DIALux Calculations: How to Verify Your Lighting Design

Why lighting calculations matter

Experience and intuition will get you part of the way in lighting design. But for a specification-grade project — where light levels, uniformity, and glare must meet specific criteria — only a proper lighting calculation will do.

DIALux is the industry-standard software for lighting calculations. It allows designers to build a 3D model of a space, place virtual fixtures with real photometric data, and calculate exactly how much light will reach every surface.

The alternative — guessing — leads to under-lit spaces, over-lit spaces, glare, hot spots, shadow patterns, and expensive rework after installation. Calculations done correctly prevent all of this.

What DIALux calculates

DIALux is capable of far more than just average lux levels. A comprehensive calculation can include:

• Illuminance. Light falling on surfaces (lux or footcandles). Both average and point-by-point.
• Luminance. Light reflected from surfaces (cd/m²). Important for glare assessment and perceived brightness.
• Uniformity. The ratio of minimum to average illuminance. Critical for task lighting and code compliance.
• Glare assessment. UGR (Unified Glare Rating) for interior spaces, GR (Glare Rating) for sports and exterior.
• False color analysis. Visual maps showing light distribution across surfaces.
• Daylight integration. Combining electric light with daylight from windows and skylights.
• Energy calculation. Power density (W/m²) and annual energy use.
• Renderings and visualizations. Photorealistic previews of how the space will look.

Understanding calculation results

A DIALux calculation report contains a lot of data. These are the most important numbers to look at:

Key metrics and what they mean

Understanding what the numbers mean in practice is essential for interpreting calculation results.

Illuminance: how much is enough?

Recommended light levels vary enormously by application:

• 50 lux — Corridors, circulation, storage
• 100-150 lux — Restaurants (ambient), lounges, hotel rooms (ambient)
• 200-300 lux — Lobbies, retail (ambient), general offices
• 500 lux — Desk work, classrooms, detailed retail
• 750-1000 lux — Detailed tasks, laboratories, drawing offices
• 1500+ lux — Precision manufacturing, inspection, surgical

These are working plane values. Ambient light levels in high-end interiors are often much lower than code minimums — by design. Code minimums are for task areas, not for creating atmosphere.

Uniformity: why evenness matters

A space can have the correct average lux level and still feel wrong if the light is uneven. Stripes, hot spots, and scallops from poorly placed fixtures are distracting and unprofessional.

Uniformity is expressed as the ratio of minimum to average (Uo = Emin / Eavg). Higher is better. For general office work, 0.7 is the standard. For corridors, 0.4 is acceptable. For sports lighting, the requirements vary by sport and level of play.

Glare: the silent quality killer

Most lighting problems are not about how much light — they are about glare. A space with 500 lux and high glare feels worse than a space with 300 lux and good glare control.

UGR (Unified Glare Rating) is the standard metric. It is calculated from the luminance of fixtures, the background luminance, and the size and position of the fixtures relative to the viewer.

• UGR 16 — Very low glare (demanding visual tasks)
• UGR 19 — Low glare (general office work)
• UGR 22 — Moderate glare (acceptable for general spaces)
• UGR 25+ — High glare (generally unacceptable for prolonged occupancy)

Common mistakes in calculations

Even experienced professionals make these mistakes. Always check:

1. Wrong reflectance values. DIALux defaults are often higher than real-world values. A white ceiling is not 90% reflective — painted white drywall is more like 75-80%. Dark wood floors are more like 15-20%, not 30%. Wrong reflectances = wrong results.
2. Maintenance factor too high. Many calculations use 0.8 maintenance factor, meaning the design assumes the lighting will maintain 80% of its output over time. In dusty environments, or with infrequent cleaning, 0.7 or even 0.6 may be more realistic.
3. Using total lumens instead of delivered lumens. Always use fixture delivered lumens from IES files, not LED chip lumens from marketing materials.
4. Simplified geometry. A flat rectangular box is not a real room. Beams, columns, bulkheads, furniture, and partitions all affect real-world light distribution.
5. Ignoring daylight. For spaces with windows, daylight often provides most of the light during the day. Electric light calculations should consider both day and nighttime conditions.
6. Forgetting about reflected glare. Light reflecting off computer screens, glossy floors, and other surfaces is as much of a problem as direct glare.
7. Single point calculation only. Always look at the full false color map, not just the average value. A good average can hide very uneven distribution.

How Yakeen supports calculation work

We provide complete calculation support for architects, lighting designers, and MEP consultants working on projects with our fixtures. Our process:

1. You send us your plans, elevations, and project requirements
2. Our engineering team builds the DIALux model with our fixtures
3. We run calculations for each space type
4. We return the completed DIALux file plus a summary report with key metrics
5. We iterate with your team to optimize fixture selection and placement

This service is free for active projects. It ensures that our fixtures are correctly modeled, the calculations are accurate, and the design will perform as intended when installed.

For specifiers, this means you can be confident in the result before any fixtures are ordered. That is the value of engineering-led lighting specification.