Operating within their capabilities, radiant floors can easily meet the heating loads of well-designed, modern structures. Over the last 15 years, however, there have been many projects where designers have exceeded the capability of the radiant floors and have had to face some harsh realities.

The output of a radiant floor is limited in two ways. Firstly, the maximum surface temperature of a radiant floor is limited to around 34.5 degrees Celsius (about 142 watts/m2). Secondly, radiant floors are limited by the amount of energy that can penetrate highly resistant floor coverings, such as certain carpeted and wood floors. Often, these materials limit the actual output to less than 63 watts per square meter.

Radiant ceilings, available from CBS Radiant Heating Systems , are a good alternative. They can easily operate at surface temperatures up to 38 degrees Celsius, delivering in excess of 174 watts per square meter. Since ceilings are typically constructed of gypsum based sheet rock (Gyprok), they offer very little resistance to thermal transfer.

Radiant ceilings accelerate fast, when needed, to meet a big change in heating load. They dissipate energy fast as well. The responsiveness of radiant ceilings makes them excellent for modern controls, placing energy where it is needed when it is needed, and achieving superior comfort and efficiency. Some high mass radiant floors are sluggish in that they take a long time to accelerate to meet the load.

Without a doubt, radiant ceilings cost far less than radiant floors. In most cases they cost less than half that of an under tile radiant floor. Lower cost means more opportunity. They take less effort to design and install. Radiant ceilings are perfect for retrofit situations. It is very inexpensive and easy to lower a ceiling to accommodate the radiant ceiling, but difficult to raise a floor.

Radiant ceilings are not optimal over a polished concrete slab placed on the grade of the earth. In-slab systems are best for these situations. It is also preferable to have radiant floors in rooms with polished terrazzo surface floors, or bathrooms, where occupants are often barefoot. It is a comfortable touch.

But when the going gets tough, the heat losses are high and the floor coverings are plush, radiant ceilings are hard to beat.