You can’t even calculate daylight properly, and you dare call yourself a lighting designer?

In modern architectural lighting design, no matter how advanced LED technology becomes, it cannot fully replace natural light.

Natural lighting not only saves energy but also enhances comfort, health, and spatial aesthetics.

So, how can we “use natural light well” in architectural design, rather than “abuse it”?

The greatest advantages of natural light are its dynamic nature and broad spectrum.

• Dynamism: As time and weather change, the brightness, color, and shadows within a space continually vary. This "living light environment" stimulates sensory interest—a rhythm often hard to replicate with electric light.
• Broad Spectrum: Natural light covers a continuous visible spectrum with excellent color rendering, presenting object colors truthfully. Industries such as art galleries, textiles, and printing workshops have long relied on natural light to ensure color accuracy.

1.2 Enhancing Work Efficiency and Mental Health

Numerous studies indicate:

• Office areas with window views boast higher employee productivity and lower turnover rates.
• Hospital patients recover faster when rooms have access to natural light.
• Improving natural light in school classrooms can enhance students’ academic performance and concentration.

1.3 Circadian Rhythms and Health

Short-wave blue light, abundant in natural light, is key to regulating melatonin secretion and circadian rhythm.

• Morning exposure to natural light effectively "resets the body clock";
• Lack of morning light delays nighttime melatonin secretion, making it harder to fall asleep;
• In high-latitude regions, lighting design is especially important in winter to compensate for the lack of natural light.

This provides a scientific basis for healthy lighting: natural light affects not only vision but also endocrine function and mental state.

1.4 Energy Saving and Sustainability

 
When combined with lighting control systems, natural lighting can reduce lighting energy consumption by 30–60%. Furthermore:

• For every 100W reduction in lighting load, about 30W of air conditioning cooling load is also reduced;
• Using high-performance glass and shading systems can balance lighting and insulation, avoiding the paradox where “energy-efficient lighting” leads to increased cooling energy consumption.

II. Design Objective: Balancing Comfort and Efficiency

 
The fundamental goal of natural lighting is not “the more light the better,” but rather:

• Meet visual and task requirements: ensure both horizontal and vertical illumination are adequate;
• Avoid glare and excessive solar exposure: Uncontrolled direct sunlight can cause thermal discomfort and visual interference;
• Avoid increasing energy load: Lighting must be optimized in coordination with heating/cooling systems.

This means lighting design must strike a balance between light environment quality and energy consumption control.

III. How to Achieve Good Natural Lighting Design?

3.1 Building Massing and Orientation

• South-facing (Northern Hemisphere): High-angle summer sun is easily controlled with overhangs; low-angle winter sun aids heating but requires adjustable louvers to prevent glare.
• North-facing: Light is stable and uniform but has the lowest illumination levels; often used in art studios and laboratories.
• East-West facing: Low-angle sunlight can cause strong glare and heat load; suitable for secondary functional spaces or transition areas.

Thus, elongated east-west volumes with north-south openings facilitate more balanced lighting.

3.2 Spatial Layout

• Classrooms and offices: Should be arranged facing south or north;
• Corridors and restrooms: Can be placed on east or west sides to reduce lighting demand;
• Atriums/light wells: Can serve as lighting cores, channeling natural light into deeper areas.

3.3 Facade and Shading

 
Shading systems are crucial to lighting design:

• Horizontal shading (overhangs, light shelves): Suitable for south facades, blocking high-angle summer sun;
• Vertical shading (louvers, fins): Suitable for east-west facades, reducing low-angle direct sunlight;
• Light shelves: Reflect sunlight onto the ceiling, diffusing it deeper into the space while reducing window-background contrast for improved comfort.

3.4 Material and Glass Selection

 
Glass properties directly affect lighting quality:

• Visible Transmittance (VT): Higher values improve lighting efficiency but may increase glare risk;
• Solar Heat Gain Coefficient (SHGC): Lower values reduce cooling load;
• Light-to-Solar Gain ratio (LSG = VT/SHGC): High LSG glass suits hot climates; low LSG glass suits cold climates;
• Diffused/frosted glass: Suitable for overhead lighting, effectively reducing discomfort from direct light.

