should I use foam board on roof?

[cutthroatxxx]

Quick question,I'm as you may or may not know insulating my 24x36 shop with 1&1/2 white foam board the shop isn't set up like a traditonal pole barn it has the concrete floor of course&then 4x4 every so often then 2x4s to complete the framing&is sheeted with osb the roof instead of a gable roof or barn roof,its a pitched roof like you would see on a lean too or some just call it a shed roof.Well the rafters are every 4 feet with 1x4 cedar runners someone told me not to put the foam board up there to just use the plastic since the roof is so low,my plan was to put the foam between the rafters attached to the runners.The last 12x24 section of the shop I really don't use it has a seperate room that is 12x8&the other part that's open is just shelves with motorcycle &car parts so I was gonna block it off with a tarp or moving blankets as a tarp as another member suggested.What do you guys think?

 

[rkevins]

I would have put the insulation on top of the lath then tar paper then the sheet iron, but sense the top is allready on. I gess you could put the insulation under the lath I would use screws and fender washers to hold it up. It looks like your lath are staggered was there a reason for that we allways just let them join on top of the rafter

 

[Lippyp]

If you're talking about the solid expanded PU foam board with the silver backing then go for it, I'd cut it a nice tight fit between the rafters and it will largely hold up by friction, if it needs some help then screw/nail a batten to the rafter below the foam board, tape the joints with silver foil/mylar tape. It helps to leave an airgap between the insulation and tin to help dry out any condensation that may form on the tin and the runners you have will naturally give you that space.

 

[darkk]

If it were my shop, I'd insulate all the ceiling/roof area with as much as I could stuff up there. keep it cool in summer, warm in winter.

 

[Lippyp]

My last garage had a tin roof much like that and it was freezing in the winter much so it used to get ice on the inside of the roof and like an oven on a sunny day in summer so I'd consider insulation a must for a tin roof.