with voids, I would grab it and use it, and yes, you can stagger the joints with it. As for sitting outside, as long at its not moldy or soaking wet, there are no issues, if it is damp or a little wet, just store inside if you can, with the wrap off and try to put some kind of spacer between the pieces so air gets to it. We would store partial used bundles out in our storage yard all the time and it got wet sometimes.