Published on Thu, Sep 14, 2006
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Home Improvement

Radiant heat warms from inside out, conserves energy

By Jack Kintner

This is the second of a four part series on Home Improvement.

Unless you live alone, chances are there’s a battle over the thermostat in your house once the weather turns chilly. Contractor Frank Kaligas helped Donald and Diane Lahti find a solution to this by installing a radiant heating package in their new 3,800-square foot house in Birch Bay.

“It’s more expensive to install, but saves a lot of money in the long run and never needs to be touched once you’ve got it set,” Kaligas said recently while putting the finishing touches on the Lahti’s house.

The address is 4790 Highland Drive, and since it sits on the hill behind Birch Bay State Park it commands a view of most of the bay from a two-story deck on the waterside of the house.

The upper deck is an extension of the house’s main floor that’s at ground level on the street side, and the lower level is concrete molded to look like slate tiles.

The innovative thing is that along with the main floor and concrete slab basement, the lower outside deck is also heated with hot water radiant heat.

“You can shut it off, of course, but it loses surprisingly little circulating outside,” said Kaligas, “because it’s constantly circulating and because it’s heating a concrete slab that has a lot of thermal mass,” meaning that even outdoors, once it’s warmed up it tends to stay that way.

That’s the advantage of hot water radiant heat. The homeowner buys electricity to heat the boiler that heats the water that heats the house. The energy never has to go through the highly inefficient step of becoming a mass of hot air in order to heat the structure. Hot air’s expensive to produce and dissipates quickly once it’s out of the furnace and into the room.

That’s also the disadvantage, for some people. No forced (circulating) air means no air conditioning, which may sound like a frill in this part of the country until you look at the number of heat pumps that homeowners are choosing to install.

“The house will have ceiling fans,” said Kaligas, “but by applying heat directly to the structure and insulating the parts of it that come in close contact with the ground, a very steady and even heat can be maintained.”

The insulation in the Lahti’s basement is so high it’s difficult to measure. The slab is insulated from below with rigid foam bats and is permeated by the flexible PEX cross-linked polyethylene tubing that was first produced in Europe. It’s finished as a flat (non-molded) surface and then was given an acid wash to darken the color to a rich honey-brown.

The walls are made up of concrete-filled polystyrene “bricks” that provide something approaching R80 in insulation value. Once that concrete slab is heated there’s nowhere for the heat to go but up into the rest of the house through the structure.

“People usually end up setting these things somewhere between 65 and 68 degrees,” Kaligas said, “which seems cold if you’re used to forced air heat, but it’s a measure of how much more efficient this is.” For one, no heat is lost due to pressure differences between inside and outside.

Forced air by its design pressurizes the inside of a house, sending heated air out through windows and doors even when they’re closed, unless they’re well-sealed and never opened. With radiant heat, the inside of the structure itself is warmed, letting the outside air remain cold while keeping the air inside toasty. Savings over time are estimated to be about 30 percent, according to industry publications.