Hydro Tech: The Radiant Future
Why is it when most HVAC engineers think of a radiant system, they relate it only to heating from some type of tubing in a floor? Is this the full picture?
In most heating-only markets, radiant floor heating is desirable for residential construction. Radiant floor heat provides a clean, comfortable, and economical heating alternative. Radiant floor heat systems are invisible, quiet, and healthy. There is no forced air to circulate dust, allergens, or other pollutants. They are energy efficient; people are comfortable at a lower thermostat setting because floors radiate heat directly to occupants, not to the volume above.
Commercial buildings are benefiting from these same heating advantages; areas with large volume, such as warehouses and manufacturing buildings, benefit from reduced losses. Radiant heat systems don’t heat the air in the area above occupants. Buildings with open doors, such as repair garages, airplane hangars, vehicle maintenance shops, car washes, and fire stations, benefit by taking advantage of the concrete floor’s thermal mass. They retain energy during door opening. An additional benefit is that the floor stays dry, as snow and water evaporate quickly.
Radiant heated floors are perfect for agricultural buildings. Kennels, dairies, horse barns, green houses, zoos, and veterinarian clinics benefit from the many advantages of radiant floor heating. Animals and plants appreciate the constant warmth. This is especially important in birthing areas, as newborn animals’ lives depend on maintaining a warm body temperature.
A New Twist On An Old FavoriteWhy stop here? Most buildings constructed in the lower half of the country need heating and cooling. Why not use the benefits of radiant heating and apply the system for cooling? Radiant cooling, to absorb heat and cool the occupants has been tested and works. This concept has been applied in Europe and to a limited level in North America, but issues of control of condensation and available design guides have hindered its acceptance. Several brave engineers, however, are pioneers in improving this technology. Recent presentations at ASHRAE highlighted projects where successful radiant cooling is documented. Research continues that will improve radiant cooling system applications.
HVAC systems usually are designed as all-air systems. Typically, the VAV requirement is between 10% and 20% of conventional HVAC system total air volume. The benefits of radiant cooling systems include reduced ductwork size and fan energy savings.
Installation OptionsRadiant cooling systems have several installation configuration options, with the most common being the ceiling-mounted panel system, usually an aluminum panel with metal tubes connected to the back in which water flows. The challenge has been prevention of condensation in humid environments, although advances in control design are investigating new ideas. One concept is to integrate the passive cooling with an active ventilation air source. This concept, often called chilled beam with DOAS, maintains space dewpoint by controlling the air source (ventilation) at the chilled beam.
Radiant cooling systems can also be applied to concrete floor systems, although the energy storage capacity of concrete floors results in minimal temperature swings. Because a large surface area is available, the slab temperature only needs to be slightly lower than the space; however, research on how carpeting affects radiant cooling is under investigation. And when designed with effective ventilation-only air systems and humidity control, hydronic radiant cooling systems has promise.
A Future With Radiant Heating And CoolingImagine the future: All buildings that benefit now from radiant heating can have cooling as well, from the same system. Commercial buildings, with high ceilings, large south glazing, and stunning architecture, now have a new heating and cooling solution. Imagine a heating and cooling system in the radiant concrete floor, providing all the heating benefits and, during cooling, absorbing all of the radiant heat from the solar gain. Our goal is only to provide comfort to occupants, and they usually walk on the floor, so why not cool them from the floor?
The list of potential applications -churches, auditoriums, concert halls, and convention centers - is promising. Cooling from a radiant floor - that is the future of radiant! ES