Repair & Maintenance

What is radiant heat?

By Eleanor Stern
Info Guru,

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radiant heat
What is Radiant Heat? Our information experts explain everything you'll ever need to know about Radiant Heating.
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Radiant heat sounds like the title for an action thriller starring Jean Claude Van Damme or a novel you can find in the Romance section of Barnes and Noble. However, radiant heat is actually heat transferred from one body to another which is not in contact. It is exuded from hot surfaces and directly warms people and objects in the room rather than warming the air. Ok, that's great, I'm not a scientist, what is radiant heat?

Examples of Radiant Heat

There are examples of radiant heat all around us: the sun heating a roof, a bonfire, or a radiator heating up a room, (hence the term radiant heat.) When the sun shines down on the roof it warms the roof without coming into actual physical contact with the roof. When the radiator is turned on, it warms the entire room. But for the homebuilder or home owner, the term radiant heat is shorthand for a radiant heating system. A series of pipes connected to a water heater and a pump which delivers hot water, and therefore heat to all parts of a structure.

Although relatively new to American builders and consumers, nearly 70% of all heating systems installed today in Europe are radiant heating type systems.

Radiant Heat's history

Radiant heat technology has existed since Roman times. Romans invented the Hypocaust system, which is a form of central heating. Hypocaust means "heat from below", and it comes from the Greek words hypo and kaiein. Hypo means below or underneath and Kaiein means to burn or light a fire. Sergius Orata is thought to be the inventor of the Hypocaust system which was originally designed for bathhouses and private houses.

Radiant heat's introduction in the U.S. and Europe

The history of modern heating techniques began in the 1950's and 60's. Unfortunately, the first American installations were plagued with problems. Early installations used copper, which would react with the cement in the floors and corrode. Then the copper expanded and contracted in the cement. The cement cracked and copper broke within the cracks.

The switch to PEX piping

In the 80's American designers began to copy European radiant heat methods and began using PEX piping instead of copper piping. PEX stands for Cross Linked Polythylene. Cross-linked polyethylene (PEX) is a high-temperature, flexible plastic (polymer) pipe. The cross-linking raises the thermal stability of the material under load. Thus, the resistance to environmental stress cracking, creep, and slow crack growth were greatly improved over copper or standard polyethylene.

The advantages of PEX systems

Even builders and plumbers accustomed to working with traditional piping materials are finding it easy to transition to PEX piping. Some additional training may be needed for installers to learn the layout, pipe support spacing, and connection methods with the new system.

Specialized tools widely available to cut the tubing, install connections, and check the tightness of crimped connections. Designers can layout PEX in a traditional tree and branch arrangement. Most are extremely satisfied with the results, as it doesn't corrode or develop pinhole leaks, is chlorine resistant, scale resistant and has fewer fittings, connections and elbows. PEX doesn't react or deteriorate like copper. These new systems can last over 200 years.

Troubleshooting the installation process

Fred Seton of Radiant owns a radiant heating company and offers some advice. He very eloquently explains the major problems of using radiant heating systems and what he has done to combat these issues

Fred says, "There is a very large gap between the theoretical information furnished by the manufacturers of heating equipment and the information needed by the person actually installing the system." To make installation more user friendly an installer can offer a fee based design service for radiant projects, complete instructions, material list, assembly diagrams, tubing layout, material specification and troubleshooting. Some common Questions and Answers

Fred Seton answers key questions about radiant heating systems regarding efficiency and cost.

Is a radiant heating system always more efficient? No. Sometimes fuel is more efficient. If your house is small to medium sized, well insulated, or uses advanced construction methods, you may not need to use a radiant system. What does radiant heating cost? A well designed radiant system with a 96% efficient condensing boiler, stainless steel indirect water heater, Pex tubing, brass manifolds, thermostats and all necessary equipment to install it will normally cost less than $3.00 per Sq. Ft., or less than $2.00 for a slab on grade. The larger the home, the smaller the cost of equipment per Sq. Ft. A 5,000 Sq. Ft home will cost less than $2.00 per Sq. Ft. even using the very best equipment.

As fuel costs continue to increase, and population centers expsnd into regions with more extreme winters, the growth of radiant heating sytems is expected to grow as well. Experts expect that within a few years, no one will need to ask 'What is Radiant Heat,' - homes and businesses using this efficient heating method will be as common as those now using forced hot air or traditional radiators to fend off winter's chill.

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