The lumen method is a commonly used lighting design method that takes into account the illumination requirements of a space, as well as the characteristics of the lighting fixtures being used. The method is based on the principle of conservation of energy, and is used to determine the number of fixtures required to achieve a desired level of illumination in a given space.
Here are the basic steps involved in using the lumen method for lighting design:
- Determine the illumination requirements: The first step in the lumen method is to determine the required level of illumination for the space being lit. This can be done by referring to lighting standards or guidelines, such as those provided by the Illuminating Engineering Society (IES).
- Calculate the lumens required: Once the required level of illumination has been determined, the next step is to calculate the total number of lumens required to achieve that level of illumination. This is done by multiplying the area of the space by the required illuminance in lux.
- Determine the fixture efficiency: The next step is to determine the efficiency of the lighting fixtures being used. This is typically expressed as a percentage, and takes into account factors such as the reflectance of the walls and ceiling, the efficiency of the lamps being used, and any losses due to the fixture design.
- Calculate the total number of fixtures: Once the lumens required and fixture efficiency have been determined, the total number of fixtures required to achieve the desired level of illumination can be calculated. This is done by dividing the total lumens required by the product of the fixture efficiency and the lumen output of the fixtures being used.
- Verify the design: Finally, the lighting design should be verified to ensure that it meets the required illumination levels and provides a visually comfortable environment. This may involve making adjustments to the design or selecting different fixtures as needed.
This method gives rough and reasonable estimates of the lamps / luminaires needed. It is used in areas where a uniform light intensity is required for the work area. Illumination level required at the work surface is obtained by,
E = illumination level required at the work surface
A = total area of the plane where the work is done.
Φrec = flux of light received on the working surface.
To estimate the average illuminance of the installation at a particular stage in its life. This is achieved by using the following formula:
Em = Maintained illuminance (lux)
ϕin = Initial luminous flux of the light source (lumen)
n = Number of lamps per luminaire
N = Number of luminaires
A = Area to be illuminated (m2)
UF = Utilization factor for the luminaire in the room
MF = Maintenance factor
The lumen method is a straightforward and widely used lighting design method that can help ensure that a space is adequately lit while minimizing energy consumption and reducing costs.
Classification of lighting system
Illumination in architecture – home page
FD Architect Community Forum Discussion
- Illumination – introduction
- Basic Terminology and Definitions
- Laws of Illumination The Inverse Square Law of Illuminance Illuminance (E) at any poi
- Laws of Reflection and Refraction
- Visual efficiency & comfort
- Day lighting
- Components of Daylight Factor
- Artificial Lighting Design
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