SIP structurally insulated panel

[fasboater]

I am looking at an SIP for the roofing on a residential home.

I have read many different opinions about the moister barrier (ice and water shield) and venting the deck.

My situation is an 8” Sip for the roof with screw down metal standing seam. Obviously the possibility of leaks and all that concern me.

Question:

1)Would I apply a moisture barrier (ice and water shield) directly to the SIP and then put some hats or furring strips over that for the Standing seam? Creating a vapor barrier does the the SIP need to breath?

2)Would I add another layer of plywood over the hats or furring strips and then put my vapor barrier down (ice and water shield).

http://www.bowerseng.com

 

[shobroco]

I'm not a big fan of SIPs, but that aside, ice & water is really a belt & suspenders approach to metal roofing, and a double vapour barrier on your insulated assembly. If you need it under the metal, you have a lousy installation. However, you do need tarpaper or tyvek because no matter what the SIPs manufacturer & installer tell you, you are going to have some warm moist air escaping through them & there are times when you are going to have condensation on the underside of the metal. Assuming that the SIPs are waferboard, that means a pile of loose wood flakes at some point down the road if they keep getting wet. I'd say a good installation of 15# felt & a proper metal roof installation directly on it is the way to go. Just for reference, my house is 20 years old, has a metal roof on tarpaper on a fully insulated unventilated roof that I did after pricing SIPs & deciding that I was happy with 50% more insulation for 50% less cost. I have watched closely for years without ever seeing any moisture issues and have since relaxed about it despite all of the Cassandras saying you have to ventilate. You don't have to ventilate if you have a very tight envelope and a way for moisture to dry to the exterior if it gets into your system.

 

[MiketheEngineer]

What does the SIP mfg say?? and does he have test results to prove it. If not - find another SIP mfg. There are actually some good ones out there and SIP's do have their place!!