Styrofoam Supports at Furnace

I see a lot of attic installed furnaces in this area with styrofoam blocks acting as supports for the side mounted unit. It doesn’t seem right to me for a gas furnace to be supported by styrofoam. It is very common, in fact the supply houses stock the styrofoam for this purpose. I have written e-mails to Carrier and Trane about this and have been routed to local distributors, but so far, no answers. Any thoughts?

depending on the ratio of styrene to what ever else make polystyrene, or styrafoam, it can be soft like a disposible cup, grainy like computer corner packing pieses or even quite strong and realy realy shock absorbant, like what fills aircraft panels and some wing/tail sections.

Rather than questioning whether styrofoam will support the weight of a furnace, I’m more concerned with heat or fire! Styrofoam is a combustible.

Styrofaom supports are used regularly for furnace supports…**but they are encased in a plastic substance. **They look like little wheels.

If you are seeing fully exposed styrofoam, I would simply recommend replacing styrofoam supports with a better material. Rubber is the best material which will absorb the rapid movement of the blower motor. No vibration.

I have been writing this installation method up for the last year or so and even posted here on the board a year or so ago to see if anyone else had any thoughts on this. As I was searching for my old post I found this one instead so it will do.

I now have in my possession a letter from the Mgr, Product Applications & Inside Service at Lennox Industries that approves of this method of installing their furnaces.

Now, there are a couple of caveats that must be followed:

  1. The styrofoam must be of sufficient size (3" x 4" min cross section) to support the weight of the equipment.
  2. The styrofoam support pads must be positioned so that they do not contact any gas, electrical or condensate connections (diagram in letter)
  3. Must maintain >6" clearance to vent pipe.
  4. Compression of styrofoam support pads must ensure unit maintains level orientation after installation of all components, i.e. evaporator coil, etc.
  5. All other installation requirements in the instructions along with all local and national codes must be met.
  6. If another styrofoam material other than Modified Expanded Polystyrene (EPS) produced by Houston Foam Plastics is used then it too must meet or exceed EPS specifications. An EPS MSDS sheet was included for reference.

So, looks like at least Lennox has gone on record as approving this installation method. I will likely not write this up any longer for any mfg.

I have not observed that type of material used up here and I hope that We don’t start using it. My professional opinion is that it will not stand the test of time. Styrofoam does compress some over time and if the gas supply was hard piped into the gas valve could create stress on the gas valve. I personally would not write it up either but does not mean that I agree with the installation.

Shouldn’t it be on non-combustible supports?