Members of the UK Green
Achilles Building Confidence
40% Of UK’s Energy Consumption Is Building Related
It is a staggering fact that over 40% of the United Kingdom’s energy consumption is building related. This in turn produces about half the nation’s CO2 emissions and many other environmentally damaging pollutants which contribute to global warming.
Annual delivered energy consumption in offices can range from under 100 to over 1000 kWh/m² of treated floor area. Although energy is used in buildings for the running of appliances and equipment, lighting but especially heating and cooling are significant both in terms of cost and environmental effect. For the building designer or specifier, there is therefore not only a social obligation to make a building as energy efficient and environmentally friendly as possible, but a strong economic one.
towards Green Buildings
As a result there has been a move towards ‘green’ buildings with natural ventilation and lighting, or at least ones where the amount of air-conditioning and artificial lighting has been significantly reduced. To achieve this, techniques such as solar shading, ventilated facades and daylighting are being employed.
A wide variety of external shading systems are available. In broad terms, however, they can be broken down into two principal categories: motorised venetian or fabric blinds and fixed or adjustable brise-soleil; a highly effective method of taking the 'sting' out of hot summer sun.
Solar heat gain reduction of up to 90%
When fitted internally blinds can reduce solar heat gain by 45% but with external systems this figure rises dramatically to up to 90%. This performance advantage alone can help to recoup the extra cost of external shading systems within a couple of years. There is no doubt that if you can stop the sun hitting the glass in the first place it is cheaper than allowing it to enter the building and throwing it back out by mechanical means since capital costs, such as air-conditioning plant, are reduced as is ongoing energy consumption.
Adjustable and retractable shading systems may be fixed to both new or existing structures. Venetian blinds can be lowered when required and the angle of the louvres adjusted to provide complete shading. Such systems not only combat solar glare and heat gain inside the building but maximise the occupants' visibility. Unlike venetian blinds, fabric roller blinds can only be adjusted between raised or lowered positions.
Often, these systems are linked to automatic controls which may be run by the building management system, however, blinds are generally better operated by a stand alone system with a link to the BMS. This provides maximum flexibility and direct connection to sun sensors.
The right type of shading system for a particular application will depend upon a number of factors including: location and orientation of the building, climatic conditions and specific user requirements.
to find the optimum solution
Finding solutions need not be a problem. At Levolux, we are used to listening to specifiers and providing systems which offer answers to a wide variety of sun shading needs while making best use of natural lighting conditions.
An increasing number of new buildings are being designed to embrace the concept of ventilated facades. These prevent solar gains from reaching the inside of the building during summer months and do not interfere with winter solar gains. At the same time, a clean glass facade is maintained.
The key principal of a ventilated facade is to have an inner and an outer skin to the building with air movement between the two. In this space, blinds may be used and can be automatically controlled depending upon external and internal conditions. Sun heats the air in the void and, in summer months, this warm air is then ventilated from the facade but in the winter, the warm air creates a thermal buffer.
Artificial lighting accounts for up to 50% of electricity consumption
Studies show that up to 50% of electricity usage in commercial buildings relates to artificial lighting which is not only expensive but generates additional heat. Daylighting has evolved to address this by making optimum use of daylight inside the building and developments in shading systems include prismatic louvres which reflect direct sunlight but will allow diffused skylight through from other angles.
Open-plan offices and deeper floor plans normally place a greater reliance on artificial lighting than other schemes. Devices such as light shelves may help to create a more even light giving the impression that the room is brighter than it really is and, as a result, delay staff from switching on artificial lights as daylight levels fall.
Environmental issues relating to building exteriors are a broad subject. Good design cannot only result in energy efficiency, it’s also worth remembering that, when midday summer sunshine sends building temperatures soaring, staff work-levels start to plummet.
When one considers that effective passive environmental control measures can lead to a 1% or 2% increase in productivity, consideration of such issues is very worthwhile.