Radiant panels offer many benefits; they work well with lower temperature heating systems, save energy and money, and create a more comfortable environment for occupants. And, being unobtrusively installed within a ceiling, they also maximise wall and floor space. Dave Jones, product manager – radiant at SPC, explains more.
Radiant heat is a form of electromagnetic radiation, falling between ultra-violet and infra-red on the electromagnetic spectrum. Though it is invisible to the human eye, it shares the characteristics of light. It penetrates clean air without energy loss or deterioration, exchanging heat with any object of a lower temperature; this is similar to the way the sun heats the earth.
While there are many different radiant heat panels available, and different manufacturers use subtly different methods, the basic concept is the same; water is distributed through a metal panel via waterways attached to the rear. SPC’s ThermaTile Plus consists of a special 5.5mm corrugated aluminium panel of patented design, with copper waterways attached to the rear by extruded aluminium pipe carriers.
In recent years, the benefits that radiant panels offer the owners, managers and occupiers of commercial and public sector buildings have become more widely understood – so much so they are often regarded as a first choice system solution.
One reason for their growing popularity is that they work well with lower temperature heating systems, such as condensing boilers and low carbon/renewable technologies – which the UK has been moving towards. When lower system temperatures are used, traditional heat emitters that work via convection – i.e. radiators, which generally distribute 80 per cent of their output via convection – become less viable and less efficient as a heating solution. Convection becomes too slow in response, and the bigger the space the slower the performance, as convectors must warm the whole air mass to achieve a comfortable temperature.
If radiators are used they have to become much larger to compensate for the lower system temperatures, and often there isn’t enough wall space available. In addition, large air changes result in lost energy and money and poor controllability.
Radiant panels installed in ceilings have become an increasingly viable alternative, with large area, low intensity radiant heat offering the most comfortable indoor environment for the human body. Radiant heat can be used to improve a room’s comfort levels, with the panels providing evenly distributed warmth by shining heat on the objects below. As these objects are at a lower temperature, they absorb the heat and conduct it, increasing in temperature. These objects in turn become low surface temperature ‘radiators’ – giving off lower levels of radiant heat and slowly warming the air within the room by convection.
The high radiant values contribute to a higher ‘resultant temperature’ in a room. The air temperature within a radiant heated room can be up to 3°C lower than in a room heated by alternative means. For example, if a radiator installed in a room provides an air temperature of 21°C and a radiant value of 17°C, it gives a resultant temperature of 19°C. If the radiator is replaced with a radiant panel, the air temperature can be lowered to 16°C and the radiant value increased to 22°C to achieve the same resultant temperature.
For a radiator to heat a room it must first warm itself and then the air around it – but the higher radiant values of radiant panels offer instant heat while the air is reaching the desired temperature. A radiator system may need to be switched on two or three hours before the occupants arrive, whereas a radiant heating system would only need to be switched on 30 minutes in advance.
The bigger the space, the greater the savings will be compared to convective systems. When heating a large space, such as a sports hall, it may be possible to offer a 40 per cent energy saving with a radiant system.
In addition, eliminating the need for surface temperature radiators at ground level creates a safer environment, lowers the risk of damage and reduces maintenance. The reduced convection also results in lower dust levels, which is beneficial for allergy sufferers, and helps save on cleaning and maintenance costs.
It is worth mentioning that radiant panels resting idle in the summer can be used to provide cost-effective cooling or partial cooling. For example, radiant panels installed in a typical sports hall and providing 40kW of heating could also provide 16kW of cooling. Radiant cooling is a passive approach; the radiant panel itself is the coolest item in the room and as the warmer items create convection the warmer air rises. This air then passes over the surface of the panel and cools down. It becomes heavier and drops back to the lower level, aiding natural convection and enhancing the cooling effect.
A further benefit of radiant panels is that designers have considerable freedom to create bespoke systems. While around 50 per cent of the current UK market for radiant panels comprises standard installations in T-bar suspended ceilings (mainly in health, education and office applications), the remaining market is for projects with more technical, project specific or aesthetic requirements. Rafts, foils, free-hanging units, non-standard shapes and a variety of colours can be used to create striking effects, and it is possible to add acoustics, lighting and other services to radiant panels.
No matter whether a standard or bespoke design is chosen, the positioning of panels is a key consideration in ensuring that the heat produced will spread evenly throughout the space – we can provide advice and assistance on mounting height, location and flow rates. If the cooling function is to be used, separate controls and dew point sensors will be required and the pipework design will need to be based on the cooling requirements.
It is important to note there is only one specification applicable to testing the output of a radiant panel: BS EN 14037. Any manufacturer that has tested its product will be able to supply a BS EN 14037 certificate from one of the two test chambers certified to conduct this testing stating the output of a 3m x 600mm panel.
On a daily basis we see more and more interest from consultants in radiant heating, cooling and integrated services, and, bearing all the benefits in mind, we can only expect this trend to rise.
For further information please visit www.spc-hvac.co.uk.