[Greenbuilding] Inserting insulating foam between brick layers?

[Stephen Young]

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.

I'm considering poking holes through the mortar every few square feet,
and spraying in as much of the insulation as will go. There is a gap of 1
- 1.5 inches between the outer brick and the inner brick.

Is this a bad idea? Does there need to be air flow btwn the layers?

Note that, inside the brick, I already have 1.5 inches of
polyisocyanurate btwn framed metal studs below the drywall, so this may
be overkill, but I just think it's a cool idea!

Thanks for whatever advice folks can give!

Stephen