I am in the middle of building a gun safe. I would like some type of fire protection. I am thinking fire rated sheetrock and fiberglass isulation. what would you suggest the thickness (how many sheets) of sheetrock should I line the interior with. Keeping in mind that the safe will be located in my Basement. I would like to be able to keep the inside temp. of the safe down to a level that would protect my guns. I do not care about the safe at all. Would a thickness of 3 inches be sufficient?