Monodraught managing director Tony Cull suggests that significant energy savings can be achieved by doing what comes naturally.

Nowadays everyone tries to use less energy because they are aware of the reliance upon nature’s resources.  We all try to maximise efficiency and recycle where possible. It therefore makes sense in this age of high energy cost and global warming to apply energy-saving principles to all areas of our everyday lives, including specifying what comes naturally – for example natural ventilation and natural lighting?

Natural ventilation – using the natural power of the wind – has been around for a very long time. In its simplest form it is ‘single-sided’ e.g. an open window; or cross ventilation which moves air across a room, with openings on either side. Stack ventilation or ‘passive stack ventilation’ goes one step further by creating a stack effect usually with the aid of a chimney. Unfortunately, during hot summer months there is a problem because for a passive stack to work effectively, it is accepted that a 10°C temperature difference between inside and out, which doesn’t help if there is 25°C outside to start with.

However, like many traditional solutions, natural ventilation has developed into a highly sophisticated technology that uses established principles to create a viable alternative to energy-hungry mechanical air conditioning. It will also create a healthy and environmentally-friendly building interior, in contrast to air conditioned buildings, which can produce decidedly unhealthy symptoms such as sore eyes and dry throats in humans, and Sick Building Syndrome in the buildings themselves!

Other disadvantages of mechanical air conditioning include noise; demands for maintenance with changing or cleaning of filters; and often the environment created does not please everyone. But worst of all, mechanical air conditioning uses so much of our precious energy resources.

The latest natural ventilation systems by comparison have none of these disadvantages and are simply and easily controlled. “Top down” ventilation, which uses roof turrets to encapsulate the wind from any direction, has proved to be one of the most reliable and popular forms of natural ventilation simply because it uses the natural elements of wind movement to encapsulate relatively clean, fresh air from above roof level. Wind pressure pushes the fresh air supply through the turrets down into the building, pressurising the space below and forcing out the warmer stale air. This rises naturally to ceiling level and is extracted through the leeward side of the same roof mounted turret. Because the air supply enters and leaves through one roof turret, sophisticated controls can be applied to temperature, CO2, seasonal and daily time settings and, most important of all, provide an effective end-user override facility to ‘open and shut’ control dampers to suit individual requirements. This latter advantage does, however, have an intrinsic overall control, to ensure that the main control panel reverts to its original pre-programmed setting after 20 minutes. Add to this the advantage of a free night-time cooling facility that plunges cooler night air down to floor level causing stale warm air to rise. This action purges the building of stale air and odours leaving interior spaces fresh and cool for the next day.

But what if, as previously mentioned, the temperature outside is 25°C to start with? Even though this year’s ‘Barbeque Summer’ hasn’t materialised yet we are still constantly reminded of the evidence of global warming, so who knows what will happen in 2010 and beyond?

A perceived limitation of natural ventilation is what happens on a hot sunny day when outside temperatures are around 25°C+ and there is little or no wind? What happens also if internal temperatures continue to rise from the effects of electric lighting, computers, photocopiers and other office equipment - and of course, from people themselves?

A recent development in natural ventilation addresses this problem very effectively using another natural energy source – solar power. This innovation gives roof turret ventilation systems a ‘solar boost’, which is used to drive an integral fan that increases the volume of fresh air through the system.

The action of the fan will either improve the natural ventilation rate of the system or, when there is no wind at all, will actually provide a downwash of fresh air. So even when the external temperature is 25°C+ the movement of fresh air through the building creates a welcome adiabatic effect to cool down the occupants, similar to that experienced with a desk fan. This latest generation of natural ventilation systems really is sustainable, energy-free ‘air conditioning’ and the clever thing is – the turrets get a solar boost when the sun is shining – just when ventilation is needed most!

Similarly, natural daylight from roof-mounted tubular skylights or sun pipes – the modern alternative to roof lights – can provide a flood of natural daylight into interior spaces. They are designed to bring natural daylight into just about any building and typically provide approximately three times as much light as conventional rooflights. The highly reflective tube reflects and intensifies sunlight and normal daylight into the space below where it is spread evenly using a diffuser to eliminate glare and heat transfer. Some designs can even be mounted horizontally to pipe light deep into interiors. They can be used in basements!

Where natural daylight is used to replace electric lighting during daylight hours, as much as 75% of electricity costs used for lighting can be saved. As with natural ventilation, natural daylighting is also easily controlled. For example, to maximise energy saving, sensors can be used to monitor natural daylight systems to ensure that electric lighting is only used when lux levels drop below a predetermined level.

And there is more good news. University reports show that natural lighting does significantly improve the working environment, whilst natural lighting in schools has also been shown to improve students’ learning – recording 20% improvements in maths test and 26% in reading tests in one year.

Progression also improved by approximately 20% in well designed classrooms with diffused light. Generally, considerable environmental and health benefits are experienced (natural daylight is known to combat Seasonal Affective Disorder) due to the much improved working environment.

Another energy saving innovation that is beginning to prove its green credentials is a development of intelligent passive cooling that exploits the latest PCM (Phase Change Material) technology to maintain the temperature in a room. As the room temperature increases, the PCM liquefies releasing energy and cooling the air.  When cold, the PCM solidifies capturing energy for the following day. Systems are designed for floor mounting below window level, against an outside wall.  Again, fully automatic intelligent controls are available based on proven technologies. During daytime operation the control system analyses the internal room temperature, the CO2 level and the external air temperature every minute. If internal temperature or CO2 thresholds are exceeded, it automatically allows the introduction of fresh air.

During summer operation, night-time cooling is activated to purge a space with fresh air and at the same time the system pumps PCM through a heat exchanger, solidifying it and storing the coolth for the following day. During winter operation a heat recovery control program is activated and the system is able to capture the residual warmth of the building through the PCM and release this warmth the following day. Looking to the future, this low energy system could ultimately be powered by a solar pack module, to provide a fully zero-carbon alternative to air conditioning in intelligent buildings of the future.

Following a 2-year Carbon Trust sponsored research programme in conjunction with, among others, Nottingham University and CIBA UK plc, one of the first commercial systems is in the final stages of development and offers significant energy conservation potential, as each module has the equivalent thermal mass of 9 tonnes of concrete and uses less energy than a conventional light bulb.

To summarise, in addition to the two ‘certainties‘ in life, we can add a third and a fourth – rising energy costs and diminishing fossil-fuelled energy resources! As energy prices increase, the need to reduce our carbon footprint also increases, so doing what comes naturally really does make sense and has a very important part to play in buildings in the future.