Modern architecture and design projects continue to deem energy reduction a top priority, and LED lighting is one of the core elements used to accomplish this goal.

The market for halogen and incandescent light bulbs has dimmed, with LED lighting taking their place due to its energy efficient nature.

Thel movement has been recognised by environmental groups, industry members and even governments, many of which are now implementing policies to formalise the use of LED lighting.

Kevin Dinh, partner at Light-Box Studio

When considering its application in a commercial setting, it is crucial that LED lighting design contributes both practically and environmentally.

In offices, lighting is required to support productivity, be kind to human eyes and be automated for flexible working hours. In a retail environment, lighting is used to highlight point of sale items and encourage customers in store, while hotel use lighting to create guest room ambiance.

Before architects and designers instantly seek LED lighting for their next project, however, there are plenty of benefits and limitations they may not be aware of.

Kevin Dinh, partner at Light Box Studio in Melbourne, a boutique lighting design firm providing architectural lighting design review and assessment, has worked with his team on an array of projects, including the lighting design of 41X, the new Australian Institute of Architects Building in Melbourne.

Lighting design at AIA 41X building

In recent years, Dinh has noticed a steady increase in clients requesting LED lighting, saying the technological improvements to LED have been “tremendous.” He attributes the appeal of LED lighting to its flexibility – it can be used indoors and out – along with its “efficiency and effectiveness” compared to other lighting sources.

“We have also seen many manufacturers focussing a large portion of their research and development on LED technology and luminaire development with some even phasing out other light sources all together,” he said.

Despite LED lighting’s growing popularity, Dinh noted several technical parameters that designers and users should be aware of before making their lighting decision.

Luminous efficacy

Luminous Efficacy – how well a light source produces visible light

“Luminous efficacy indicates how efficiently a light source can produce visible light,” he said. “Currently, white LED can produce up to 130 lumens per watt which outshines the linear fluorescent technology at around 100 lumens per watt and certainly is a big improvement from the once popular halogen light source at around 20 lumens per watt.”

“LED efficacy continues to improve substantially. We can either have the same LED lumen package for less energy consumption or have the same energy consumption with much more light generated from the newer chips.”

Colour Rendering Index (CRI)

Colour Rendering Index

CRI denotes the ability or a light source to reveal the colour of an object it is illuminating. The maximum CRI value is 100.

“This is particularly important in applications where colour matching is required (e.g. dental labs, paint shops, etc.) or merchandise display (e.g. retail shops),” Dinh said. “CRI80+ for LED has become the norm in the industry while CRI90+ has become readily available and CRI100 is not far behind.”

Thermal Management

Designers need to consider optical control and glare reduction

Dinh says heat is LED lighting’s biggest limitation.

“Overheating is one of the main reasons for light output reduction and premature failure. This generally happens when the ambient temperature exceeds the manufacturer’s recommendation of +40 to +55. Better thermal management means improved lamp life and luminous efficacy, which is the main focus of many researches,” Dinh said.

A 2014 study on the Effect of LED lighting on the cooling and heating loads in office buildings found that while LED lighting has the potential to provide energy savings, 75 to 85 per cent of the light electric power in LED lights is still generated at heat levels which could in turn have a negative effect on the cooling load.

Glare

Glare is another issue Dinh has come across.

The small-scale design of LED chips allows them to fit into an array of lights, offering flexible application. There is, however, a drawback.

“With so much visible light produced from a small surface area, they can produce obtrusive glare,” Dinh said. “Optical control and glare reduction are important considerations. We find that concealed LEDs rather than LEDs close to the surface tend to address this issue.”

Colour control

Colour control is a limitation to LED lighting

“Another issue with LED technology is colour control and colour variations in the light output, especially in white LEDs,” said Dinh. “White LEDs generally comprise blue LEDs and a yellow phosphor coating. The colour output depends largely on the phosphor components.”

Dinh referred to MacAdam Ellipses – an industry term used to describe colour variations in terms of perception of LEDs produced by the same manufacturer.

“Some manufacturers choose to follow an international standard of seven step MacAdam at +/- 3500 Kelvin. However, there are manufacturers who don’t recognise this standard,” he said. “It’s important to note that the higher MacAdam step, the greater the variance in LEDs’ light output colour from one to another, making a constant colour surface. Some higher quality LEDs are manufactured to 2-3 step MacAdam, which means a more consistent in colour appearance to the naked eye.”

Cost

The Indigo Hotel in Shanghai demonstrates LED lighting design

While LED lighting can offer savings of up to 80 per cent on energy costs and require less maintenance, their replacement costs remain a significant limitation. LEDs cost more to replace compared to other light sources and in some cases, an entire luminaire (LED lamp and housing) needs to be replaced once the LED has reached its end of life or failed.”

“In certain applications, once examined over a long period of time, say 100,000 hours, taking into account capital costs, lamp replacement costs and energy consumption savings, an LED light source still struggles to be more cost effective than other light sources,” Dinh said.

All things considered, LED lighting remains a developing technology, though Dinh predicts it will continue to dominate the lighting market, particularly once some of its limitations are addressed.

“We will see the energy efficiency improves further with even higher efficacy, increased CRI and better thermal control,” he said. “With mass productions and the competitive market, the price will be even more affordable which will see a further growth in applications and projects. We have seen an increase in LED panels with opal diffuser on the market to combat the glare issue, making them a considerable option for office lighting. These panels’ prices have dropped significantly to be almost on par with the traditional linear fluorescent option. This might be the next trend in office lighting.”