Subscribe to Fine Homebuilding magazine now and save up to 52%
This calculator also ignores the most common type of attic insulation in the northwest - blown-in fiberglass.
Why was fiberglass left out?
© 2016 The Taunton Press, Inc. All rights reserved.
Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features.
Start your subscription today and save up to 52%