• In this video, This Old House plumbing and heating contractor Richard Trethewey explains how to install radiant heat.


    1. Screw aluminum transfer plates to underside of subfloor; install two plates per joist bay.
    2. Assemble radiant-heat manifold with circulating pump, sensor, relay switch and mixing valve.
    3. Connect supply and return hot-water pipes from boiler to radiant-floor mixing station.
    4. Drill 7/8-inch-diameter holes through floor joists for radiant-heat tubing.
    5. Run tubing through holes in joists and along aluminum transfer plates.
    6. Use rubber mallet to tap tubing into slots in transfer plates.
    7. Once all the tubing is installed, insulate between the joists with fiberglass batts.
    8. Connect ends of radiant-heat tubing to manifold at mixing station.
    9. Have a licensed electrician run wire from room thermostat to relay switch and then to circulating pump.
    • 6 to 8 hours, depending on size of the room and complexity of the heating system
    • Difficulty: Hard
      Professional installation recommended

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      Tools List

      • drill
      • hammer drill
        End nippers,
        used to cut nails protruding from subfloor
      • mallet
        Right-angle drill,
        used to drill holes through floor joists
      • Rubber mallet,
        used to tap radiant-heat tubing into the transfer plates

      Shopping List

      1. Radiant-heat tubing

      2. Aluminum transfer plate

      3. Self-tapping screws
      for attaching the transfer plates 4. Manifold, including sensor
      mixing valve, relay switch and circulating pump

      5. Fiberglass insulation
      used to insulate between floor joists 6. Room thermostat