People enjoy daylight in particular but only if it does not distract from the task in hand. People are tolerant of varying light levels if they know that the light is daylight. Daylighting has excellent direction, colour rendering and colour appearance characteristics. It can create illuminance levels which exceed the minimum standards for the particular sport and make it easier to play, as perception of detail increases with increasing illuminance. However, care needs to be taken with glare control.

Capital & Running Costs

Capital cost and running costs are important to the long term viability of a sports facility. Dry sports centres use 11% of their total energy for lighting, and savings to be gained by the correct use of daylighting are significant in economic and environmental terms. Electricity costing is more expensive during the day and hence savings during daylit hours are particularly economic. However, capital costs for incorporating daylighting can be 2 - 3 times that of a plain wall or roof, and maintenance costs are increased. It is therefore difficult to justify on purely economic grounds and it is important that amenity benefits are appreciated and energy efficiency maximised.

Using daylighting and good quality controls and artificial lighting is inevitably more expensive than alternatives.

It is therefore important to be able to maximise, calculate and communicate the cost in use benefits as well as the benefits of improved quality of internal environments.

Calculations methods are available with varying degrees of sophistication. The more sophisticated methods do not always transpose well for use in sports facilities because sports halls cannot take advantage of solar gain and because adaptation is a crucial aspect.

Understanding Daylighting of Sports Halls

Daylight Qualities for Sports

Light Quality

Good lighting enhances the quality of a sports hall and contributes to creating an atmosphere which can add to the enjoyment of play. Both artificial and natural light needs to be of a high standard if players are to be satisfied. Colour and brightness of lighting, its interaction with surface colours, patterns and reflectances are all important aspects.

People generally prefer a space to be ‘visually light’ and ‘visually interesting’. This is brought about by designing for all surfaces to receive some light, but not all surfaces to be of the same illuminance. Contrasts and colours are welcome. However, too much light coming from a single source, a bright light or relatively small window in a large room, will make it appear gloomy even if it is lit to the correct level. Bright sources also cause glare. In sports facilities this sets up particular constraints especially for competitive play.

Energy efficiency from lighting design relies on the interplay of a number of effects including

• the availability of usable natural lighting;

• how the building is used and managed;

• choice of lamp and luminaire;

• maintenance, decorating and cleaning regimes of lamps, luminaires and

surfaces;

• heat gains and losses through glazed areas, and the extent of personal and

overriding control including glare management.

All lighting is subject to diminishing output because of ageing and dirt on windows, lamps, luminaires and surfaces. It is important to understand and communicate an appropriate and responsible approach to maintenance at the outset. All of these aspects need to be considered and compared at the design stage if savings are to be maximised.

Good lighting controls are amongst the most cost effective energy measures. An average sports centre could reduce its energy consumption by 30% with better controls, and payback on investment in less than 3 years.

Optimum glazing

The benefits of daylight, and the savings in artificial lighting use, must be weighed up against the energy penalties of rooflights or north facing windows. Sports halls differ from many other buildings due to the need to exclude solar ingress. Hence they are unable to make use of passive solar gains which could also contribute to energy efficiency. A reasonable estimate would be a maximum of 20% glazing area for North facing windows and an optimum of approximately 9% of the floor area for rooflights. See LT Method on Page 15.

Windows should be well insulated to compensate for the lack of solar gain. A minimum specification would be double-glazing and low-e coating. Gas filled cavities and exceptionally low U-values, are usually outside the feasibility of most halls. More coatings and layers of glass reduce the light transmission, but improve the thermal performance.