I would like to insulate the sides of a shed which was built with a damp proof membrane (not breatheable) between the T & G cladding and the 3 x 2 frames. This ensures watertightness but, if I add insulation and then put another DPM on the inside, then any moisture would have nowhere to go.
Is there a solution to this problem? Should I make small perforations in the waterproof membrane to allow evaporation?
Any suggestions gratefully received.
Julian