One technology often overlooked as an energy efficient solution to heating/cooling large spaces is radiant. Louise Harris looks at the energy saving potential of ceiling-mounted radiant heating and cooling systems.
When designing a heating system for a large space, it is predominantly the choice of heat transfer system which offers the greatest potential for saving energy. The heat must be delivered as quickly and evenly as possible, but the system must also be able to react quickly to changes in the load of heating and cooling required in order to maximise the benefit that is gained from it. In simple terms, the heat transfer system needs to ensure that the heat is used in the right place at the right time.
Within this framework there are four key areas which affect the energy efficiency of a heat transfer system:
• Human temperature perception - This is the arithmetic mean of the indoor air temperature and the surface temperature, e.g. of the walls, ceiling and floor. By increasing the radiant component of a heating system, it is possible to achieve a comfortable environment with a lower air temperature.
• Heat distribution up to ceiling height Some heating systems result in higher temperatures at ceiling level than at ground level. This reduces efficiency.
• Reaction time and controllability - As buildings become better insulated, they need less energy so even small variations in heat load can result in major temperature fluctuations. Systems that can react quickly to change and bring the temperature to the desired level to conserve energy and reduce costs.
• System temperature - Low flow temperatures are important in system efficiency. A heat transfer system with a flow temperature of 50 deg C will use around 90 per cent more energy than a system that runs at a flow temperature of 30 deg C.
Based on the natural principle of thermal radiation, as used by the sun, radiant heating and cooling panels transmit radiant energy in the form of electromagnetic rays. Installed as heating or cooling ceilings these rays warm or cool the objects and people within a space, rather than the air. The objects and people, in turn, warm or cool the surrounding air to create a pleasant indoor climate with uniform temperature distribution.
The advantage of this technology is the direct heating effect it has on the body, without the need to heat another medium first, such as air. As a result, the air temperature of a radiant heated space can typically be 3 deg C lower than that of a conventionally air heated one, while still achieving the same resultant temperature.
Effective everywhere always
Because hot air also rises, heated air accumulates under the cold ceiling where it is wasted, whereas radiant panels are effective everywhere on the ground at all times.
Moreover, unlike air heating, which can take several hours to reach the required temperature, radiant panels react immediately to the hot or cold water entering the panel. This significantly reduces warm up and cool down times and ensures flexibility in temperature control.
With a low storage mass radiant systems are also ideally suited to low-temperature systems, making them ideal for use with renewable technologies.
This combination of functionality, responsiveness and controllability means, that in comparison to conventional air systems, radiant heating can reduce energy consumption in space heating by around 44 per cent.
Radiant panels also offer installation benefits. Designed for large spaces, up to a ceiling height of 30m, radiant panels are lightweight and easy to install.
Available in lengths of up to 7.5m they are ideal for long runs and, being modular in design, can be quickly connected by means of press/screw fittings to help reduce time spent on site. Panels can either be hung independently or fitted directly into an existing grid ceiling.
Made from corrosion-free materials, radiant panels require little or no maintenance. And they can be fitted with integrated lighting and other special solutions to reduce time spent on site.
• The author is brand manager at Zehnder