One of the problems has been in the ‘cheap energy policy’ of
Government; there may be other good reasons for this, but it has led in
the past to a prodigal use of cheap energy, and it is only recently, with a
looming energy crisis, that government has woken up to the vital need
for savings to be made.
The first line of defence must be in avoidance of waste; for how many
times do we pass a building with every light burning in the middle of the
day when daylight is quite adequate, or after dark when the building is
largely unoccupied. The total amount of energy wasted on a daily basis
may not have been calculated, but it is considerable and arguably equals
the amount of savings which can be made in other ways.
A particular example of this might be in transport buildings where
artificial light is used all day irrespective of the level of daylight. There is
no doubt a need for the level of daylight never to drop below the
statutory design level, but this can be solved by adopting a system of
control which links artificial light to the available daylight to ensure that
the design level is maintained, whilst allowing significant reductions in
the use of artificial light, which can be off for most of the day.
DAYLIGHT
The most obvious vehicle for energy saving in buildings is in exploiting
the most abundant source of light available to us – daylight. Environ-
mentally conscious assessments of building design are recognizing that
daylight (and natural fresh air) is an important commodity and should be
exploited to the full. Generally, people when asked, always prefer to
work in a daylit environment. There is a growing acknowledgement that
daylight produces positive effects, both physiological and psychological.
Forms of control are necessary to limit the potentially excessive levels
of daylight, if it is not to become a nuisance, particularly on bright sunny
days. A wide range of devices are available, from relatively inexpensive
and simple internal blinds (roller, venetian etc.) through to high tech,
computer-controlled heliodens, which track the sun.
Whilst a daylighting strategy will be needed in those buildings where a
decision to provide air-conditioning has been adopted, it is in those
buildings described as ‘passive’ where the greatest savings can be made.
A passive building is one in which the greatest use is made of natural
resources... natural light, solar power and ventilation derived from
making use of the natural environment. Nature cannot provide all that is
necessary, and even during the day there may well be a need for some
additional energy use, in terms of lighting from artificial sources, or
ventilation from some form of fan assistance, whilst in terms of solar
power, this can be used to advantage.
CONTROLS
The careful introduction of lighting controls can ensure that the
maximum use is made of the available daylight; so that the amount of
artificial light is reduced automatically when all, or most of it, is no longer
required to meet the design level.
The term ‘daylight linking’ has been used already, and this perhaps
needs some explanation. It is used in the sense that the artificial lighting
in a building is planned and controlled to support the natural light
40 Daylighting: Natural Light in Architecture