Lighting
Layout & Geometry
There is no easy rule of thumb for balancing natural lighting energy savings with cooling load energy increases and useful solar gain increases. Unless advanced building modelling software is used, natural lighting is difficult to model. It has to be borne in mind that for residential applications electric lighting is a minor contributor to their CO2 emissions. However adequate daylighting levels are important for the wellbeing of occupants.
In commercial spaces on the other hand some 25 per cent of total emissions comes from lighting. There is, therefore, a potential benefit in optimising natural lighting at the design stage through detailed modelling.
Fittings
For new-build housing, current regulations demand that a proportion of light fittings must take only low energy light bulbs. However these fittings are more expensive than traditional ones and restrict choice. If incandescent light bulbs are phased out soon, as is currently under discussion in the UK, use of such fittings could be less crucial.
Recent developments in electronic ballast design have led to dimmable Compact Fluorescent Lighting (CFLs) with standard screw and bayonet fittings. These work with conventional switches and dimmer switches, thus improving both usability and acceptability. In fact, there are now satisfactory energy efficient alternatives for almost all types of light fittings. Even spot lighting is available in GU10-type compact fluorescent bulbs, though these are rapidly being replaced by the Light Emitting Diode (LED) products coming onto the market. LED lamps have evolved rapidly over a very short space of time from purely ornamental applications to viable lighting applications. Further developments are expected. For a view of current and future technology see: Market Transformation Programme: BNDL101: New lighting technologies
Controls
How these fittings are controlled is particularly important in the case of commercial buildings: PIR movement detectors, daylight detectors and zoning can go a long way in minimising energy and carbon emissions.
Behaviour
The most energy efficient lighting will save nothing if it is left on unnecessarily. There is a myth that energy efficient light bulbs must not be switched on and off frequently. While this may indeed have a small effect on the lifespan of a bulb, the carbon emitted during unnecessary use far outweighs any such benefits. It is also important to ensure that occupants are aware of permissions and duties with regard to switching off lights. This applies in particular to non-residential premises where switches may be in obscure places or it is assumed that automatic controls are in place.
