Watch this video from This Old House to learn 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.