Manufacturers and installers of radiant-floor heating systems highlight improved comfort, since infrared radiant waves can warm a person directly without the drafts and dust associated with furnaces and heat pumps.

Trouble is, most folks are less comfortable with a radiant floor system’s perceived expense. However, continued technological advances are making this heating choice a lot more comfortable for more homeowners.

For one family building their Landisville, Pa., dream home in the state’s south-central Susquehanna Valley region, recent radiant-heating developments made this choice very real and practical.

Fuel flexibility

“A big benefit is that the system doesn’t depend on electricity,” says Joe Giandalia, owner of Comfortable Design Heating and Cooling, Wrightsville, Pa.

“A boiler is used to heat hot water that circulates through the floor piping. This gives the homeowner fuel flexibility.”

Because natural gas was not available on the lot, Giandalia installed a boiler using an oil burner and No. 2 fuel oil. Another boiler feature solved air venting issues associated with combustion appliances.

“In many homes with oil boilers, air is drawn from the living space to fire the boiler,” says Giandalia. “So that air is being drawn into the house and into the basement where the boiler is usually located.

“Although an oil boiler doesn’t draw nearly as much air as a gas boiler, there’s still an infiltration and exhaust issue. There’s a concern with cold air drafting downstairs and exhaust that needs a chimney. But the Burnham boiler used here avoids both problems.”

Giandalia installed a Burnham LE direct-vent boiler. This design uses through-the-wall vent piping to eliminate the need for a chimney.

Intake air is drawn through the same double-wall, Z-flex, stainless steel vent piping, so a single vent pipe does it all. Plus, the boiler itself is compact, measuring less than 3 ft high.

“It’s made of cast iron,” says Giandalia. “But it contains just over five gallons of water, which means the size is smaller and the heating response is faster than larger, traditional cast iron boilers.”

Brisk acceleration

Rapid heating response is key to the system’s success. The low-water, low-mass boiler can accelerate from room temperature to 140°F in less than 90 sec.

Operating only on demand from a cold start saves fuel. The warm boiler water is then fed to the system piping through a 1-in. supply header.

A primary loop maintains sufficient temperature inside the boiler to prevent water from condensing on the boiler’s internal heat exchanger. A secondary loop, fed by a variable-speed injection pump, supplies hot water to the system.

Giandalia installed a microprocessor control to operate the injection pump. Sensors were situated on the lines that feed six interior zones.

A sensor was also installed outside. The control calculates the amount of hot water required, turns on the boiler, and injects only the hot water needed for that particular zone.

Radiant piping installation details

The zone for the basement and garage uses 1/2-in. PEXc flexible radiant piping. Before the concrete was poured, the piping was tied to a wire mesh. Four inches of concrete were poured, then wire mesh was hooked up into the liquid concrete.

The concrete was troweled and cured normally. As a result, the homeowner enjoys a heated garage, part of which is used for woodworking.

Two zones are on the first floor, one for the kitchen/dining area and another for the living/family room area. Here, the 1/2-in. piping was laid into grooves created by sleepers nailed to the subfloor.

Next, lightweight Gypcrete concrete was poured over the floor to a 2-in. level above the piping, a technique that was also used for the second-floor master and secondary bathrooms.

This technique is suitable for tile, carpet, and resilient flooring, which allows the entire floor to act as a giant emitter of radiant heat waves without the need for radiators or forced air.

A typical surface temperature for a tiled slab floor can be as low as 85° created by 115° supply fluid, with higher supply water temperatures required by carpeted floors.

Baseboard radiation was used to heat three zones on the second floor, because the heating requirements are less critical.

Automation calculation

Each zone has its own room temperature unit (RTU) that operates as a temperature sensor and allows temperature selection.

When the room needs heat, the RTU triggers the zone circulator and boiler. It automatically calculates the lowest temperature water required based on previous cycles, plus current outdoor and indoor air temperatures.

A night-setback feature automatically dials down the temperature. Before the occupants wake up, the living space is returned to normal temperature. This capability not only saves energy, it makes the tiled bathroom floor more comfortable for the toes.

The second-floor master bath includes a Jacuzzi, which is supplied by a 40-gal, indirect water heater that handles all domestic water needs. The indirect water heater works well with the low-mass boiler.

Functioning as a storage tank with a corrosion-free, polyethylene inner tank, the indirect water heater uses an internal heat exchanger that uses a small amount of hot boiler water to maintain temperature. As a result, it can replenish hot water at a faster rate than an electric water heater, without the maintenance problems.

“This hot water system shifts smoothly to deliver the right amount of heat to the zone and indirect water heater as needed,” says Giandalia. “With these developments, the popularity of radiant heat will keep accelerating.”

For more information on Burnham boilers and radiant products, contact the company at 717-397-4701; 717-293-5827 (fax); (Web site).