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Arjun Rathi, founder and principal architect, Arjun Rathi Design, on critical aspects of lighting design

Arjun Rathi, founder and principal architect, Arjun Rathi Design, on critical aspects of lighting design

Lighting design, Column, Arjun Rathi, Founder and principal architect, Arjun Rathi Design, Daylight, Lighting, Illumination, Artificial lighting, Lumens

“A truly great structure, one that is meant to stand the tests of time never disregards its environment. A serious architect takes that into account. He knows that if he wants presence, he must consult with nature. He must be captivated by the light. Always the light. Always.”
– Quote from The Lake House (2006)

Architects and lighting designers have long understood the power of light and its ability to define, highlight and transform architecture. Lighting automation through its discipline, allows automated changes in lighting levels to affect mood, emphasise architecture, illuminate art and influence action. It has become one of the most important elements for all categories of projects, more so, for offices where people tend to spend almost a third of their day.

Mixing natural daylight and artificial lighting has become the norm now. Most residential owners  insist on the inclusion of natural light at home to bring a certain cheer or charm to spaces but it has become equally important for commercial projects. A carefully laid out lighting design must use sunlight to illuminate at least 25 to 30% of the floor areas, which can lead to significantly lower monthly energy consumption.

Distinguish illumination from lighting
Lighting and illumination are not the same and so, they should be approached differently. Light is measured in lumens, while illumination is in lux. Lumens refers to the amount of light coming from a source, while lux measures the intensity. Lux is equal to an illumination level of one lumen per sqm. When designing lighting, it is important to carefully differentiate these two instead of combining them. Each space reacts differently to varying lumens and lux requirements. For example, general lighting in commercial areas needs at least a minimum of 500 lux. Car parks and roadways need only 20-30 lux, while washrooms, foyers, dining rooms need around 200 lux.

Consider daylight
Poorly planned artificial lighting systems bring huge cost setbacks. The right amount of daylighting entering the building can greatly reduce capital and running costs. Which is why daylight factor is commonly used to determine the ratio of internal to external light levels. It’s important to benchmark daylight before determining the type of artificial lighting a project needs, especially for a tropical environment like India, where the available sunlight can be quite overwhelming and thermally discomforting when not managed correctly.

Identify artificial lighting intentions
Intentions fall into three major categories: task lighting, ambience lighting, and accent lighting. Task lighting refers to general lighting for work concentration or functional activities that normally make use of widespread white light such as in office or preparatory kitchens. Ambience lighting plays more with moods and may have a softer glow to a place for lounging or relaxation and would typically take advantage of indirect warm whites or yellow lights. Accent lights bring interest to a certain architectural or interior feature by casting light and shadow drama using focused light as a means to highlight artistic expressions such as on paintings or sculptural pieces. Organising lighting intentions can help visualise fixture placements, interior layout and make better decisions on lighting locations.

In terms of lumens rather than watt
Prior to LED technology, the brilliance of a light fixture was dependent on the amount of power it consumes. Hence, watt was the unit used to measure the electrical power a device consumed as a connotation to the amount of light it delivers. But LEDs use less power compared to their output of illuminance. Therefore, it is best to think in terms of lumens rather than watts when considering lighting strategies.

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