GBA Logo horizontal Facebook LinkedIn Email Pinterest Twitter 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

Roxul for insulating and air sealing finished condo

Greenscape | Posted in Energy Efficiency and Durability on


I am trying to decrease air currents and increase insulation in my finished condo. I have large floor to ceiling windows, old baseboards at the base of those windows, and a few columns enclosed by drywall around the perimeter. The columns are loosely filled with pink fiberglass insulation. Air currents are currently coming out of the base of some of these columns and also from beneath some of the baseboards.

Two questions:

– Would it be an acceptable solution to loosely spread Roxul RockFill inside the columns via the wall outlets to at least try to cover the base? One concern I have is that they are already filled with pink insulation, and I have been told that air current is actually necessary for this kind of insulation to work.

– Would tightly Packing Roxul RockFill into the crevices and gaps around the base of the columns and baseboard serve as an appropriate solution for air sealing and insulating?


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, it is not true that air currents are necessary for fiberglass insulation to work. Air currents degrade the performance of fiberglass insulation.

    Roxul mineral wool is not an appropriate material to use for air sealing.

    To seal air leaks at your baseboards or other cracks, use caulk. You can either choose a caulk that matches the color of the baseboards, or you can buy clear caulk. You can caulk the crack between your finish flooring and the baseboard, and you can also caulk the crack between the baseboard and the drywall.

  2. Greenscape | | #2

    Thanks for the quick reply. So would it be okay to try to fill the drywall with Roxul RockFill in addition to the fiberglass that's already there?

    Regarding the caulk, some of the gaps are empty cavities that would not be properly sealed by caulk. Would very tightly packing the larger cavities with Roxul work? I don't necessarily have access to the source of the air currents without opening up my drywall. I only have access to the mouth of the cavity, which I could fill with something (Roxul?) without going through drywall.

  3. GBA Editor
    Martin Holladay | | #3

    Green Scape,
    I can't visualize the cavities you are describing. (Perhaps you can post some photos.)

    If there are cracks that are too wide to caulk, the usual method of air sealing is with canned spray foam. Of course, once the foam has cured, you don't really want to look at it.

    If you want to fill cavities behind your drywall with insulation, you have to either (a) remove a section of drywall, or (b) drill a 2-inch diameter hole in the wall and blow in some cellulose or blown-in fiberglass insulation (using an insulation blower).

Log in or create an account to post an answer.


Recent Questions and Replies

  • |
  • |
  • |
  • |