Insulating a metal roof?

[bwat]

Need advice on the best type of insulation for a metal roof shop. Is there something between batted fiberglass home center insulation and the industrial building variety?

Rafters are 2x6 topped by 1x4 perlins then sheeted metal roofing. With batted fiberglass I'm limited to R-19 which is 6 1/2" thick. The interior of the ceiling will be enclosed with sheet goods and painted.

I've seen the metal reflective products out there but haven't seen any greater R value although they may be better for any dampness from condensation??? Think I need to find a roofer for advice. Thanks for any suggestions.

 

[scsmith42]

The very best insulation is spray foam applied directly to the bottom side of the skip sheating (purloins) and tin.

The spray foam prevents any type of condensation buildup, and has the highest insulating value.

I did this in an old farmhouse a few years ago and the effiency is incredible. Plus, the foam dampens out the noise from heavy rains on the tin roof.

 

[Jim M.]

+1 for Spray Foam. I used it in my shop, keeps it nice and cozy. Jim

 

[bwat]

Has anyone tried the DIY kits for the foam insulation? I haven't found anyone that stocks them locally but they are available online.

 

[Jim M.]

I haven't used one of those kits. But I saw a DIY kit being demonstrated on HGTV a while back, that's when I became interested in it for my shop. As luck would have it they were building some houses behind me when I saw they were using the spray foam. I talked them into coming over (cash is king) and coating my shop before I buttoned up the walls and ceiling. Jim

 

[woodworker2000]

Has anyone tried the DIY kits for the foam insulation? I haven't found anyone that stocks them locally but they are available online.

You should calculate how much of the spray foam you need using their online calculator and compare it with a local quote. When I did it, I was shocked at the cost, especially when I compared it to a quote for having someone locally do it for me. If your job is large enough, I think you will find that the price difference between doing it yourself and hiring it out is just too small to take the risk of doing it yourself.

 

[jdulaney]

I personally would not do the whole building with foam, just under the roof. Too much sealing and the building can't breath, causing rot.

 

[scsmith42]

I personally would not do the whole building with foam, just under the roof. Too much sealing and the building can't breath, causing rot.

This is something new to me; can you elaborate?

In a modern, air conditioned building, because the AC will remove excess moisture, I'm scratching my head trying to figure out why it would rot?

Thx.

Scott