# Gas furnace sitting on rigid foam insulation **URL:** \ **Category:** Inspecting HVAC Systems\ **Created:** [April 10, 2021, 4:53am UTC](https://forum.nachi.org/t/gas-furnace-sitting-on-rigid-foam-insulation/196460 "2021-04-10T04:53:28Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![adanylchuk](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/adanylchuk/32/180292_2.png) [@adanylchuk](https://forum.nachi.org/u/adanylchuk)\ **Post date:** [April 10, 2021, 4:53am UTC](https://forum.nachi.org/t/gas-furnace-sitting-on-rigid-foam-insulation/196460/1 "2021-04-10T04:53:29Z")
Continuing the discussion from [Styrofoam Supports at Furnace](https://forum.nachi.org/t/styrofoam-supports-at-furnace/942/7): 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. ![IMG_4036](https://global.discourse-cdn.com/internachi/original/3X/a/b/ab520ce32e2ed1687a5b839d27eb7ea167c00ff9.jpeg) ---
**Author:** ![ryoung7](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/ryoung7/32/188798_2.png) [@ryoung7](https://forum.nachi.org/u/ryoung7)\ **Post date:** [April 10, 2021, 9:56am UTC](https://forum.nachi.org/t/gas-furnace-sitting-on-rigid-foam-insulation/196460/2 "2021-04-10T09:56:18Z")
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. Regards. Robert ---
**Author:** ![lkage](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/lkage/32/347658_2.png) [@lkage](https://forum.nachi.org/u/lkage)\ **Post date:** [April 10, 2021, 11:49am UTC](https://forum.nachi.org/t/gas-furnace-sitting-on-rigid-foam-insulation/196460/3 "2021-04-10T11:49:10Z")
Google the installation instructions for the furnace and you will have your answer. And, welcome back to our forum, Andrew!..Enjoy! 😄 ---
**Author:** ![jjonas](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/jjonas/32/301755_2.png) [@jjonas](https://forum.nachi.org/u/jjonas)\ **Post date:** [April 10, 2021, 12:53pm UTC](https://forum.nachi.org/t/gas-furnace-sitting-on-rigid-foam-insulation/196460/4 "2021-04-10T12:53:43Z")
> [@lkage](#): > > Google the installation instructions for the furnace and you will have your answer. He already did. Read his post again. ---
**Author:** ![jjonas](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/jjonas/32/301755_2.png) [@jjonas](https://forum.nachi.org/u/jjonas)\ **Post date:** [April 10, 2021, 12:54pm UTC](https://forum.nachi.org/t/gas-furnace-sitting-on-rigid-foam-insulation/196460/5 "2021-04-10T12:54:45Z")
> [@ryoung7](#): > > Could you please post the manufacturer, model and serial number? > As well, an image further back. Why? How will that answer his question? ---
**Author:** ![jjonas](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/jjonas/32/301755_2.png) [@jjonas](https://forum.nachi.org/u/jjonas)\ **Post date:** [April 10, 2021, 12:56pm UTC](https://forum.nachi.org/t/gas-furnace-sitting-on-rigid-foam-insulation/196460/6 "2021-04-10T12:56:15Z")
> [@adanylchuk](#): > > Manufacturers installation instructions specify that the only acceptable combustible material below the furnace is wood. Wood (which should fully cover over) should be placed between the furnace and the RFI. ---
**Author:** ![lkage](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/lkage/32/347658_2.png) [@lkage](https://forum.nachi.org/u/lkage)\ **Post date:** [April 10, 2021, 1:02pm UTC](https://forum.nachi.org/t/gas-furnace-sitting-on-rigid-foam-insulation/196460/7 "2021-04-10T13:02:16Z")
> [@jjonas](#): > > He already did. Read his post again. Ah, thanks. Well he has a defect that needs correction, then. 🙃 Grand daughter asked me something at the same time I was reading…my bad. ---
**Author:** ![mdurante](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/mdurante/32/289617_2.png) [@mdurante](https://forum.nachi.org/u/mdurante)\ **Post date:** [April 10, 2021, 1:50pm UTC](https://forum.nachi.org/t/gas-furnace-sitting-on-rigid-foam-insulation/196460/8 "2021-04-10T13:50:03Z")
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… ---
**Author:** ![lkage](https://sea2.discourse-cdn.com/internachi/user_avatar/forum.nachi.org/lkage/32/347658_2.png) [@lkage](https://forum.nachi.org/u/lkage)\ **Post date:** [April 10, 2021, 4:31pm UTC](https://forum.nachi.org/t/gas-furnace-sitting-on-rigid-foam-insulation/196460/9 "2021-04-10T16:31:52Z")
> [@mdurante](#): > > 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… Man, has that happened so many times that the take and pass notes along now…the AHJs, around here.