Does not trap moisture behind it. It has enough holes and slots built in to allow the house to vent. Hardi-Plank (a concrete product) will absorb some moisture, but will also allow the house to breathe. Being a concrete product, I would be surprised if you really have to paint it at all except for visual reasons. I think this decision boils down to what you think looks better on your house. If you are a do-it-yourself person, vinyl is also easier to work with. Just my opinions, Dodgeman