"mdb" wrote in message
news:T30Ah.1219$yg7.240@trnddc08...
Yes, the construction is all masonry. Brick facing with a block core.
Plaster lath attached to the block interior surface. The only voids are in
the blocks. I did go up into the attic to see if I could see any leakage
issues. Nothing. Nor is there any obvious leaking happening on those
interior walls. It's the entire cold wall surface where the original paint
flakes away from the skim coat. So I don't think injected insulation is an
option for me.

If the top of the block is accessible, it is possible to insulate the holes.
Not a cure all, but it does help. This is often done on
commercial/industrial block buildings.