In a modern building daylight can provide most of our lighting needs for the vast majority of the working day. It is therefore unnecessary to spend too much time in designing artificial lighting systems. Introduction It is a common fact that people instinctively prefer natural light than to artificial light. This is usually due to the calming effects and the clarity it offers to which artificial light does not. Also, due to the rising energy costs and today’s climate change concerns, using energy efficiently is now regarded to being financially sensible and now expected within the design on the building.
However it is difficult to justify the cost for the considerable design of day lighting on the basis of energy saving alone. Here I will review and consider the impact that day lighting, also referred to as “natural” or “true light”, has on the human psyche, the heath impacts, benefits and problems both daylight and artificial lighting may cause and in general, whether due to modern buildings now incorporating daylight as a standard factor whether it is necessary to spend a great deal of time in designing artificial lighting systems.
These impacts are reviewed in this paper for buildings that are generally used for offices, retail and other large buildings. Daylight effects in housing have not been considered. Background history At the beginning of the 20th century, daylight was the principal light source in buildings, the artificial lights were merely used to enhance the readily available natural light.
However within the short span of 30 years, by the 1940’s electric lighting had altered the working environment by meeting the majority or in some circumstances all of the occupants’ lighting requirements. During this period there have been continuous developments in the efficiency and types of lamps available. Artificial lighting is today used to provide lighting for the hours of darkness and also to provide visual affects to the interior and now becoming more popular, the exterior of a building.
Until recent years, energy efficiency has been a relatively low priority and low perceived opportunity to building owners and investors. However, these days’ with the dramatic increase and awareness of energy and environmental concerns, Highlighted issues like global warming and reducing carbon footprints for instance have made natural day lighting a rediscovered aspect of building lighting design. The actual physics of day lighting has not changed since its original use, however the building design to employ it has.
Day lighting is often integrated into a building as an architectural statement and for energy savings. However, benefits from day lighting extend beyond architecture and energy. The psychological and physiological aspects of natural light on a person should also be considered. The comforting space and connection to the environment made available to building occupants provide benefits as significant as the energy savings to building owners and managers.
Although through many general studies state publicly that natural day lighting has calming affects there can be no guarantee that daylight will be successful in getting the full benefit of visual performance to the occupiers. Daylight can also cause distress and discomfort through glare and disruption, however this may also apply if the artificial lighting has not been installed correctly and not designed in a constructive approach, these distress and discomforts may also be formed. Impacts of lighting
It is obvious that some form of lighting is required in a building, otherwise productivity would be difficult for the work staff, children in a school or medical workers where lighting can be as important as life or death. The Melbourne government have performed many studies into lighting and the effects of the human body, with the information they gathered Melbourne’s new office building, known as Council House Two (CH2) was constructed. The following is a statement from their website “Light is essential for maintaining human biological rhythms during work, play and sleep.
It adds to our sense of wellbeing, mental health and vitality. Majority of people spend a significant amount of waking time inside artificially lit buildings. We also work to ‘mechanical time’, which is often unrelated to our body’s real needs. The alternative is to work in a well-lit office space, one that balances natural and artificial light and is not only desirable and aesthetically appealing but can improve staff health, efficiency and productivity”. (www. melbourne. vic. gov.
au) Fig 1. a well considered building design, Melbourne’s new office building, known as Council House Two (CH2) incorporating major use of day lighting and ventilation. Both economically and environmentally friendly “Natural” Day lighting Day lighting or natural lighting is admitted into a building by means of openings, whether it is a light shaft, windows or roof light which incorporates glass or an alternative material which is transparent enough to let the light shine though.
The amount of light that is received though the building is generally only a small fraction that is shown outside, this is usually down to the size and the positioning of the viewing hole / openings, whilst other factors that may restrict the daylight entering into the interior of the building are other buildings usually higher than the one the user is in, tall trees and of course the effect of the British weather which is generally inconsistent and unpredictable at times.
Methods can also be made to ensure that the occupants receive as much daylight as possible by Placing workstations or machinery within a 6 – 7 meter radius of the windows while the added use of low-level cabinets and shelving will allow natural light into the building to be maximized. The percentage of light which has eventually overcome all the above aspects are known as the daylight factor. This is a very common and easy to use measure for that particular daylight quality in a room. It describes the ratio of outside luminance over inside luminance, expressed in a per cent.
The higher the daylight factor, the more natural light is available in the room. As stated on the website learn London. (www. learn. londonmet. ac. uk/packages) The rooms in which day lighting is most important should be allocated the preferred positions and orientations, remembering that it is more difficult to screen the low angle sun received on East and West face and that this is where glare and overheating are most likely to occur. The luminance values and distribution required by the activities in each room must be established.
In some spaces uniform lighting is required, in others some variety is desirable. In spaces where people occupy fixed positions like an office plan or a classroom for example, design criteria will have to be more stringent than for rooms where people are free to move in and out of a patch of sunlight, towards or away from a window when the sky clouds over. Below is a table showing the required lux value for each room, lux is the unit of luminance in the International System of Units. It is defined in terms of lumens per meter. It is equal to the illumination of a surface one meter away from a single candle.