Radiant Heating & Cooling: An Overview


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Radiant heating & Cooling: An overview

By Dale Yelnich

Radiant heating, and the reverse process called radiant cooling, is one of the most efficient ways to both heat and cool your house or home. Simply put, a radiantly heated and/or cooled space is warmed or cooled by heat transferred through the floor, the walls, the ceiling, either alone or in combination. The process is described as thermal or infrared radiation, and works like this. Any heat source, or cooling source, can be felt some distance away. For example, the flame from a match can be felt before touching it, exactly the same as the chill from an ice cube. Using these properties, radiant heating and cooling can be harnessed to either heat or cool a living space, yet be highly cost effective.

This type of developed system has been around for centuries, with some of the first forms of radiant heating done by drafting smoke from fires, through dug-out trenches, beneath the floor. In about 1000 BC, Romans began using underfloor heating, called hypocaust, which were essentially furnacesplaced beneath raised tiled flooring. This design of heating was employed extensively in Roman spas and baths. The first time a modern variety of wet radiant heating occurred was when the Russians, in the early 18th century, began piping hot water under the floor of the summer palace used by Peter the Great. It is not a new invention, but modern forms, using modern materials, make it far less maintenance intensive and much more efficient.

In todays applications, there are essentially three different types being installed and used. They are hydronic or wet heating and cooling systems, air or dry radiant heating systems, and electrically powered heating types. Any of these are capable of being mounted in floors, walls or ceilings, with the most practical and the more common floor mounted systems now in vogue. Wet designs are the only kind that offer viable radiant cooling, and they lead the way in efficiency, followed by electrical radiant heating systems, with the least efficient types being the dry variety. For practical purposes within this article, let’s begin with the two forms of purely radiant heating.

Dry systems come in third on the efficiency table, but they are, overall, the most versatile of the radiant heating types. Dry systems funnel air between spaces in floors, walls and ceilings, and essentially work the same way as a wet system, except for one exception. All dry systems must first use air to heat the channels that they travel through before they can give off any temperature effect into the room that is being served. It takes more time, and more energy, to do this, and although its versatility means that virtually any house can be retrofitted with air channels between floor joists or ceiling panels, dry systems are used mainly for commercial applications, and it is rarely installed into residences. In almost all residential applications, it is easier to install a forced air furnace with ductwork and vents than it is to install dry radiant heating.

Electrical radiant heating can be cost effective to use, especially when coupled to solar power or when programmed to come on in off-peak hours. The largest advantage of this type is that it provides shorter heating times in every room it serves. Although generally installed between the sub-floor and the floor, companies do exist that will retrofit regular flooring to electrical radiant heating by installing the heating cables between the joist bays beneath the floor. Even though it is a clean and environmentally friendly way to provide heat, electricity is the most expensive way to do it, so unless you have a solar set-up or a very small space to keep warm, radiant heating done electrically is not a cost effective option.

Which brings us to hydronic radiant heating and cooling. In the majority of cases, hydronic heating pipes are mounted inside of concrete slabs during new construction. The pipes are made of a plasticized material called PEX, which is virtually maintenance free and will last the life of the concrete it is embedded within. However, retrofitting is possible using radiant heating panels that can be mounted to walls or ceilings. Most residential panels are made specifically for heating, but there are some manufactured for dual purpose applications, as they can supply hot water for heating or chilled water for cooling.

The soul of a hydronic system is the boiler. This is where the water is heated or cooled and then sent into the PEX piping or the radiant panels. Boilers are generally heated by natural gas, coolers are powered with electricity, and the overall savings by using this system is around 20%, or more, compared to a forced air system. Add-on panels will be slightly less efficient. Be aware that radiant cooling systems typically have condensation problems in places with high humidity. Condensation can lead to damp flooring or ceilings, and over time, this moisture will increase the chances of mold or mildew infestation. Ideally, these systems are best used in arid climates where humidity in the air is not a factor. In general, the more humidity there is in the air, the greater the chance for condensation that can occur in your home.

Radiant heating and cooling has come a long way from the ancient Roman’s, even though the principle remains the same. But with modern materials like PEX, boilers that are rated at over 90% efficiency, and with the versatility to retrofit homes, this is one of the best, most comfortable and cost effective ways to keep your home heated during the winter, and cooled during the summer.

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