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Will radiant heat affect drywall (i.e. make it brittle and crack)?

I live in a building that was built around 1950, the ceilings are plaster, and there is radiant heat in the ceiling, above the plaster. My apartment’s plaster ceiling is in horrible shape so I'd like to remove it and replace it with drywall.

I spoke with someone at USG (the drywall manufacturer) who said that drywall can withstand temperatures up to 125 degrees F. When drywall is exposed to higher temperatures, it can get very brittle and ultimately crack.

I'm wondering whether that could happen if I use drywall for the ceiling. The drywall would only be about an inch below the radiant heat fins. I’m not quite sure how hot the radiant heat gets in the middle of winter….but it's probably pretty hot given that the heat can be felt in the floor above (which is through a metal deck and concrete and about 16” above the radiant heat).

Also, when the temperature is below zero outside, the water leaves the boiler at around 200 degrees F. The temperature drops as it goes through the system, but I don't know by how many degrees. It's a high-rise, so the water definitely covers a lot of distance.

If you have any thoughts or insight, thank you in advance! Of course, replacing the plaster with drywall would require building approval, etc. but that's not the issue at the moment. Right now, I'm just curious if it's okay to install drywall so close to radiant heat.

Here's a photo of what the radiant heat looks like in the ceiling.


  • Mark Eatherton
    Mark Eatherton Member Posts: 5,837
    In my 40 years of rolling around, I don't think I've ever seen radiant ceiling quite like that. It actually looks like a finned tube convector to me.

    As for temps, I've run 160 F water through my drywalled, truly radiant (Rehau) ceiling, and have not seen any issues in the 6 or 7 years its been installed. I think most manufacturers are covering their collective butts by dictating such a low temperature, knowing that people are going to exceed it anyway.

    Are you in Chicago per chance? I keep getting complaint calls from an older radiant project in Chicago. I think I've determined it is a radiant floor system with no insulation to control directional flow of energy... It ACTS like a radiant ceiling when the occupant above keeps their thermostat turned way too high, because they can...

    It's not so much a case of "You got what you paid for", as it is a matter of "You DIDN'T get what you DIDN'T pay for, and you're NOT going to get what you thought you were in the way of comfort". Borrowed from Heatboy.