I have my wood stove on a raised cement pad. However I need 18 inches of noncombustible protection in front of the stove. There is carpet there now and I don't want to cut it....is there a cheaper type of noncombustible mat that I can use....its to just catch sparks right?....I could be way off on that though...I guess my question, is does it have to meet a specific R value if its just in front or not....what have you folks used?