The lumen method is a procedure used to ascertain the relationship between several aspects of lighting, including the number and types of lamps and luminaires, the characteristics of the room, and the average level of illuminance on the work plane. It provides a standardized approach to ensure optimal lighting conditions.
The procedure starts by determining the total luminous flux required to achieve the desired illuminance level on the work plane. This flux is usually measured in lumens (hence the name "lumen method"). The required illuminance level is based on specific standards or guidelines for different applications, such as offices, schools, or industrial spaces.
Next, the flux is distributed over the work plane by considering both direct and reflected flux. Direct flux refers to light emitted directly from the lamps or luminaires, while reflected flux takes into account light bounced off surfaces, contributing to the overall illuminance. Proper calculation of this distribution is vital to achieving a uniform lighting environment.
Room Characteristics
To accurately apply the lumen method, it is essential to consider the characteristics of the room where lighting is required. Factors such as room size, shape, wall colors, ceiling height, and the presence of light-absorbing or light-reflecting surfaces impact the distribution of light.
These characteristics affect the coefficients used in the lumen method calculations. For instance, the coefficient to account for reflectance is higher in rooms with predominantly light-reflecting surfaces, while it is lower in rooms with darker or more light-absorbing surfaces. The lumen method's ability to adapt to various room characteristics allows for customized lighting solutions.
Applying the Lumen Method
The lumen method considers lamps and luminaires as both point sources and line sources of light. Point sources, such as incandescent bulbs, emit light uniformly in all directions. Line sources, on the other hand, distribute light mainly in one direction and are commonly found in fluorescent or LED luminaires. The combination of various point and line sources enables designers to achieve the desired illuminance levels.
Furthermore, the lumen method supports the concept of light loss factors, which considers factors that reduce the actual illuminance from the planned values. These factors could include dust accumulation, lamp depreciation, and dirt on luminaires. By incorporating light loss factors, the lumen method ensures that the lighting system remains effective over time.
The lumen method, or flux method, is an essential procedure in lighting design, allowing designers to determine the appropriate number and types of lamps and luminaires based on desired illuminance levels. By considering room characteristics, direct and reflected flux, and the concept of light loss factors, the lumen method provides a reliable framework for achieving effective and efficient lighting solutions. Applying this method can help create visually comfortable environments while optimizing energy consumption.