I recently had a spray foam contractor give a quote to inject foam into my home. The house is brick, built in 1940s, and is in Ohio. The contractor said because of the type of construction, he could not guarantee injection into the stud bays/cavities from the outside. Because the house is plaster and wire and the need to drill holes, I told him injection from the inside was not an option (he said that wouldn't do it anyway because it would a huge pain in the a**. I agreed). He said that injection from the outside into the cavity between the wall sheathing and brick would be an equally useful option. I've done some research on this, and its getting pretty negative reviews due to the foam disrupting the vapor/water interface inside of the wall. Any thoughts/advise would be appreciated.