I have some clients who renovated two of their 2 unit rental building a few years ago. The town insisted they use closed cell foam on the walls and roof plane but did not insist on any ventilation. The occupants are now experiencing stale air, odors, high moisture etc.

They’d like to install some ductless ERV’s to try and remedy this. From what I can tell most of the ductless options available are designed for pretty thick walls. This building has a 2×4 wall. Does anyone know of any good low profile units or a way to make the longer units finish out a little nicer. Because these apartments are small there will be limited options to locate these and I’d hate to have it look anymore awkward than it already will. 

Thanks