I just have a folded regular old bath towel under mine. you probably don't need anything if you are doing minimal ironing or have enough time between irons to allow things to cool. however, if I have done a lot of chain piecing and subsequently have a lot of ironing to do, I will iron in different corners of the mat (for example, in a clockwise fashion), again, to allow one area to cool a bit. Constant or sustained pressing in one area is what I avoid. is it necessary? I have no idea, but that's what I do.