Now What's Under Here?

 With a little help from Scott's kids, we smashed some holes in the old plaster and lath to confirm the construction of the existing house.  We had guessed it was going to be balloon frame with 1” pine sheathing on the outside, based on other renovations of houses around the same vintage.  It turns out that it is balloon framed, but has pine sheathing on both sides of the stud cavity.  This is another common method in old Ottawa homes.

So – the wall section is as follows, from outside to inside

Brick
Slight air gap
1” pine sheathing
True 2”X4” balloon framed on 24” centres
1” pine sheathing
Paper
Vertical lath (3/8 to 1/2”) on 12” centres
Horizontal lath at roughly 1/4” spacing
Plaster.

We had been studying several options for air sealing that involved using a 1-2” layer of closed cell foam – to minimize the use of foam, but still get its most important advantage.  However, with the sheathing on the inside of the stud bay, this would require us to remove most of these boards to spray the foam.  That seems like a waste of good structure to us (likely some additional bucks as well to remove those).  So – this is one more strike against closed cell foam for the project.  We are going to look at the Icynene pour-and-fill options for the cavity.  More to come on proposed wall sections and the latest challenge to get an R50+ wall, with low embodied energy, and still have room inside the house to live.