Lighting & Daylighting

Design which maximises the use of natural light in a building is not just energy efficient - studies have shown that people prefer natural light for work. It is difficult to ascertain how much natural light each window will provide, as weather conditions and natural light are constantly changing, but a south-facing window is likely to provide more light in the UK.

Of course, windows are also a source of heat (and potential over-heating) in summer, and of heat loss in the winter, something to take into account when designing for optimal energy savings.

It is believed that the most energy-efficient lighting solution is to combine daylight with automatic lighting controls which adjust artificial lighting to the minimum necessary levels.  Although these can be expensive to install, energy savings are likely to recoup the expense over the whole life of the equipment. There are also tax incentives in the form of Enhanced Capital Allowances for businesses who wish to install energy-efficient lighting.

Although there are now a range of sophisticated energy-efficient products, simple measures such as the selection of energy-saving bulbs can be both cost effective and environmentally friendly. Other options include:

• Compact fluorescent tubes, which have a longer life-span and use less energy than traditional tubes
• Light sensors, which automatically dim bulb outputs when natural light is available
• Luminaires, which can offer significant savings on capital investment due to their ability to reflect light

Outdoor lighting presents another environmental challenge, and the Chartered Institution of Building Service Engineers has issued the following guidance:

• Only light what is necessary.
• Only light the parts you need to.
• Only light when it is necessary.
• Consider the lighting needs and the health and safety of those having to perform tasks at night outdoors.
• Position lights and choose their distribution so as to avoid spill into the sky and onto neighbouring properties.