Hi-

 

I’m in the process of replacing some built in air conditioners with mini splits and so for the first time since buying this house I’ve had a chance to see a cross-section of the wall assembly. From the inside out:

-drywall

-plastic sheeting

-frame and insulation

-1/2 inch plywood

-1/2 inch OSB planks installed they overlap (Lapstrake?)

-1/2 inch foil backed foam board

-siding

Please see picture attached.

 

My questions:

-Is the way the OSB installed a good technique? I assume it’s so it can dry?

-How good/bad does this assembly seem with respect to efficiency? I’m trying to get a feeling for whether or not retrofitting the wall assembly would be worthwhile (my wife really wants to replace the siding anyway).

-I found water damage around the cut out for the AC unit. I’m assuming there’s water damage around the windows too, because the siding is installed the same way around the windows. The top molding/casement piece of the sidings (not sure that’s the right term) is not sealed/caulked, so water just collects that and drips around the windows. Six inches of the OSB around the AC unit hole was reduced to mush. Does this warrant immediate attention? Would this affect the efficiency of the walls?

Thank you!