Richard screws aluminum track into the joist bay
Photo: Russell Kaye
Richard Trethewey screws an aluminum track into a joist bay at the TOH TV project house. The tracks will pull heat from warm water in the radiant tubing to warm the dining room floor above.
Loops of white plastic tubing hang suspended like hula hoops in the basement of Madeline Krauss and Paul Friedberg's Shingle-style home, the site of This Old House TV's Newton project. Richard Trethewey, TOH's plumbing and heating expert, pulls another length of tubing from a decoiler on the basement floor and feeds it to heating contractor John Perry, who snakes it along a joist bay over his head. Richard steps onto a ladder and gently taps the thin white hose into the grooves of aluminum tracks screwed between the joists. "We're turning the entire first floor of this house into a giant radiator," he says. "You'll never feel cold when we're through, and you won't need slippers, either."

Richard is working with Perry to bring hydronic radiant heat to this 111-year-old house. If you've ever warmed yourself in front of an open fire, you've experienced radiant heat. Unlike rising hot air, radiant heat travels in all directions, warming cooler objects around it. Delivered via warm water in plastic tubing installed in a floor, radiant moves out from there, making the room feel warm and comfortable.

Though installing a radiant system can run up to 50 percent more than, for example, conventional forced-air heat, it saves 30 percent in energy costs, eventually paying for itself. Putting it into new construction is easy: Special wood plates screwed to the joists double as subflooring. But retrofitting the tubing under an existing floor presents challenges. If a room is gutted down to the joists, it's easy enough to lay down the wood plates. But that's not possible when flooring stays put.

Here's a look at the three most popular places for retrofitting radiant and what the pros do in each case to bring cozy warmth to older houses.

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