What types of material, other than drywall, are acceptable by Ohio HVAC Code for the ceiling of a small furnace room which will:

  1. Have return air ducts (only) passing through it to attic space.
  2. Butt up against a brick chimney on one edge (B-Vent installed in the flue)
  • What materials are you considering? Fiber drop ceiling? Brick? Concrete? Wood paneling?
    – wallyk
    Aug 21, 2013 at 17:00
  • 1
    No idea about your local code, but cement-board (tile backer - 3x5x1/2" sheets) is a pretty decent material. Then again, two layers of 5/8 type X drywall with the joints in both layers mudded is a standard fire-rated covering...
    – Ecnerwal
    Nov 20, 2013 at 4:21
  • This probably depends in part on the furnace. My high-efficiency condensing furnace (installed a few years ago) is certified to be installed right against flammables (or have flammables installed right against it). ... If you need state codes, I'd suggest asking your town's inspector rather than a global website.
    – keshlam
    Jul 18, 2014 at 1:48

3 Answers 3


Definitely don't use WOOD as suggested by DMoore! Yes, consult your local Ohio codes.

A new material, probably not rated or considered in Ohio code, but used extensively outside the US, is MGO board, which is fireproof, waterproof, mold proof... I wish this would get certified, as it's a much better idea than drywall in the first place! This is NOT Chinese drywall, which is just poor quality unregulated imported garbage. A reputable MGO board company will probably have certifications soon for this type of installation.

At least be glad that the old asbestos board, which was used extensively decades ago, is gone, after the medical concerns surrounding that material arose.


Paint it black, use left over wood flooring, plywood is fine too.


Any material you use will need to be fireproof, since it contacts the brick chimney. You can't count on the existing furnace to be the last one ever installed in that location, so any installation you do now will have to be safe for the next furnace, too... and since you can't know anything about the next furnace's specifcations, you need to take every reasonable precaution now. Failing that, you potentially assume liability for a house fire later down the line.

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