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Radiant Heat

A visit to any plumbing and heating trade show will give evidence to the rise in popularity of radiant heat. Not only can it warm the home, it can melt ice off the sidewalk or driveway, or warm seedbeds in a greenhouse. Many factors contribute to its application and promotion. This series of articles will deal with hot water radiant.

Comfort is the prime factor. The human body uses the feet and head to dispose of excess heat. Because of this, warming the floor is not only physically pleasing, but the room will feel warmer than it actually is, allowing for lower temperature settings and fuel conservation. The downside to radiant for fuel conservation is slow recovery. With lower water temperatures in the tubing, setting the thermostat back at night or when the house is vacant for short periods is not possible, unless one wants to live with the discomfort while the temperature slowly rises. An alternative to this will be offered under the heading of "combination radiant and ducted".

Radiant heat can be installed in the ceiling when no alternatives are available, but the comfort factor and efficiency are compromised.

Aesthetics plays an important part in the installation. Baseboard radiators around the perimeter of each room or free standing cast iron units are eliminated. with the piping in the floor or ceiling, the decor is not affected.

With hot water as the median for radiant heat, domestic hot water can be produced by the boiler or water heater, allowing one appliance to do double duty.

The advent of computerized boiler controls that sense indoor and outdoor temperatures and adjust the operating temperature of the boiler to meet demand instead of maintaining a constant high temperature setting increases the overall efficiency of the system. During warm weather, the boiler maintains just enough temperature to satisfy domestic needs.

Radiant tubing comes in a variety of materials. Cpvc, polyethylene, pex (cross linked polyethylene; and many types of pex as well) reinforced rubber, Polybutylene, and the original one, copper.

Pex-al-pex and poly-al-poly describe tubing that is layered. A core of pex or polyethylene is wrapped with aluminum then an outer layer of pex or polyethylene covers the aluminum. The aluminum forms an oxygen barrier to prevent deterioration of the plastic, and helps retain the shape of the tubing during installation. When bent into a curve to make return loops, the aluminum stops the plastic from springing back.

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