3.5 Indoor Surface Reflectance

 
Higher reflectance improves lighting depth and uniformity. IES recommended values:

Material selection should balance function, aesthetics, and optical properties.

IV. Daylight Analysis Software and Metrics Workflow

4.1 Key Metrics Overview

• sDA300/50%: Spatial Daylight Autonomy – percentage of floor area that receives at least 300 lux for 50% of annual working hours.
• ASE1000/250: Annual Sunlight Exposure – percentage of floor area exposed to more than 1000 lux for at least 250 hours per year (limits overexposure).
• DGP (Daylight Glare Probability): Evaluates glare using HDR fisheye images; sensitive to eye position, view direction, and specular angles (often evaluated with evalglare).
• CBDM (Climate-Based Daylight Modeling): Uses local annual weather data for hourly daylight calculations, forming the basis for the above dynamic metrics.

In practice: sDA + ASE quantify “usable and not overexposed,” while DGP assesses “whether glare is present.”

4.2 Tool Selection (by Phase)

 
(This section is mainly a list of software, it is recommended to make a table in Word)

4.3 Recommended Workflow (can serve as “Delivery SOP”)

• Step 1 | Conceptual Sensitivity Analysis: Use CBDM to batch analyze window-to-wall ratio, shading geometry, glass (VT/BSDF), reflectance, etc.; output sDA/ASE heatmaps and “compliance area vs. window-to-wall ratio” curves.
• Step 2 | Scheme Finalization: Conduct DGP evaluations from multiple viewpoints (sitting/standing, facing/back/side window), identifying seasonal/time/orientation glare peaks; introduce adjustable shading if needed and recalculate.
• Step 3 | Detailed Coordination: Use OpenStudio/IES VE to integrally assess daylighting, electric lighting, energy use, and control strategies. Document zones, sensor height, illuminance thresholds (e.g., 300/500 lux), and dimming curves in technical specifications.
• Step 4 | Lighting Coordination: Use AGi32 to produce engineering drawings combining electric lighting and typical daylight conditions. For annual metrics, transfer geometry to Licaso to aggregate DA/UDI/sDA/ASE.
• Step 5 | Compliance and Submission: Submit sDA300/50% and ASE1000/250 compliant areas, parameters, and occupancy schedules; include DGP screenshots and control strategies for key viewpoints as evidence of glare control.

4.4 Common Pitfalls and Checkpoints

• Geometry/Grid: Model mullions, window frames, and ceiling reflective surfaces; sensor grid spacing ≤0.6 m, keep ≥0.5 m from walls to avoid sampling gaps.
• Material Models: Prefer BSDF for complex shading/functional glass; using only “transmittance” can lead to inaccuracies.
• Weather Files: Use consistent EPW/TMY sources and time zones; ensure identical occupancy periods when comparing across tools.
• Glare Viewpoints: DGP is highly sensitive to eye position and view direction; cover offices (sitting), corridors (standing), and both facing and away from windows.

V. Whole-Process Control: From Design to Operation

• Determine the space's function and task illumination;
• Clarify tolerances for field of view and glare;
• Develop space zoning and daylighting objectives.

3. Deepening design

4. Construction and Documentation

5. Debugging and operation and maintenance

Use Light Wisely, Not Just Abundantly

 
Natural lighting is a comprehensive system: it involves architectural form and spatial layout, lighting science, and profoundly affects human health and behavior.

 
Truly successful natural lighting design is not about flooding interiors with light, but rather:

• Meeting functional needs: providing comfortable visual conditions;
• Optimizing health: supporting circadian rhythms and enhancing mental state;
• Achieving energy efficiency: reducing electricity use and carbon emissions;
• Enhancing aesthetics: integrating light and architecture.

Light is the soul of architecture. The best way to make a building “breathe” is to make natural light an integral part of the space.