General insulation question

[knightryda01]

So I have a steel pole barn located in Michigan, and I insulated the walls with foam board and styrofoam. I have yet to do anything with the roof. What would be the outcome if I just put up a styrofoam ceiling attached directly to bottom of rafters? Located in Michigan so we can have cold winters. Would steel sweat alot from temp changes etc.

 

[knightryda01]

nobody?

 

[850xpeps]

The steel will sweat if warm air gets to it in the winter. To the point it can be like rain. So you need to seal off your conditioned air from getting to it. I’d reccomened an air space between metal and insulation and then vapour barrier under that.

 

[strutaeng]

On the walls:

1. Did you apply the full sheets on the face of the girts, as in what they call continuous insulation (CI)?

2. Or did you cut between the girts, sometimes called "cut and cobble?"

Option 1 is always preferred because it forms a continuous thermal barrier, like an Igloo cooler. Assuming you have enough insulation you should not have sweating. It is best to do at least 2 layers of rigid insulation and stagger or offest the joints. I did 7" in 3 layers of CI to a portion of my house. 1" XPS + 2 layers of 3" Polyiso. In my case the insulation is above the roof deck, but can also be installed below. Temps here get in the teens sometimes in the winter and this has worked well for me.

I hope this helps.

There is a lot of useful information on GreenBuildingAdvisor.