To use or Not - Vapor Barrier for Brick House
NEVER use “expanding spray foam” on brick walls for four reasons: 1) expanding foam could put stress on the brick and crack the brick or the mortar joints, 2) too much insulation on brick could block heat transfer to bricks and cause the brick to crack, 3) moisture could get trapped in the brick, and 4) joists embedded in the brick wall could rot causing structural decay. 

1) Spray foam is acceptable (and may be the best choice, although expensive) but EXPANDING SPRAY FOAM will crack the brick or crack the mortar joints. Rigid foam is acceptable, but must be carefully installed so as not to allow moisture to transfer into the wall, freeze and then crack the wall. 

2) currently, warm moist air transfers into the brick and keeps the brick (and moisture) from freezing. Thickness of insulation must be considered so as not to make the inside of the brick too cold, freeze and then crack the brick. 

3) you’ll need to determine if the type of brick will “absorb” moisture. Any moisture transferred from the exterior into the brick or any moisture transferred from the interior (via dew point) could freeze and crack the brick. 

4) If joists are embedded in the brick, adding insulation could make the ends of the joists (on the cold side of the insulation) rot. 

Some bricks are more vulnerable than others to freeze/thaw problems. This usually has to do with permeability. The thicker the insulation the greater the chance of cracking the brick wall during extremely cold times.