Lux level requirements of commercial lighting
The main objective when using a commercial lighting is to accomplish a task or conduct an activity, which is why illuminance or the focus and amount of light is important. While under lighting impedes several types of activities, over lighting also poses a problem in accomplishing tasks. To understand lux or illumination level requirements for commercial spaces, it is important to understand the units of measurement of light and the efficacy of their relationship.
Lux or illuminance – Illuminance or lux is the unit of measurement of the intensity of the level of light, measured in foot candles. Typically, a brightly lit office would require around 400 lux of illumination.
Lumen or ’luminous flux’ – Lumen is the measurement of the total ‘amount’ of light. One lumen is the measurement of the output of light. Typically, a 100W incandescent bulb used for an office space with ceiling panels for lighting would produce an output of 1600 lumens.
The relationship between lux and lumen – Lux measurement helps determine the lumen (output) required given the area that is illuminated. One lux is equal to one lumen spread across one square meter. To achieve higher lumen when lighting a large area based on the lux level requirements, the number of light fixtures is usually increased.
Wattage or watts is the measurement of the power required to operate a light fixture (luminaire) or the energy efficiency of lighting. Luminous efficacy, defined as the rate at which a light fitting or light source can convert power (watts) to light (lumens), is measured in lumens per watt (LPW). Typically, a T8 fluorescent lamp or 32W T5 used for an office space with ceiling lights would produce 50 lumens/watt.
Calculation of the lux level is required to determine the number of lights needed in a commercial space according to its size, the type of activity and the energy efficiency required. Typically, software programs such as DIALux or AGi32 are used for lux level calculations.