Continuing the discussion from Styrofoam Supports at Furnace:
I have seen 3 furnaces in the past month, installed in the past year, resting on 2" rigid foam insulation pads. Manufacturers installation instructions specify that the only acceptable combustible material below the furnace is wood. I understand that foam provides R value from the cold concrete, and dampens vibration. I do not understand how it passes the building inspectors final walk through.