Edit post

Edit your reply below.

Post Body
Enter your post below.
Not sure where you're located but you can achieve an R value of around 20 by using 2 layers of 2" foam in your existing roof framing. Up in the north, we design for a minimum of R30 in the roof of a house, but for the conditions you describe R20 might be adequate. We can get it in 2'x8' sizes which makes it handy for putting between rafters. The depth of the airspace isn't critical and more isn't necessarily better. With a standard 2x6 rafter, you should have 1 1/2" left after installing 4" foam which is more than enough. A 1 inch space is plenty. Make sure you get the right foam, though. The pink or blue foam is for insulation, has a higher R value and has fire-resistant properties. The white foam, or beadboard foam, is what they make coffee cups out of, has a much lower insulating value & is much more dangerous in a fire. Wayne
Tags (Optional)
Tags are keywords that get attached to your post. They are used to categorize your submission and make it easier to search for. To add tags to your post type a tag into the box below and click the "Add Tag" button.
Add Tag

Update Reply

Login, or register today to interact in our online community, comment on articles, receive our newsletter, manage your account online and more!

Model Railroader Newsletter See all

Sign up for our FREE e-newsletter and get model railroad news in your inbox!