Internal Illumination

Interior Lighting

Interior lighting is one of the significant design features that is required in museum design. There are different types of artificial light sources with different light types can be used for various spaces. What does the light do? Other than allowing people to see, the appropriate use of different type of lighting produces various atmosphere in a space which will be discussed later.

However, it is a double-edged sword. With other environmental factors such as temperature and humidity, the properties of crafts can be altered drastically throughout their exhibition which leads to deterioration. Therefore, to balance the act of achieving preservation needs of artifacts and form interactive spaces by discovering, exploring and learning which is the goal of a museum, some researches are done.

Research by Ng Xin Ru

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Diagram 1: Material classification based on sensitivity to light

Diagram 1 is the data analysed by CIE which is the International Commission on Illumination on museums in Argentina and Spain. The materials that is extremely susceptible to light cannot be displayed under natural lighting until certain level of natural light is controlled. The lighting level need to be as low as when the sun is just below the horizon in the early morning or sunset in the evening. In this case, the use of artificial lighting is prohibited. For other materials, lighting level can be increased with the condition of considering conservation policy.

Colour Temperature

Colour temperature is a way to describe illumination appearance such as how yellow or blue the light emitted is from the light bulb. The higher the colour temperature, the cooler the resultant light effect. It is an important variable to be considered as it does not only affect the colour appearance of the artifacts or spaces but also the mood communicated to people. Warm light source such as incandescent bulbs have low color temperature which is from 2200K to 3000K and it makes softer and cozier space. On the other hand, cool light sources such as fluorescent lamps have high color temperature which is more than 4000K and aids in concentration.

Diagram 2: Colour temperature from various artificial light sources

While designing lighting system, concept of circadian lighting need to be considered as it follows circadian rhythm by working in harmony with human internal clocks. For instance, in the evening when the day is bright, the space need to give external awareness to people that means outside is still daytime. If daylight is insufficient, the intensity and color of artificial light will be modified according to the natural lighting cycle. This allows visitors to reduce circadian disruption which optimize mood and visual experience in museum while improving sense of wellbeing. At night when there is no daylight, light with low color temperature is suggested as it triggers the production of Melatonin which has relaxing effect. In contrary, high color temperature causes the release of Serotonin which boosts one’s energy level.

Zoning

In order to achieve high energy efficient projects, British Standard Institution which is BSI sets out standards for internal illumination - BS EN 12464-1. The lighting requirements are set based on three basic human needs. Firstly, visual comfort whereby lighting gives people such as workers in museum feelings of wellbeing and thus contributing to their productivity. Next is the visual performance which allow people to fulfil visual tasks under any circumstance for an amount of time and luminaires should enable all work to be carried out safely. The diagram beside shows the lighting levels for spaces in the unit of lux.

The Society of Light and Lighting(SLL) which is part of Chartered Institution of Building Service Engineers (CIBSE) has provided a guide – Lighting Guide (LG7)that aims to ensure adequate amount of lighting and provide a stimulating environment for people. It stated that to allow for energy saving and improving well-being, best practice is to utilize daylight in conjunction with having dimming settings. Otherwise, with the excessive lighting amount and improper located luminaires glare which happens when one part of an interior is much brighter than the ambient brightness may occur to the visitors that has visual discomfort or workers who experiencing disability glare.

Diagram 4 shows that even the material used for finishes is important as they have their own reflectivity. If a space is created for educational purpose in museum, the illumination level would be similar to the data shown in Diagram 4 but it can be adjusted according to different condition. All walls and ceilings should be illuminated. People need to be able to look away into the distance to avoid eye strain. The best scenario here is that they can look outside but if not, there should be a distance to explore, and the walls and ceiling within this view should be lit to a similar level to the task area.

When planning museum lighting, there are some key areas to focus on. All the various ways that artefacts may be displayed, from items placed on the walls or large objects on plinths, to small, intricate pieces inside display cabinets, should be included in a good museum lighting scheme. Museums also hold special or temporary exhibits, so the lighting fixtures for museums should also be considered as exhibitions change, space will need to be altered in the future. All these various display techniques and the broad range of items on display calls for a mixture of different lighting fixtures, from ceiling mounted track lighting to small cabinet lights on poles. Normally lighting for art museum will typically concentrates on wall displays. This can be done by choosing dimmable fixtures with adjustable beam angles that allow lighting technique to adapt to the artifacts on display. A costume on a mannequin may be better viewed using a wide beam angle to create a pool of light, whereas the detail of a small item of jewelry will benefit from a narrow and focused beam.

Artificial illumination can be classified into three main sources through generation and the development of technology that enabled its existence.

First, incandescent lamps which light up by heating the wire filament. Halogen lamp which is also known as tungsten halogen is a type of incandescent lamp filled with a halogen gas such as iodine (I) or bromine (Br). This type of light is not suitable for museum as it emits ultraviolet light which may affect artifacts and heath of everyone in museum so prolonged exposure need to be avoided. Next, fluorescent lighting is the second source of illumination. Although this type of light is an efficient way to provide lighting over a large area and last longer than incandescent bulbs, light that comes from fluorescent bulbs is omnidirectional. It scatters light in all direction and this really wastes energy as only about 60% to 70% of light is used. Moreover, it cannot be frequently switched on and off as this action shortens the lifespan. Lastly, light-emitting diode (LED) lamps. It emits light when electric current passes through the diode and excites the atom inside to high energies.

It is a cost-effective alternative for non-domestic building especially museum which uses light for a long period to replace other type of light source as it is long-lasting and uses less energy to provide same light output.

In conclusion, internal lighting has always been a fundamental feature due to its major role in enhancing visual comfort and aesthetic purposes. The color temperature, space zoning, mounting and types of artificial lighting are all the criteria that should be considered in order to reduce the cost and energy consumption. Daylight should be used as much as possible before installing artificial light as why shouldn’t we use the free gift given by nature?