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Pipe Insulation in floor over garage

I'm going to be adding a radiator to a room over my garage. Most of the run will be in between floor joists. Does anyone have any suggestions on insulation other than running the pipe, using standard fiberglass pipe wrap and then packing the remaining space with fiberglass batt insulation?



  • acwagner
    acwagner Member Posts: 505
    You can probably skip the pipe insulation and just insulate the joist bay with the pipe directly with batt insulation. Unless the pipe will be really close to the subfloor or the bottom of the joist bay and it will be difficult to insulate with standard batt insulation in those areas.
    Burnham IN5PVNI Boiler, Single Pipe with 290 EDR
    18 Ounce per Square Inch Gauge
    Time Delay Relay in Series with Thermostat
    Operating Pressure 0.3-0.5 Ounce per Square Inch

  • dopey27177
    dopey27177 Member Posts: 887
    Don't be cheap. insulate the pipe with 1" fiberglass pipe insulation and install your bat insulation. Once you close the ceiling and if you made a mistake you will have double work and the itches from fiberglass particles.

  • pecmsg
    pecmsg Member Posts: 4,911
    If you want the floor in that room to be warm......
    Spray Foam the entire area!
  • JakeCK
    JakeCK Member Posts: 1,401
    edited October 2019
    I'm not a fan of spray foam unless it's the only way to deal with water vapor. Its a chemistry experiment in ones house. If the surface temperature is off you get a bad mix, if one of the canisters temps are off you get a bad mix, if the pressure is off in one of the canisters you get a bad mix. If the nozzle even gets partially plugged while spraying you get a bad mix. Pretty much if every environmental parameter isn't perfect you end up with a bad mix and bad mixes often end in stinky noxious foam that doesn't cure. And that stuff is hard/expensive to remove in addition to it being expensive to install. Since there shouldn't be a condensing surface below the finished floor of the room in the floor assembly, vapor and mold shouldn't be a concern. However to elimimate that possibilty, insulate the pipes and create a warm floor install pipe insulation, then fiberglass, cellulose, or rockwool insulation between the bays leaving a couple inch airgap immediately below the subfloor. Then install foam board across the entire garage ceiling against the underside of the joists. Finish with fire rated sheetrock. The fire code sheetrock is critical with it being a garage below. Also make sure all penetrations between the floor assembly are fireblocked.

    Im impartial to cellulose and rockwool because fiberglass is itchy and I believe it will be this century's asbestos once the lawyers get their fingers in it.
  • ScottSecor
    ScottSecor Member Posts: 863
    Are you trying to keep the heat in the pipes -or- are you trying to prevent the cold garage from freezing the pipes? If your trying to keep the heat in the pipes, then by all means I would suggest using at least one inch thick fiberglass pipe insulation.

    If your trying to prevent these pipes from freezing I would suggest not using pipe insulation. Instead, I suggest you use something like fiberglass batts below the heating pipes. The idea is to keep the cold garage air from getting to the heating pipes, especially when the thermostat is satisfied (or you loose power). When the circulator stops the warm air inside the heated room will prevent the pipes from freezing.
  • mroberts5
    mroberts5 Member Posts: 76
    Thanks for the feedback everyone.

    This would be a steam pipe. So I'm not concerned with freezing, but it will be the farthest run from the boiler so I want to make sure I actually get steam there before the thermostat is satisfied by closer radiators (Yes, I will vent the heck out of the run before the radiator).

    I agree that spray would give me the best results, but echo JackCK's concerns. I will likely be going with recommendations similar to his (specifically airbgap between floor and insulation and foam between joists and drywall).