Replies

1. GBA Editor
   Martin Holladay | Aug 04, 2013 04:59am | #1

   Jessie,
   Your wall can easily support the weight of the insulation, in my opinion. The real concern is not really the weight of the insulation; it concerns the limits of the screws holding the furring strips.

   For more information on this type of calculation, see Fastening Furring Strips to a Foam-Sheathed Wall. If you remain concerned after reading that article, you can always consult an engineer.

2. 
   LucyF | Aug 04, 2013 09:26am | #2

   Jessie,

   Patrick Walshe has a blog where he writes about building a house with Roxul Comfortboard - A Green Hearth (I can't look up the link right now). Also one blog post specifically talks about the flashing around the windows.

   We are thinking about using "Dudley Boxes" for detailing around our windows. Foam outside of the rough opening, Dudley boxes taped to the foam, then roxul abutting the foam.

   Search for Dudley boxes on GBA website.

   I hope that helps a little bit.

3. 
   LucyF | Aug 04, 2013 10:40am | #3

   I found the links:

   Here is the link to window flashing with Roxul Comfortboard on "A Green Hearth" http://agreenhearth.com/our-lessons-in-window-flashing/

   Guest blog on exterior roxul insulation - https://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/installing-roxul-mineral-wool-exterior-walls

   Dudley boxes link - https://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/window-installation-tips-deep-energy-retrofit

4. 
   albertrooks | Aug 05, 2013 08:41pm | #4

   Jessie,

   Here is a design we did based on 6" of Mineral Wool on a wood framed wall using Heco Topix Therm screws. They are made for exterior insulation applications of 4" to 12" (which is still a bit novel in North America).

   It's pretty simple to get an evaluation done by a Heco engineer. Contact us at The Small Planet Workshop if you'd like detailed help on your application.

   
5. 
   LucyF | Aug 06, 2013 09:29am | #5

   Jessie,

   I was wrong about one of the details. Dudley boxes are useful for a retrofit with replacement windows. We are using wood windows with aluminum cladding so we will be detailing around the windows similar as described in the "A Green Hearth" blog.

   The main problem with Roxul as an exterior insulation is that you can't tape the weather resistant barrier to it so the windows will be "faced" with foam for the flashing details.

   We are also planning on using the Heco Topix Therm screws for fastening the Roxul, but we're only putting on 2 inches of the Roxul.

   Let us know how your project is going.

6. 
   415irwin | Sep 02, 2013 09:46am | #6

   Thanks everyone. Lucy have you begun installing your windows? One of the tricky parts of this process is integrating the window box details (sloped sill for example) with the window. We haven't chosen a window yet. The detailing is highly dependent on the window brand. Lucy which window have you chosen?