Architectural lighting design is a field within architecture and architectural engineering that concerns itself primarily with the illumination of buildings. The objective of architectural lighting design is to obtain sufficient light for the purposes of the building, balancing factors of initial and operating cost, appearance, and energy efficiency. Lighting designers are often specialists who must understand the physics of light production and distribution, and the physiology and psychology of light perception by humans.[1] Architectural lighting design is generally concerned with the permanent illumination of a structure. Concert and theatrical lighting have different purposes and practitioners.
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Comprehensive lighting design requires consideration of the amount of functional light provided, the energy consumed, as well as the aesthetic impact supplied by the lighting system. Some buildings, like surgical centers and sports facilities, are primarily concerned with providing the appropriate amount of light for the associated task. Some buildings, like warehouses and office buildings, are primarily concerned with saving money through the energy efficiency of the lighting system. Other buildings, like casinos and theatres, are primarily concerned with enhancing the appearance and emotional impact of architecture through lighting systems. Therefore, it is important that the sciences of light production and luminaire photometrics are balanced with the artistic application of light as a medium in our built environment. These electrical lighting systems should also consider the impacts of, and ideally be integrated with, daylighting systems. Factors involved in lighting design are essentially the same as those discussed above in energy conservation analysis.
Architectural lighting design focuses on three fundamental aspects of the illumination of buildings or spaces. The first is the aesthetic appeal of a building, an aspect particularly important in the illumination of retail environments. Secondly, the ergonomic aspect: the measure of how much of a function the lighting plays. Thirdly is the energy efficiency issue to assure that light is not wasted by over-illumination, either by illuminating vacant spaces unnecessarily or by providing more light than needed for the aesthetics or the task.
Each of these three aspects is looked at in considerable detail when the lighting designer is at work. In aesthetic appeal, the lighting designer attempts to raise the general attractiveness of the design, measure whether it should be subtly blended into the background or whether it should stand out, and assess what kind of emotions the lighting should evoke. The functional aspects of the project can encompass the need for the project to be visible (by night mostly, but also by day), the impact of daylight on the project and safety issues (glare, colour confusion etc.).
For simple installations, hand-calculations based on tabular data can be used to provide an acceptable lighting design. More critical or optimized designs now routinely use mathematical modeling on a computer.
Based on the positions and mounting heights of the fixtures, and their photometric characteristics, the proposed lighting layout can be checked for uniformity and quantity of illumination. For larger projects or those with irregular floor plans, lighting design software can be used. Each fixture has its location entered, and the reflectance of walls, ceiling, and floors can be entered. The computer program will then produce a set of contour charts overlaid on the project floor plan, showing the light level to be expected at the working height. More advanced programs can include the effect of light from windows or skylights, allowing further optimization of the operating cost of the lighting installation. The amount of daylight received in an internal space can typically be analized by undertaking a daylight factor calculation.
The Zonal Cavity Method is used as a basis for both hand, tabulated, and computer calculations. This method uses the reflectance coefficients of room surfaces to model the contribution to useful illumination at the working level of the room due to light reflected from the walls and the ceiling. Simplified photometric values are usually given by fixture manufacturers for use in this method.
Computer modeling of outdoor flood lighting usually proceeds directly from photometric data. The total lighting power of a lamp is divided into small solid angular regions. Each region is extended to the surface which is to be lit and the area calculated, giving the light power per unit of area. Where multiple lamps are used to illuminate the same area, each one's contribution is summed. Again the tabulated light levels (in lux or foot-candles) can be presented as contour lines of constant lighting value, overlaid on the project plan drawing. Hand calculations might only be required at a few points, but computer calculations allow a better estimate of the uniformity and lighting level.
Practical lighting design must take into account the gradual decrease in light levels from each lamp owing to lamp aging, lamp burnout, and dirt accumulation on fixture and lamp surfaces. Empirically-established depreciation factors are listed in lighting design handbooks.
Prior to the 1960s, the concept of illumination in architecture was not considered to be important by many architects or consulting engineers. This changed with the formation of the International Association of Lighting Designers (IALD) in 1969, the current mission of which is "to serve the IALD worldwide membership by promoting the visible success of its members in practicing lighting design." This created a new attitude towards the profession and raised the profile of architectural lighting design, one of the principal goals of the organization.
The European Lighting Designers' Association (ELDA, later ELDA+) was formed in 1993; in 2007, ELDA changed its name to the Professional Lighting Designers Association (PLDA). These two organizations are the main authorities regarding lighting design in architecture.
The Illuminating Engineering Society of North America (IESNA) seeks to improve the lighted environment by bringing together those with lighting knowledge and by translating that knowledge into actions that benefit the public.
The International Commission on Illumination (CIE) is an organization "devoted to international cooperation and exchange of information among its member countries on all matters relating to the science and art of lighting." CIE works globally to develop and publish lighting design standardization and best-practice documents.
The Professional Lighting & Sound Association (PLASA) represents the interests of many lighting designers and manufacturers, several of which are involved in the Architectural lighting market. PLASA is UK orientated, but does represent companies on a European and International level.
There are many more nationally-based organizations such as the Schweizerische Licht Gesellschaft (SLG) in Switzerland, the Association de Concepteurs Eclairage (ACE) in France, the Hellenic Illumination Committee (HIC) in Greece and the Associazione Professionisti dell'Illuminazione (APIL) in Italy.
With the increase in global focus on green design and energy codes, lighting design and its role in sustainability have become more well known, resulting in a number of lighting-specific trade publications and an increase in coverage in architectural publications.
The following are publications specific to lighting design, covering the global-nature of the industry: