Most insulation is fire-rated, but mineral wool is among the best. Also known as rock wool or slag wool, this material is one of the oldest types of insulation composed of noncombustible fibers and can withstand heat in excess of 1,800 degrees F. Unlike fiberglass insulation, mineral wool does not melt when exposed to such high heat. NSi's
semirigid strips make for easy DIY installation. $99 per 35-pound bag. 800-321-5847.