Warehouse Daylighting Calculator: How Much Skylight Area Do You Need?

Variable 1: Target Lux Level at Floor

BIS IS 3646 specifies minimum lux levels for different industrial activities:

• General storage and bulk warehousing: 100 to 150 lux minimum
• Active picking, packing, and dispatch operations: 150 to 300 lux
• Quality inspection and detailed assembly: 300 to 500 lux
• Fine inspection, colour matching, precision work: 500 to 750 lux

For most Indian logistics warehouses and distribution centres, the target is 150 to 200 lux. This is the outcome you are engineering toward every other variable works backward from this number.

Variable 2: Available Daylight – Design Sky Illuminance

India’s daylight availability varies significantly by climate zone:

• High irradiance zones (Rajasthan, Gujarat, Madhya Pradesh): 20,000 to 25,000 lux on a typical working day
• Moderate irradiance zones (Maharashtra, Karnataka, Andhra Pradesh): 15,000 to 20,000 lux
• Lower irradiance zones (Northeast, coastal Kerala, parts of West Bengal): 10,000 to 15,000 lux during monsoon months

Variable 3: Roof Height and Light Distribution

Roof height determines how widely light spreads from each skylight panel to the floor below:

• Roof height 4 to 6 metres: Each square metre of panel illuminates approximately 8 to 12 square metres of floor area
• Roof height 8 to 10 metres: Each square metre illuminates approximately 12 to 18 square metres of floor
• Roof height 12 metres and above: Each square metre illuminates 18 to 25 square metres of floor

High-bay warehouses require proportionally less skylight area per square foot of floor than low-bay storage one of the key reasons generic percentage rules are unreliable.

Variable 4: Skylight Panel Transmission Efficiency

The visible light transmission (VLT) of a skylight panel directly affects how much skylight area is needed. Standard polycarbonate sheets start at 70% to 85% VLT but degrade to 40% to 60% within five to eight years through UV yellowing and hazing – reducing daylight delivery progressively over time. Brilantor daylighting panels are designed and tested for consistent VLT performance for 20+ years without yellowing or hazing, with multi-layer diffusion construction providing more even light distribution than single-layer transparent sheets.

Variable 5: Obstructions and Shading

Several categories of obstruction reduce effective illumination at floor level:

• Racking systems – high-bay racking creates shadow zones in picking aisles; a design ignoring racking layout fails precisely where most activity occurs
• Structural steelwork – purlins and cross-bracing cast shadows and may obstruct optimal panel placement
• Mezzanine floors any horizontal structure between roof and floor intercepts light distribution; SkyPipe tubular skylights address these areas
• External shading – adjacent buildings or structures shading the roof during certain times of day reduce effective available daylight

Variable 6: Uniformity Requirements

The uniformity ratio minimum to average lux across the floor – should be 0.7 or above for most warehousing operations. Achieving this requires specific panel spacing relative to roof height, calculated from the panel’s light distribution angle. Brilantor’s diffusion technology maximises the distribution angle, reducing panel density needed to achieve uniform coverage and improving the lux uniformity ratio at floor level.

Variable 7: Operational Hours and Shift Pattern

A single-shift warehouse operating 7am to 6pm gets maximum benefit from daylighting every operational hour falls within daylight availability. A double-shift warehouse operating 6am to 10pm loses daylighting benefit for the evening shift. The shift pattern affects the ROI calculation but does not change the skylight area required to achieve the target lux level during daylight hours.