Gas Fireplace Clearances

what is the vertical clearance for combustible materials (mdf fireplace surround) for a sealed gas only (not wood burning) fireplace? This unit has about 3" of marble and 1" of firebox before the mdf surround. the mdf gets very hot when operated and i think its a fire hazard. is the builder liable even after his one year warranty period has expired? help…
i am an internachi member, though it says otherwise-not yet sure how to fix this

Fireplace clearances are determined by the manufacturer.