Lighting design plays a key role in commercial buildings which are typically used by people to perform a task or conduct an activity. To achieve their tasks or activities in a workspace, the right amount of illuminance is necessary, over-lighting is as much as a hindrance to accomplishing tasks as under-lighting. Commercial lighting compared to industrial or residential lighting involves higher initial costs, higher maintenance, longer durability and lifespan and higher service costs. To identify the illumination level requirements or lux level requirements of a commercial building, it would be useful to understand the units of measurement of illuminance, the intensity or amount of light and the efficacy of the relationship between lux and lumen.
Illuminance or lux is the intensity of the level of light and ‘luminous flux’ or lumen is the amount of light produced. Lux is the unit of measurement usually measured in foot candles, one lumen is the measurement of the intensity of the light output and is equal to one lux across an area of one square meter. Given an area you may need to illuminate, the measurement of lux helps you identify the output or lumen required. Typically, for an office which is brightly lit around 400 lux of illumination is required and an office space which uses 100W incandescent bulbs in ceiling panels would produce 1600 lumens as the output of light. When a lighting design company designs light fixtures for a large commercial area, the number of light fixtures is usually increased to get higher lumen keeping in mind the lux level requirements.
A primary factor in ensuring efficiency in light design is achieved by balancing lux and watts or managing the amount of power used to produce light. The measurement of energy efficiency or the power required for light fixtures (luminaires) to operate is known as watts or wattage. The rate at which a light fixture converts power to light or watts to lumen is known as luminous efficacy and measured in lumens per watt (LPW). Typically, an office or commercial space with ceiling panels which would use 32W T5 or T8 fluorescent lamps would usually produce 50 lumens/watt.
Lux level requirements are calculated to determine the appropriate number of lights, the type of light fixtures and the best possible commercial lighting solution, based on the size of the office or commercial space, the type of task or activity which will be conducted and the energy efficiency standards required.
In most cases, based on the client requirements of lux levels, office spaces are over-lit and are usually more than rates mentioned in the lighting standard codes and guidelines developed by professional lighting bodies. Lighting consultants and MEP engineering design teams while keeping in mind client requirements must also consider lighting codes and guidelines which mention the minimum lux level requirements that need to be maintained. Several lighting professional bodies have published handbooks and guidelines, some of which include lighting guides published by the Chartered Institution of Building Services Engineers (CIBSE) in the UK, the IESNA Lighting Handbook by the Illuminating Engineering Society of North America and guides and lighting codes provided by the Lighting Council Australia.
To improve energy efficiency and reduce consumption, several countries have presented lighting codes and green building solutions which have made lighting manufacturers develop higher energy efficient light fittings. For offices and commercial spaces, the stipulated lighting watts/m2 is considered to be within the range of 10 to 15 watts/m2. With the increase in the use of LED light fixtures, lighting consultants are required to maintain lighting watts within the range of 5 to 8 watts/m2, while maintaining lux level requirements.
To ensure commercial lighting designs provide higher energy efficiency, lower energy consumption and better control on energy usage, lighting consultants and MEP engineering design teams must consider trending lighting solutions in the industry. From LED fixtures with advanced lighting controls, energy harvesting technologies, interactive lighting to connected lighting, there are several trends which a lighting design company could use to provide high energy-efficiency and customer-centricity in lighting design solutions for commercial spaces.