the plate on the back of the heater. stove wall1jpg. 2014 12 20_02 . our house was originally designed for a gas fireplace: there is a chimney box framed in that was then hidden behind drywall no gas line ever arrived at the . hearth pad and heat shields. this way i was able to accommodate the extension of the vapor barrier behind the cedar and in front of the cement board . isokern fireplace wfirebrick.