Friday, March 08, 2013

Building High Performance Walls, Working with stone wool

I came across a great series of videos on YouTube from a Swedish catalog house builder showing the insulation steps in completing their walls. This catalog house builder happens to work on site, not in a factory, so its particularly useful for American builders trying a Layered Nordic Wall system like USA New Wall building it on site.

This first video shows the primary wall cavity being insulated. Note how easily the stone wool is cut and handled, and how it friction fits into place without stapling. See that the insulation can be easily slid vertically to fit into concealed areas, such as behind the ledger for second floor joists as in Swedish Platform Framing.

Now in this second video they will be installing the horizontal furring, which in the USA New Wall forms the wiring chase. The astute reader will say "Hey, where is their vapor control layer? They are putting up the furring without it?" If so, good observation. The reason is that this manufacturer builds their wall a little bit differently. This first layer of horizontal furring is mainly to create a thermal break for the studs. After they insulate this layer of furring they will go over this with a vapor control membrane, and then a second layer of vertical furring that forms their wiring space.

This is actually a very effective system, because this second layer of furring is offset from the studs breaking the remaining thermal bridges where the first furring rests across the studs. They get a complete thermal break just like you do with continuous exterior insulation, but none of the complications with window frames and flashing details. Watch them do this in the next video. You'll see that they have a vapor control layer installed around the entire interior, walls and ceiling - interior partitions are not framed yet, only bearing partitions. So you can see how there is an air tight "bag" around the entire conditioned space.

And why is it that you are up on ladders putting adhesive tape all over your sheathing? Its much easier to do air-tight and vapor control at the same place.


  1. Very fascinating. I was unable to find a video however where they demonstrate wiring box installation. I understand the wiring chase idea, but I assume there will still have to be a box firmly mounted to the framing or the furring. It doesn't seem there is enough depth with the two furring strips to accommodate this ?

  2. Kent, look at this blog post:
    There are stills from a video which show the placement of electrical boxes, and the video is at the bottom.

    The answer is they use a plywood panel spanning between studs, or in this case between furring to mount their electrical boxes. This is not precisely the way we would do this here, instead we can rely on 4x4x1.5 boxes and mount to the side, or through the back - you actually have more mounting options than conventional construction.