Gas furnace sitting on rigid foam insulation

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.

Morning, Andrew.
Hope this post finds you well.

Welcome back to the forum. Been some time.

Could you please post the manufacturer, model and serial number?
As well, an image further back.
Looking forward to your reply.

Google the installation instructions for the furnace and you will have your answer.

And, welcome back to our forum, Andrew!..Enjoy! :smile:


He already did. Read his post again.

Why? How will that answer his question?

Wood (which should fully cover over) should be placed between the furnace and the RFI.

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Ah, thanks.

Well he has a defect that needs correction, then. :upside_down_face:

Grand daughter asked me something at the same time I was reading…my bad.


Andrew, on a final walkthrough by a building inspector, they will look for what was signed off on already on the permit and what hasn’t. They will then focus on what hasn’t been signed off on. In your picture maybe the inspector caught it during the HVAC inspection and verbally told the installer to fix it and signed off on it anyway when the contractor verbally agreed. See what I am getting at? Nothing written about it on the permit notes…

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Man, has that happened so many times that the take and pass notes along now…the AHJs, around here.