What creates comfort in a home? It isn't just the look and functionality of a living space that accounts for its coziness, it's quite literally how it feels, physically, to be there. The key to creating a comfortable environment is making your body feel comfortable, says John Abularrage, owner of the Stone Ridge–based company Advanced Radiant Design, Inc. He has been designing and installing radiant heating systems since 1979.

Radiant floor heating and cooling is an ancient system that has been popular in Europe for the past 50 years, and is making a comeback in the US. As the earliest form of what we know today as central heating, radiant heating was first used 2,000 years ago by the Romans, who warmed their villas and baths via fires placed within stone walls and beneath stone slab floors. With heat routed through flue-like chambers that can still be seen today among Italian ruins, the Romans were able to warm their marble floors. Thus, in wintertime, the Romans were able to enjoy warm bath water as well as walk barefoot on warm stone floors. Meanwhile, during summer, their unheated marble floors served as natural air conditioning.

"From an efficiency standpoint, we can have lower air temperatures with greater comfort and reduce the heat loss of the building," says John Abularrage.

In the early 20th century, radiant heat was rediscovered in the West. But this time, instead of utilizing flue gases, spaces were heated by circulating hot water through metal pipes placed in concrete slabs below the flooring. Following World War II, this heating system became commonplace, usually featuring iron or copper piping installed in concrete slabs, in schools, hospitals, and public buildings. It was also promoted by world-renowned architect Frank Lloyd Wright, whose homes frequently featured stone and masonry floors and walls. In the 1950s, thousands of tract homes Wright designed for Levittown on Long Island and San Francisco were built using steel or copper pipes embedded in slabs.

Radiant heating systems quickly became known for providing consistent comfort and efficiency, as well as for being quiet and significantly reducing dust. Unfortunately, though, many of the first radiant heating systems installed in the US eventually failed due to metal pipes corroding and cracking within the slabs. Compared to its main competitor, forced hot air heating, early radiant heating turned out to be complicated to maintain, so by the 1960s it was all but forgotten in the US.

Radiant heating tubes lock into grooves in the subfloor.

Ironically, though, while Americans turned to cheaper and seemingly more convenient baseboard and forced air heating systems, technical breakthroughs enabled radiant heating to become established as the standard heating system in Europe. This occurred largely thanks to the invention in 1970 of cross-linked polyethylene, or PEX, a highly durable polymer material originally designed as sheathing for underwater cable. Now, says Abularrage, the US is gradually catching up with Europe. That claim is supported by the Radiant Panel Association (RPA), which estimates the industry's average annual growth rate at approximately 20 percent. In 2005 alone, says the RPA, 333 million feet of tubing for radiant heating systems was sold.

The tubes are easily installed between subfloor and flooring.

With a radiant heating system, water is heated and distributed throughout a building's floor structure, thus warming through conduction (the flow of heat from one object to another through direct contact) everything that comes in contact with the flooring—whether bare feet, rugs, or furniture. Although the term "radiant heat" sounds mysterious to the uninitiated, this system—like all modern heating methods—consists of three components, explains Abularrage.

There is an energy source (a water boiler that can be fueled by wood, gas, solar panels, propane, electricity, or oil, or a geothermal heat pump); an energy distribution system (for radiant heating, this means PEX tubing embedded in concrete or circulated beneath or within the subfloor); and a control system, which Abularrage describes as a kind of "cruise control" that monitors temperatures indoors and outdoors and automatically regulates the delivery of heat to keep the indoor environment comfortable in the most efficient way.