How to choose the appropriate luminous flux according to the illumination standards of different spaces

Illuminance is an important indicator of lighting levels, measured in lux. It is defined as the luminous flux received per unit area. Luminous flux, measured in lumens (lm), represents the total amount of visible light emitted by a light source per unit time. In lighting design, it's important to first determine the target illumination standard based on the space's intended use. Then, based on the space's area, calculate the required total luminous flux to select appropriate LED fixtures.

Common Illumination Standards for Indoor Lighting

Different indoor spaces have different contrast requirements. According to GB 50034, the "Architectural Lighting Design Standard," and the IES International Lighting Design Guidelines, common standards are as follows:

Office workspaces: 300-500 lx

Classrooms, general teaching areas: 300 lx

Classrooms, laboratories, and drawing rooms: 500 lx

Hospital wards: 100-200 lx

Hospital operating rooms: 1000 lx or higher

Shopping malls: 300-500 lx

Supermarket checkout counters: 500 lx

Restaurant dining areas: 150-300 lx

Living rooms: 100-200 lx

Study rooms: 300-500 lx

These illumination standards provide designers with a clear basis.

Luminous Flux Calculation Method

After determining the target illuminance, the required total luminous flux can be calculated using the formula:
Φ = E × A ÷ UF ÷ MF
Where Φ is the total luminous flux, E is the design illuminance, A is the area of the space, UF is the utilization factor, and MF is the maintenance factor. The utilization factor reflects the effects of the lamp's light distribution and room reflectivity and is typically set between 0.5 and 0.7. The maintenance factor accounts for lamp dust accumulation and lumen degradation and is typically set around 0.8. This formula can be used to determine the total luminous flux required for the space. The number and wattage of luminaires can then be determined based on the luminous flux of each luminaire.

Luminous Flux Selection for Office Spaces

Office spaces require comfortable and uniform lighting. For example, a 100-square-meter open office area has a target illuminance of 500 lx. Assuming a utilization factor of 0.6 and a maintenance factor of 0.8, the total luminous flux requirement is:
Φ = 500 × 100 ÷ 0.6 ÷ 0.8 ≈ 104,000 lumens
If LED panel lights with a luminous flux of 4,000 lumens per light are selected, approximately 26 units are required to meet the standard. This calculation method ensures that workspaces meet illumination standards and avoids under- or over-illumination.

Luminous Flux Selection for Commercial Spaces

Shopping malls and retail stores require lighting to highlight merchandise and create a comfortable shopping atmosphere. The typical illumination standard for retail stores is 300 to 500 lux, with key areas such as checkout counters and display shelves requiring higher brightness. Taking a 200-square-meter retail space as an example, with a target illuminance of 400 lx, a utilization factor of 0.6, and a maintenance factor of 0.8, the total luminous flux requirement is:
Φ = 400 × 200 ÷ 0.6 ÷ 0.8 ≈ 167,000 lm

The design can combine LED downlights, spotlights, and panel lights of varying wattages to provide uniform illumination and accent lighting in different zones, meeting functional and visual requirements.

Luminous Flux Selection for Medical Spaces

Medical spaces have even higher lighting requirements. Patient wards typically require 100-200 lx for comfortable patient rest. Taking a 50-square-meter ward as an example, with a target illumination of 150 lx, a utilization factor of 0.6, and a maintenance factor of 0.8, the total luminous flux requirement is:
Φ = 150 × 50 ÷ 0.6 ÷ 0.8 ≈ 15,625 lm
If LED ceiling lamps with a luminous flux of 2500 lm each are used, approximately seven lamps are sufficient. Operating rooms require a high illumination of over 1000 lx, typically using high-efficiency shadowless lamps to ensure precision and safety during surgical procedures.

Luminous Flux Selection for Home Spaces

Home environments emphasize comfort and ambiance. Living rooms typically require 100-200 lx, bedrooms approximately 75-150 lx, and studies 300-500 lx. Taking a 20-square-meter study as an example, with a target illuminance of 400 lx, a utilization factor of 0.6, and a maintenance factor of 0.8, the total luminous flux requirement is:
Φ = 400 × 20 ÷ 0.6 ÷ 0.8 ≈ 16,667 lm
By arranging desk lamps, ceiling lamps, and auxiliary lighting, we can ensure both high local illuminance and a uniform lighting environment throughout the space.

Human Factors in Luminous Flux Selection

In addition to standards and formulas, human factors in lighting must also be considered. Color temperature and color rendering index significantly influence spatial ambiance and visual comfort. Offices typically choose neutral white light around 4000K, while retail and restaurant spaces tend to use warm white light at 3000K. Medical spaces tend to favor cool white light at 5000K. A high color rendering index (CRI ≥ 80, with some spaces requiring CRI ≥ 90) ensures color reproduction and enhances the quality of the space.