Legislation in South Africa will in future require buildings to be more energy efficient, with new standards on energy efficiency being developed by the South African Bureau of Standards (SABS). Some municipalities are looking at by-laws and incentives schemes to reduce energy consumption in buildings.

Dr Jeremy Gibberd of the CSIR provides information on research to produce policy guidelines for use in the design of new buildings that are energy efficient.

In line with the concept of green buildings, researchers concentrated on passive environmental control, day lighting and renewable energy such as solar power, rather than mechanical systems such as air conditioning.

In designing green buildings, energy efficiency should influence all aspects of the building, including the choice of site, the size and shape of the building, windows and roofs, and type of mechanical systems specified as well as interior layouts.

Environmental conditions such as temperature, humidity, daylight and ventilation have a direct bearing on human health and productivity. In achieving energy efficiency, it is important not to produce unhealthy or unsafe environments.

Solar radiation
Solar radiation levels in South Africa are among the highest in the world. Research shows that average daily solar radiation varies between 4,5 and 7 kilowatt hours (kWh) per m2. Even in winter, parts of the country receive more than 6,5 kWh/m2 per day. The duration of sunshine is also high. This free resource can be used in passive environmental control strategies, solar water heaters and photovoltaic systems to improve energy efficiency in buildings.

Location
Green buildings should be located in such a way that unwanted heat losses or gains are avoided. In general, the long section of buildings should be orientated to about 15 degrees of due north. The north-facing part should be maximised, and the length of the building facing east and west minimised. This enables good access to sunlight for the north facade, good access to daylight through the north and south facades, and reduces unwanted heat gain from early morning and late afternoon sunshine on the east and west facades.

Shading devices should be used to avoid unwanted heat gains. In general, horizontal shading elements are appropriate on northern facades and vertical moveable louvers are suitable on east and west facades.

Lighting and equipment
Electrical lighting systems vary and it is important to select the most appropriate system for applications. One should consider light level requirements, safety, energy efficiency of systems, colour rendering and maintenance. The use of tungsten and halogen lamps should be minimised as these are the least energy efficient. Dust and dirt on light fittings and lamps can reduce their effectiveness by up to 40%.

Increasingly, office equipment has energy ratings and includes energy saving features. Flat screen monitors emit less heat, use less energy and space than conventional monitors, while lap-tops use about 25% of the energy used by conventional desktop computers.

Luke Osburn from the CSIR provides some more information on lighting:
Lighting consumes about 29-35% of the energy used within office space while lighting only consumes about 11% of the energy used in homes. Through good design of lighting systems, the lighting load can be reduced by more than half within both environments. These estimates can vary significantly in relation to the particular shape, size and function of buildings.

Office environments operate differently to residential environments. Offices have a very high level of occupancy during office hours and are then largely unoccupied, while residential buildings have highly sporadic occupancy levels throughout the year.

• Fluorescent tubes
  Fluorescent tubes should be used wherever possible, as they consume roughly a quarter of the power that incandescent bulbs need to produce the same amount of light. Because the fluorescent tubes are more energy efficient, they also produce significantly less heat. A variety of fluorescent tubes are available and one should select the most appropriate fluorescent tubes for different applications.
  
  A fluorescent lamp or tube is a gas-discharge lamp that uses electricity to excite mercury vapour. The mercury atoms produce short-wave ultraviolet light which causes a phosphor to fluoresce, producing visible light. Higher quality phosphors allow manufacturers to use less mercury within the construction of the tube. Care should be taken for the proper and correct disposal of fluorescent tubes.
  
  
• Light-emitting diodes
  Light-emitting diodes (LEDs) have a very long life, are vibration resistant, produce a highly directional light and are very small. However, they need to become more cost-effective before their use becomes widespread. Despite their high capital cost, they are, however, the most efficient and cost-effective lighting solution within certain niche applications, such as when used as display lighting.
  
  
• Task lighting
  Particular tasks, such as reading, writing or drawing, require higher than normal lighting levels to be performed comfortably. Such lighting levels need not be supplied to the whole area but task lighting can be supplied in those areas where such tasks are performed. Consequently, a lower overall lighting level can be maintained with dedicated task lighting that should only be used as it is needed.
  
  Task lighting can be used in offices, homes, kitchens and studies, and is particularly effective in an open-office plan structure where each person has dedicated lighting for use as needed.