“We wanted to make sure his staff could see clearly and with comfort,” Seshadri says. “This affects safety and means fewer rejects and accidents.”
With 45 years of teaching and hands-on experience in the professional lighting field, Sesh, as he is better known in Singapore, says some clients have got it all wrong when it comes to light retrofitting.
“When considering lighting in the office, there are five factors to look at,” Seshadri says. “Besides energy cost, there are other considerations just as important – comfort of the staff, image of the company, the ambience of the working environment and performance of the staff.”
The retired vice-president of Philips Lighting Asia Pacific explains: “If the environment is not conducive enough for the staff to work in, you will eventually pay more for poor performance. They get sick, they go on medical leave, they make more mistakes or create re-work, and you have to take all that into consideration as well.”
Light retrofitting must therefore comply with certain standards. Most countries follow the lighting levels recommended by the ISO 8995-1: 2003, but as a standard guide, 500 lux is good enough, in Seshadri’s view, for practically every kind of office work. “In the case of highly complex technical drawings, the recommended level is higher, at 750 lux, but generally, most people are comfortable with 500 lux,” he says.
Lighting requirements for types of interior workspaces
Source: Gritti Consulting
Lighting needs vary depending on age. Seshadri elaborates: “For example, a 12-year-old child can see and work for some hours at 200 lux, but a 40-year-old will need 600 lux while a 60-year-old will need 3,000 lux because of the gradual and natural degradation of the human eye. That’s what makes retrofitting very challenging because every workplace has a diverse mix of young and older people.
“However, the wonderful thing about the human eye is that it is able to cope with illuminance of as high as 100,000 lux when one is walking in the open and 10,000 lux under the shade of a tree. Compared to nature’s lighting levels to which human are used to for millions of years, 500 lux is a mere half-a-percent and hence should not be compromised.”
Given that the recommended office lighting level is 500 lux, the calculations work out to be only 10 watts per sq m. So for an average space of 8 sq m for typical office staff, the energy consumption is estimated at 80
watt hours or 0.80 kWh.
“At the tariff of 40 sen per kWh, the cost of energy consumed to light up a workplace at 500 lux for ten hours is only 32 sen. It is much cheaper than a cup of coffee,” he quips.
Seshadri wears many hats. He chairs the IEC Technical Committee 34 (lamps and related equipment) for SPRING (Singapore Standards) and is secretary-general of the Lighting Association of Singapore (LAS), which represents the CIE (International Commission on Illumination). He also lectures part-time at the School of Design and Environment at the National University of Singapore and the Building and Construction Authority (BCA) Academy.
While in Kuala Lumpur early this year to speak at the Institute Sultan Iskandar Seminar on Retrofitting Buildings for Energy Efficiency, Seshadri provided delegates with a broad overview of the lighting industry. Starting with the incandescent light bulb, Seshadri went on to trace other types of lighting equipment right up to light-emitting diodes (LEDs), which he says may become the most dominant light source within the next ten years.
Until the prices of LEDs drop further, however, the straightforward retrofitting approach is to replace incandescent lamps with compact fluorescent lamp (CFL) tubes, while the magnetic ballasts are best replaced with electronic ballasts.
“These are two immediate simple steps to save on energy,” Seshadri says. “Generally, CFLs consume only one-fifth of the energy used by an incandescent light bulb.”
Source: Gritti Consulting
He also highlights the environmental benefits of switching to CFLs: “If you replace a 100 W incandescent light bulb with a CFL of 20 W and light it for 1,000 hours in a year, you are saving a total of 80 kWh. This translates to 33.6 tonnes of reduction in carbon dioxide emissions for a million households using just one CFL each!” he says.
Another pointer for retrofitters is to look into using electronic ballasts instead of magnetic ballasts, which consume more power.
For example, for a TLD 36 W (fluorescent tube), there is a magnetic ballast loss of 9W compared to 4 W ballast loss for an electronic ballast.
“This means that in a scenario with two lamps, 90 W is the input for the electromagnetic ballast circuit compared to only 72 W for electronic ballasts. At the current tariff, in a year where the lights are turned on for 4,000 hours, the energy saved is 72 kWh, which translates into RM28.80 (US$9.40) for the two tubes alone,” says Seshadri. “Never underestimate the saving from using electronic ballasts, although they may cost a bit more.”
As for LEDs, he is not sure whether the vast number of these products will stand up to their claim of 50,000 hours. He says that if one is working with well-established international brands, however, it is worth looking, for example, into replacing a 12 V 50 W halogen lamp with a 10 W MR16 lamp.
Biodata of K Seshadri
• CEO of Gritti Consulting Pte Ltd
• Is 70 years of age and has worked for some 40 years in the field of lighting
• Secretary-general of the Lighting Association of Singapore (LAS) and chairman of IEC Technical Committee 34 (lamps and related equipment) for SPRING (Singapore Standards)
• Holds an Electrical Engineering (Hons) degree from India and a Masters in Education from Sheffield University in the UK