GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter X Instagram YouTube Icon Navigation Search Icon Main Search Icon Video Play Icon Plus Icon Minus Icon Picture icon Hamburger Icon Close Icon Sorted

Community and Q&A

I live in the Northeast and have ice dam issues

takvorr | Posted in Energy Efficiency and Durability on

I am having the attic insulated. I am getting conflicting answers re the attic joists. Should they be sealed and insulated? One contractor says no as needs to stay cold to prevent ice dams. Another says yes should be sealed and a radiant barrier added then blow in insulation. Who is right?

GBA Prime

Join the leading community of building science experts

Become a GBA Prime member and get instant access to the latest developments in green building, research, and reports from the field.


  1. GBA Editor
    Martin Holladay | | #1

    First of all, do you mean joists (the framing members on the attic floor) or rafters (the sloped framing members that define the roof plane)?

    All buildings need either ceiling or roof insulation. In most areas of the country with ice damming problems, the minimum R-value for this insulation (according to most building codes) is R-49.

    The insulation can either be installed on the attic floor or along the roof slope. Either way works, as long as the details are correct.

    If you choose to insulate along the sloping roof, you can either create an unvented roof assembly or a vented roof assembly. To learn more about insulating this type of sloped roof assembly, see How to Build an Insulated Cathedral Ceiling.

    To learn more about preventing ice dams, see Prevent Ice Dams With Air Sealing and Insulation.

    If you are a GBA Prime member, you should read Ice Dam Basics.

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |