Architectural Lighting

Synonyms

Lighting design

Definition

Architectural lighting design is the design and implementation of daylight and electric lighting provision in urban and architectural environments. This process requires conceptual thinking, design development, and illuminating engineering to produce lit environments for people’s work and leisure.

Lighting Quality

The built environment in which people live and work is composed of a variety of building types. In a shopping mall, retail units are expected to be colorful and attractive. In an art gallery, it is necessary to be able to appreciate the color and detail in a painting, and when walking in the city, people expect to remain safe and secure. All these impressions can be dramatically affected by the lighting. Boyce has suggested that bad lighting “does not allow you to see what you need to see, quickly and easily and/or causes you discomfort” [1]. If the lighting designer overcomes these problems, then they can produce – at best – indifferent lighting. Only when the configuration of the windows and surfaces or the characteristics of the lighting installation “lift the spirits”, can the environment be described as good lighting.

The task of the lighting designer or a lighting engineer is to determine the character of a lit space, whether it be a street, a townscape, or a room, and then to arrange the sources of light, be they daylight or electric light, to achieve this desired character.

Objectives of Design

The purpose of lighting is to provide for the needs of people who are going to use the built environment that is being created, and any person designing the lighting will wish to create a quality lit environment. However, this raises the question about what constitutes good quality lighting? To answer that question, the needs of the people who are going to use the building that is to be lit require consideration. In general terms, the users of a building are going to want lighting so that they can see things easily, they will require the lighting to set the correct ambience, and if they are going to remain in the building for long periods, they may well benefit from the biological impact that the lighting may have on their endocrine systems. These topics are covered in more detail in the following sections.

Light for Seeing

Before considering what sort of lighting is required, it is first essential to consider what the occupants of a building need to see and what the consequences are of them not being able to see. Consider two cases: a surgeon undertaking heart surgery and an office junior doing a filing task. Both of them need to be able to see small objects – in the case of the surgeon, this may be small blood vessels; whereas, for the office junior, he has to read the small text on the documents he is working with. However, the office junior is normally dealing with high contrast printed text, while the surgeon has the problem of distinguishing objects that are very similar in color and reflectance. Moreover, if the surgeon makes a mistake, it could kill a patient, but an error in filing can be easily rectified. Thus, it is normal to have more than ten times as much light available in an operating theatre compared to an office.

Selecting an appropriate level of lighting for a given visual task is bound to be complex as a number of factors need to be considered. These include the complexity of the visual task, the visual acuity of the person performing the task, the length of time for which the task is performed, and the consequences of any mistakes. These factors need to be set against the cost of providing the lighting and the other negative consequences of providing lighting such as energy use and associated greenhouse gas emissions.

To help lighting designers in the selection of appropriate lighting conditions, there are a number of codes and standards available which provide recommendations for the lighting conditions considered necessary for a whole range of different tasks. These documents have evolved over a number of years and in general provide a consensus view of the lighting needs in a typical installation. However, the lighting requirements for every installation are potentially different and so the guidance provided by codes and standards should usually be regarded as a starting point from which the design may be developed; however, there are occasionally situations where the national regulations insist that particular illuminance values are used in given circumstances. Good examples of such codes are the IES Handbook [2], the SLL Code for Lighting [3], and ISO 8995-1:2002 [4].

While considering the required illuminance necessary for a particular task, it is also important to consider other factors such as freedom from glare and the necessary color properties of the light sources used. Most codes and standards also give advice on these issues.

Setting the Ambience

Every lighting installation sends a message to the users of the building; it is the art of good lighting design to ensure that this message complements the message sent by the architecture and that the overall message is appropriate to the use of the building. Consider the lighting in a supermarket and compare it with the lighting in an up-market boutique. In many ways, the lighting has a similar job to do – it must show off the goods in the store so that people choose to buy them. However, the style of the lighting is radically different as supermarket style lighting in the boutique would send entirely the wrong message to potential customers.

There is no simple way of providing lighting that perfectly provides the correct message for a given environment. There have been many studies into how to characterize the lit environment of places that are considered to be well lit, and in general, the results have been patchy and limited in validity to the environment in which they were assessed. Section “A Framework for Design” gives some basic advice, but it is always going to involve a series of complex subjective judgments to get the lighting right and the reliance on simple codes will not suffice.

Biological Impact

The nonvisual or biological effects of light have their biggest impact on the regulation of the human sleep/wake cycle. Exposure to high levels of light may be used to shift the time of peoples’ body clocks and may also be used to boost the alertness of people. These biological effects happen naturally to people in an outdoor environment; however, in many interiors, there is not sufficient light to provide the necessary stimulus to the human endocrine system.

The most logical way to resolve the problem is to provide interiors with good levels of daylight. Light sources may be used, biased toward the blue and blue/green regions of the visible spectrum (within acceptable safety limits), if the objective of the design is to promote the nonimage-forming impacts of light [5].

A Framework for Design

The objective for anyone trying to design lighting is to provide good quality lighting. The construction of a new building or the refurbishment of an existing one comprises a series of construction stages from design through construction to the final use of the building or area. Lighting should be designed by someone who has the ability to make the necessary aesthetic judgments about how the lighting will impact on the space being lit while at the same time engineering the lighting equipment into a functioning system. Therefore, the lighting designer or lighting engineer can make a particular contribution or intervention within the design phase. Here, a lighting design concept is proposed where outline proposals for the arrangement of structural and building services are made. The design is then developed in detail to decide on the relationship between the electric lighting systems and the daylighting, and finally a technical specification is drawn up to coordinate the various components and architectural elements.

At each of these stages, the designer will be considering a variety of factors. Veitch has suggested that designers should consider the well-being of the individual user, the integration with the architecture, and the economics of the lighting installation [6]. Loe has proposed a useful variation in a framework for design [7], which comprises the following elements (Fig. 1).

Fig. 1

A framework for lighting design (after Loe). The relative weight given to each element of the framework depends upon the requirements of the lighting design

Lighting for visual function: The lighting should enable users to undertake visual tasks without visual discomfort. Recommendations are made concerning the level of light on the task (illuminance) and the uniformity of light on the task. It is also important to prevent unwanted brightness in the visual field (the control of glare).

Lighting for visual amenity: People prefer an architectural room or urban space to contain a degree of visual lightness (a sense of lightness and airiness) and visual interest (a variation in light and shade). The color appearance of the space should be appropriate for the application, e.g., warm and inviting or cool and professional. The objects and people in the space need to be lit pleasingly.

Energy efficiency and sustainability in lighting: The lighting installation must contribute to sustainability by maximizing the use of daylighting and ensuring that energy efficient light sources and light fittings are specified. Reducing energy consumption is a matter of reducing the power load of the lighting components and the hours of use. This can be achieved by the effective use of lighting control systems (switching, dimming, and linking to daylight levels).

Lighting installation maintenance: The lighting designer or engineer must specify a lighting installation that can be easily maintained by the client or user. It should be easy to clean and relamp the fittings to ensure that the installation continues to deliver the appropriate lighting. Poor maintenance of an installation will lead to some of the lighting points failing and this sends the message that no one cares about the space.

Lighting costs: The cost of the installation needs to be controlled and a distinction is made between capital costs (for the original lighting equipment) and running costs (the cost of operating the lighting system as designed).

Architectural integration: An understanding of the intent of the architect and the character of the space in terms of dimensions, finishes, textures, and materials is essential. Only then can electric lighting systems be properly integrated into the fabric of the building to produce the appropriate lighting effect.

These factors are described in greater detail in the SLL Lighting Handbook [8]. It should be noted that they are occasionally legal requirements for lighting in certain areas.

Daylighting

It is useful to think of the elements of the city and the town and the constituent buildings as being under the vast dome of the sky. In many climates, there will be days in which this dome is covered by a thick layer of cloud – the fully overcast sky, which might be termed the diffuse component. As the conditions change, the clouds begin to thin and the sun emerges. This source has a very different character – a sharp beam and the ability to create shadows – this may be called the direct component. These two components of daylighting are varying continually throughout the day and throughout the year.

The lighting designer works at different scales of analysis. For example, the designer might seek to optimize the spacing between apartment blocks to ensure that certain apartments are not restricted in the amount of light that they receive. The designer might also seek to ensure that courtyards or plazas receive enough sunlight or are shaded in certain climates. Simulation software has the capability to demonstrate the effect of sun position on buildings. Stereographic sun paths are available to show the passage of the sun in the sky (Fig. 2.).

Fig. 2

A plot of the sun’s position in the sky for London (51°N Latitude) denoted by its azimuth angle in plan and altitude above the horizon

The lighting designer can also work in conjunction with the architect to ensure that the individual rooms and spaces within a building receive sufficient daylighting. The traditional way to pierce the solid wall of a building is by a vertical window. The clerestory window and the rooflight provide ways of allowing daylight to enter the building to provide a different character to the space. This is because they are facing different parts of the sky. The atrium is a useful device, historically and in contemporary buildings, to let natural light deep into the building. It is also possible to “borrow” light from one space to another using transparent partitions.

Contemporary buildings have a framed steel or concrete structure in which the structure defines the architecture. The introduction of daylight into the building thus becomes a result of the structural decisions that have been made. This is the province of facade engineering whereby the transparent partitions that clothe the structure are then subject to varying architectural treatment in terms of the choice and specification of the glazing (solar control or electrochromic materials) and whether shading is to be added (louvres and brise-soleil). It is at this point that daylight availability is estimated by calculation of the daylight factor or methods of calculation of cumulative daylight exposure. The European standard for daylight in buildings [9] provides guidance on the necessary qualities of daylight to necessary to provide a successfully daylit space.

When designing the daylight in a building, it is also important to consider the quality of the view out (and in) that the windows may give.

Electric Lighting

There are a plethora of new technologies for lighting, e.g., light-emitting diodes (LEDs), and a variety of lamp technologies including high-pressure discharge lamps, fluorescent lamps, and incandescent lamps. The designer has the ability to control both the intensity and the color of the light that is emitted from these sources.

Consider the public square in the town or city. An appropriate choice of lamp on an amenity lighting column can attractively reveal the features on the faces of fellow street users to ensure safety and security, and the appropriate color choice can dynamically reveal the city.

The architectural façade can take a variety of forms: neoclassical, turn of the century, international modern, or contemporary. It is the task of the lighting designer to reveal the characteristics of the architecture without distortion, to complement and enhance the architectural detail. It is important to ensure also that each architectural element is read as a whole – from the base to the roof. Again the judicious choice of color and intensity of the light source in conjunction with an appropriate lighting fitting can ensure that the architectural intention is maintained.

Moving indoors the choice of light source remains critical in terms of its color, its life, and its efficiency. Such sources are housed within light fittings (luminaires) – used individually or more typically in arrays to provide layers of lighting or inbuilt into the architecture.

An individual luminaire can be used to accent individual features, and arrays of luminaires (linear and modular in form) can be arranged within the various architectural spaces to provide lighting for tasks and to reveal the architecture of the space with its characteristic finishes and materials. Care is taken by the designer to ensure that the user of the space is not subject to unwanted glare from the fittings and that the overall brightness of a sequence of spaces from one to the next is kept within reasonable bounds (adaptation).

The design of an individual luminaire is a complex process in itself. It must be designed to house a particular light source which might be spherical, linear, or elliptical. The flux from the source must be possibly redirected into the required direction by the use of a reflector and then the beam from the lamp must be further refined by optical elements such as diffusers, lenses, or louvres. The fitting must be electrically safe, must not overheat, and be mechanically strong – these are common requirements even though the physical form of the luminaire might be quite different cf. a downlighter in a conference center to a street lighting bollard. The designer must also consider the appearance of the fitting when it is lit and when it is unlit and ensure that the fittings integrate well with the architectural character of the space.

Endpiece

Architectural lighting has great power. Think of the dramatic daylighting of the Pantheon in Rome (Fig. 3) or the harmonious integration of the lighting of the city of Lyon at night (Fig. 4) or the dynamic lighting of a modern luminous media façade (Fig. 5). But with that power comes responsibility – responsibility that can be accepted by the designer in designing lighting that promotes human comfort and satisfaction.

Fig. 3

The Pantheon in Rome

Fig. 4

The City of Lyon at night

Fig. 5

A luminous media façade

Cross-References

• Light Emitting Diode, LED

• Lighting Controls