I am getting ready to install my first wood stove, a US Stove for 2000 square feet. I am in the process of building a hearth pad. I already have a 2x4 frame built on the floor that meets the required distances from the wall. Now I am moving onto the surface, I am wanting to have a tile hearth pad and want to make sure to meet the required r-value of 1.4. I would have to buy two 4-packs of Micore 300 to have enough material to lay down two layers to get the required r-value. This route would cost about $330 dollars as each pack is $166. I would then put a layer of hardibacker, then tile. It would get me to a r-value of around 2.25. My question is: has anyone ever laid down the imperial stove board you can buy at lowes or TSC, then laid down the hardibacker and tile on top of it? The stove board by itself has an r-value of1.5 which is enough for my stove, especially after putting down the hardibacker and tile. This would save me about $170, and the stove boards are more eaily accessible. Thanks.