UV rays from the sun are quite destructive to foam and fabric. Heat will also age foams. When some foams get old they get hard and brittle and start to crumble and turn to powder. I recommend replacing them.

I noticed that the foam cushions on two indoor chairs are incredibly stiff, as well as the velour (velvet-like) fabric appears some-what faded and not as smooth in texture. The two chairs were routinely placed (and left outside).

My question is, what causes the foam in the cushions to become very stiff? Are they considered damaged at this point?