Last edited 19 Nov 2020

Lighting in commercial buildings

AR114 - Lighting Considerations for Optimum Productivity in Commercial Buildings.jpg


[edit] Introduction

What makes commercial buildings productive? Well, in essence, they should have an environment, system or workflow that encourages occupants to perform their tasks to the best of their ability. Commercial buildings may consist of offices, retail establishments, institutions, hospitals, etc. Pleasant working conditions can be created in such buildings in a number of ways, with effective lighting being a significant contributor.

The right lighting can enable optimum functioning, satisfaction and a ‘task-centric’ atmosphere. Commercial lighting may be expensive initially, but it is designed to be longer lasting, more durable and have better energy saving potential than lighting for some other settings. It is important that mechanical and electrical design consultants or engineers collaborate with lighting experts to determine the right combination of lighting for commercial spaces.

Essentially, lighting designs should cater to the type of indoor activity in the commercial building such that the lux levels and energy sufficiency standards are created and maintained. Lighting designs should consider the illuminance of the internal spaces, the function to be performed and appropriate light fixtures.

Light has a considerable influence on both our bodies and minds. The right quantities of daylight and artificial light can positively affect our health. Sufficient daylight and artificial light in an office space can improve satisfaction and efficiency, through a creative, dynamic and motivating environment. Appropriate light can inspire, improve communication, set a mood and influence emotions. Spaces can be made desirable, resulting in a general sense of well-being.

Over-lighting can be just as detrimental as under-lighting in commercial spaces. People should have enough light to perform and complete their tasks but not so much that it becomes blinding. Tasks that require a high degree of detailing, such as drafting, requires more light than one that involves walking. The IESNA Lighting Handbook, published by the Illuminating Engineering Society, is a popular reference source for lighting design.

Designers must understand illuminance, or the amount of light that hits a surface. For example, in an office, it is relevant to know the illuminance on a desk. The unit of measuring illuminance is a foot candle (FC) or lux, and 1 FC is the amount of light on 1 square foot of any surface using 1 lumen of light from 1 foot away from the surface – 1 lumen per square foot. Similarly, 1 lux is the amount of light on 1 square metre of any surface using 1 lumen of light from 1 metre away from the surface – 1 lumen per square metre. Also, 10 lux is approximately 1 FC. An illuminance of 400 lux would be sufficient for a well-lit office.

Another factor to consider is lighting power density, or LPD, which is the amount of power used by lighting per unit of building area. For instance, in the United States, LPD is measured in watts per square foot, whereas this may differ from country to country and is dependent on local and international codes. The watt measurement includes power used by lighting fixtures, ballasts, controls, transformers or any other device or component involved in lighting. Calculations for LPD may be performed using the Building Area Method or the Space-by-Space method, which has been shown to be more accurate and enable a lower LPD estimate.

The IESNA Lighting Handbook recommends light levels for most conceivable spaces. A few of them that are relevant to commercial buildings can be found below:

Room Type Light Level (FC) Light Level (Lux) IECC 2015 LPD (Watts Per Sf)
Cafeteria 20-30 FC 200-300 lux 0.65
Conference Room 30-50 FC 30-50 FC 1.23
Exhibit Space 30-50 FC 300-500 lux 1.45
Kitchen/Pantry 30-75 FC 300-750 lux 1.21
Lobby/Office 20-30 FC 200-300 lux 0.90
Lounge/Breakroom 10-30 FC 100-300 lux 0.73
Mech/Elec Room 20-50 FC 200-500 lux 0.95
Office-Open 30-50 FC 300-500 lux 0.98
Office-Private 30-50 FC 300-500 lux 1.11
Parking-Interior 5-10 FC 50-100 lux 0.19
Restroom/Toilet 10-30 FC 100-300 lux 0.98
Retail Sales 20-50 FC 200-500 lux 1.59
Stairway 5-10 FC 50-100 lux 0.69
Storage Room 5-20 FC 50-200 lux 0.63
Workshop 30-75 FC 300-750 lux 1.59

[edit] Types of light fixtures

T5, compact fluorescent lights and LED light fixtures are commonly used in commercial buildings:

[edit] Lux levels

In large areas, to achieve a higher lumen, the number of light fixtures is increased. The lux level required is calculated based on the size of the space, the activity that takes place there and the required energy efficiency. Software tools, such as DIALux or AGi32, can be used for lux level calculations.

Guidelines and local codes determine the minimum lux levels required in different environments. Consultants should ideally employ new advances in the lighting industry to help reduce energy usage and improve comfort, such as connected lighting, LED fixtures with advanced controls and interactive lighting. Daylight, LED light and harvesting technologies must be balanced.

Lighting in offices, besides being at optimum levels to help perform and complete tasks, must also meet the biological lighting needs of office personnel in the future. Here’s how it could be possible to help employees stay healthy and alert:

  • A combination of direct, indirect and vertically lit surfaces have been found to be pleasing for most employees. When the desk light can be individually controlled, greater motivation and accuracy in tasks has been noticed. Designers should try to avoid designing lighting that only has downward-directed illumination.
  • Light intake influences sleep and a feeling of wellness, resulting in higher productivity. Natural light helps people tell the time of day. When there is a lack of natural light, the body’s circadian rhythm loses its pace, and as a result, people become tired and listless. A mix of different lighting options can reduce this effect.
  • Spaces can feel smaller due to insufficient light. A person’s work area should ideally enjoy a minimum of 3 percent of daylight. This ensures that people are emotionally upbeat, and an outside view is an added bonus.
  • Preventing SAD (seasonal affective disorder) – During a season that causes people to experience less light intake, a type of depression linked to lack of light (SAD) can result. Moodiness and listlessness are symptoms. Sufficient amounts of bright light can help treat and prevent this disorder. An illumination level of 2000 lux at work in the morning and afternoon reduces physical reactions to stress and energises the body.
  • Changing light to suit the time of day – When people need to work throughout the night or a good part of the night, light intensities should be increased and so should the quantity of bluish white light in the room. When tasks are almost complete and people are winding down for the day, the light setting should be warm and of low intensity to encourage a calming effect.
  • Installation of applications to negate the blue light effect – Sometimes, there is difficulty in falling asleep after a long day in front of the screen. This is because of the high blue light content of backlit screens, which at night upsets the circadian rhythm and can affect one’s health. Applications, such as F.lux. or Twilight, can reduce the blue light on Android phones. Other applications can relate a screen’s colour and brightness to that location’s daylight. It can be beneficial to have warm light sources combining with indirect and general light with varying colour temperatures near the working space.

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