Making a decision between heat emitters

Radiant panels, fan convectors

Today there is a range of heat emitters available for commercial buildings. Steve Gage, sales director at SPC, a UK based manufacturer and supplier of heating and cooling equipment, explains more about fan convectors and radiant panels, and suggests that making a decision between them is often based on building type.

Increased focus on energy efficiency has meant that the heating sector has seen a huge amount of new product development in recent years – meaning there are many solutions for specifiers, consultants and heating engineers to consider. As well as making a choice between installing high efficiency boilers or new technologies such as heat pumps, a decision also has to be made about which type of heat emitter will be most suitable.

In our experience, the application often dictates the solution, as one size does not fit all. A good example is an old school building. Because of their design, ageing schools – which often date back to Victorian times – are more suited to traditional heat emitters such as fan convectors. But the good news is that updating them to modern versions can still generate significant energy savings.

Victorian school buildings are often draughty, have high ceilings, have little or no insulation and potentially lack double glazing. This is a recipe for heat loss, and means classrooms can be difficult to heat.

Fan convectors have long been seen as a staple heating solution for school classrooms. They are popular because they heat a space up extremely quickly – emitting three to four times as much heat as a radiator, they can take a room from cold to comfortably warm in about 15 minutes. In terms of heating up a space quickly and efficiently they are actually difficult to beat. In fact, Building Bulletin 87 (BB87) states that fan convectors have a much faster response time compared to other heating technologies.

Modern fan convectors have become more efficient, so updating them will deliver energy and carbon savings. In a drive to improve efficiencies, SPC uses EC motors as standard in our Belgravia fan convectors; this lowers the specific fan power (SFP) and therefore saves energy. In addition, in recent years fan convectors have become more aesthetically appealing; our Belgravia Supreme, for example, has a sleek, stylish design. Furthermore, the Supreme doesn’t have any sharp edges, making it ideal for classrooms.

Fan convectors require only a small amount of wall space and are simple and cost-effective to install, and replacing like-for-like minimises redecoration costs. As well as being an ideal solution for school refurbishment projects, fan convectors are suitable for other existing commercial buildings, such as shops and offices.

In highly insulated modern buildings, which are easier to heat, it will probably be more appropriate and efficient to fit radiant panels. Unobtrusively installed in a ceiling, radiant panels maximise wall and floor space and help save energy and money, while creating a more comfortable environment for occupants.

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. The way the sun heats the earth is a good example of radiant heating.

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 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 is installed in a room and 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.

Radiators generally distribute 80 per cent of their output via convection and only 20 per cent via radiant heating. This means that for a radiator to heat a room it must first warm itself and then the air around it. By avoiding the need to heat all of the air within a room, radiant heating systems can offer considerable energy savings. 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 half an hour in advance.

There are many different radiant heat panels available, and different manufacturers will use subtly different methods. However, the basic concept is the same; water is distributed throughout the metal panel via a tube, designed to provide the maximum surface area and therefore thermal contact. The water heats the tube, and the tube heats the panel. SPC’s ThermaTile Plus consists of a special corrugated aluminium panel of patented design and a continuous copper tube fixed in a serpentine arrangement on the upper surface.

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 the University of Stuttgart (the only test chamber in Europe certified to conduct this testing) stating the output of a 3m x 600mm panel.

Services can be run through the ceiling void and do not need to be dropped down to a lower level, so installation costs are reduced. 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.

In addition, eliminating the need for surface temperature radiators at ground level creates a safer environment, and reduces the risk of accidental or deliberate damage. The reduced convection also results in lower dust levels, which is beneficial for allergy sufferers, and helps save on cleaning and maintenance costs.

The other benefit of radiant panels is that designers have considerable freedom to create bespoke systems. Rafts, foils, free-hanging units, non-standard shapes and a variety of colours can be used to create striking aesthetics.

Both fan convectors and radiant panels are fed by low pressure hot water; this can be derived from a boiler (which can be served by a range of fuels) or new technologies such as heat pumps. They can both provide a comfortable environment in commercial applications – making a decision between them should be based on the characteristics of the building, and how efficiently the heat emitter will perform in that particular space.

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