| Solar Shading for a Greener World |
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by Richard Guthrie, Guthrie Douglas Ltd The U.N. Conference on climate change in December 2005 and the entry into force of the Kyoto protocol have highlighted the need to ensure action is taken now to limit carbon emissions and invest in long-term technologies that will help build a sustainable environment. Governments worldwide are accepting the need to come together and pledge reductions to these emissions on a global scale to reduce the threat from global warming. Legislation is being drawn up in each country participating in the discussions to make sure this happens, and in the UK for example this legislation clearly encourages the use of solar shading to help achieve these aims. Since buildings are a major source of carbon emissions, the trend to low or zero carbon emissions already plays an important role in their design throughout Europe and worldwide. Solar shading products provide an effective way of ensuring that buildings comply with current legislation to cut down on harmful emissions that could cause irreversible climate change within a generation Within England and Wales the 2006 Building Regulations which come into effect from 6th April, clearly recognise the need to conserve fuel and power by limiting excessive solar gains. Each building will have a predicted rate of CO2 emissions known as the BER, which must not be greater than the target rate or TER. The use of air conditioning will be taken into account when calculating the BER but where no cooling is provided there are criteria for the performance of passive measures which should be employed to prevent overheating. Since carbon emissions associated with the operation of cooling systems are comparatively severe, it is important to consider specifying solar shading at the earliest stage of building design to help ensure the TER is not exceeded. Cooling systems are not the only generators of CO2 in buildings. The power requirements for the lighting system should also be taken into consideration. The energy for electric lighting will increase as the window area reduces it so it is important to maintain a balance between glazing surface area and natural day lighting. When thinking about solar shading systems, external systems seem the natural choice due to their higher efficiency. External systems can however be combined with additional internal ones in the same building for effective local glare control. In addition to this, fixed external systems, typically the brise soleil which have been fashionable in recent years, only provide a partial solution in that they are permanently in place and will tend to increase the lighting requirement on dull days increasing emissions unnecessarily. Operable systems such as aluminium louvres and external venetian blinds are highly efficient being easy to open or close to improve internal lighting conditions. Depending on the construction design a fabric solution is also possible. There is a very wide choice of fabrics available nowadays suitable for external applications, as well as new ranges coming onto the market which are 100% PVC free. Unlike solid aluminium louvres, fabrics allow the designer to choose a solar transmission factor to suit the use and occupancy of a building. A design studio with extensive VDU usage would for example require a different solution from a gallery displaying sculpture. The openness of a fabric also allows partial through visibility keeping those inside the building in touch with the exterior environment. An operable system will naturally fail to cut down on unnecessary emissions if the blinds are not deployed or retracted at the right times. By virtue of their position on a building however, most external systems are motorised which facilitates automatic control. Modern motors operating shading systems are easy to network together to allow full automatic control, whether by simple wireless connections suitable for smaller installations or modern bus systems which are found in many larger commercial buildings. The latest developments in control systems, such as PILOTpc which run on computer networks, calculate solar position at a given time of day and, using measurements of wind speed, sunlight intensity, rain etc, determine the optimum conditions for the deployment of the shading system. For today's architect, solar shading is a critical consideration that cannot be overlooked if we are to seriously start controlling the carbon footprint we are leaving on our planet. Their importance cannot be understated as their incorporation into buildings both old and new can make a significant saving in energy costs as well as a significant contribution to the well being of future generations.
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