[Greenbuilding] Inserting insulating foam between brick layers?

[Alan Abrams]

<Dear all,

Does anyone have expertise/intelligent thought on the idea of spraying
expanding insulating foam between the two layers of brick in my 1860s
brick row house?

I'm about to do a major repointing job on the mortar, and realize that if
I want to do it, now would be the time, as it will be easy now and harder
afterwards.>


hmmm, was this a usual practice to leave a space between wythes?  the late
19th century row houses I'm familiar with in D & Baltimore have multiple
wythe walls, but they are laid up tight and bonded without any voids.

regardless, these bricks are likely to be very soft and porous compared to
those made in oil fired kilns in the early 20th century, or gas fired ones
of post WWII.  They are prone to spalling, particularly when pointed with
modern Portland based mortar--the original mortar was likely just lime and
sand.  When the bricks get wet, they swell, and a Portland mix will not
yield, so it blows the face off the brick.

Similarly, assuming there is a cavity that could be insulated, it would be
prudent to think through the effect of interrupting water vapor migration
through the wall, and whether it would exacerbate a condition in which a
saturated brick of the outer wythe, exposed to dropping temperature, would
freeze and expand while the warm and dry inner wythe remains stable--and if
so, would some differential stress cause mischief.

-AA