Polly styrene and fibre glass and air expansion

I have just read where the fiberglass will separate in a hull made with epoxy and Styrofoam construction.If left in the sun this problem will occur. As I haven't started my build so this problem will have to be investigated and a solution found. Preliminary thoughts would be holes drilled threw to styrene and some sort of relief valve made. Polystyrene will absorb water over time to some extent and there in lies the problem.
This decontamination could adversely affect the overall strength of the end product.
Any thoughts would be most welcome. Cheers Iggle