Measure Light.
Design Intelligence.
DAo Studio transforms Daylight Factor data into precise occupancy-based illuminance metrics — enabling sensor-less smart lighting control under overcast sky conditions.
DAo Calculator
Enter your Daylight Factor measurements to instantly compute DAo and DAo.con for up to 20 sensor points.
Based on CIE Standard Overcast Sky · Lat 37°N · Schedule 08:00–17:00 · Threshold adjustable
Two Metrics. One Standard.
Both DAo and DAo.con use the CIE Standard Overcast Sky to evaluate daylighting performance independently of building orientation or location.
Overcast Daylight Autonomy
Measures the percentage of occupied time an indoor space reaches or exceeds the minimum illuminance threshold exclusively under overcast sky conditions.
Unlike traditional DA, DAo focuses on the most challenging scenario — the overcast sky. A DAo of 80% means that in 80% of occupied hours, the space has sufficient natural light without electric lighting.
Continuous Overcast Daylight Autonomy
An advanced version that not only measures when the threshold is met but also accounts for the degree to which illuminance falls below it — providing a more nuanced evaluation.
Where DAo simply counts hours that meet the threshold, DAo.con weights each hour by how well it performs. A point achieving 150 lux against a 300 lux target contributes 0.5 instead of 0.
| DAo | DAo.con | |
|---|---|---|
| Threshold behaviour | Binary (0 or 1) | Continuous (0 to 1) |
| Below-threshold penalty | Not counted | Partial credit given |
| Use case | Lighting control on/off | Dimming & smart control |
| Sensitivity | Lower | Higher |
Orientation & Location Independent
Because both metrics are derived from the Daylight Factor — a static geometric ratio — they do not depend on building orientation or geographic location. This simplifies evaluation significantly, focusing purely on architectural design.
Performance Curve
DAo and DAo.con as a function of Daylight Factor. Hover over the chart to explore values at any DF point.
Critical zone — DF below 1.5% gives DAo = 0%
DAo.con provides credit even below the DAo threshold
Scientific Foundation
Built on peer-reviewed research published in Leukos and Automation in Construction.
Fraction of occupied hours n_i where the indoor illuminance E_i (from Daylight Factor × outdoor overcast illuminance) meets or exceeds the threshold E_t.
Weighted average where each occupied hour contributes min(E_i / E_t, 1), giving partial credit to hours that fall below the threshold.
DFDaylight Factor — ratio of indoor to outdoor illuminance under overcast sky (%)E_tIlluminance threshold — typically 300 lux for task lightingE_iIndoor illuminance at hour i = DF × E_outdoor_overcast(i)NTotal occupied hours in the analysis periodn_i1 if E_i ≥ E_t, 0 otherwise (for DAo)Overcast Daylight Autonomy: A new concept to link daylight dynamic metrics with daylight factors.
Acosta, I.; Campano, M. A.; Domínguez-Amarillo, S.; Fernández-Agüera, J.
Leukos 15(4), 254–269
Dynamic analysis of office lighting smart controls management based on user requirements.
Campano, M. A.; Acosta, I.; Domínguez, S.; López-Lovillo, R.
Automation in Construction 133, 104021
Continuous Overcast Daylight Autonomy (DAo.con): A New Dynamic Metric for Sensor-Less Lighting Smart Controls.
Acosta, I.; Campano, M. A.; Domínguez-Amarillo, S.; Navarro, J.
Leukos 19(3), 343–367
Developed by I. Acosta and M. A. Campano · University of Seville · 2025
CIE Standard Overcast Sky
Uniformly overcast sky model. Luminance distribution: L(γ) ∝ (1 + 2 sinγ) / 3. Used as the reference sky for all calculations.
Daylight Factor
DF = Eᵢ / E₀ × 100%. Static ratio of indoor to outdoor illuminance under standard overcast sky. Orientation-independent.
Annual Integration
Summed over all occupied hours (08:00–17:00, Mon–Fri, break excluded) across the typical meteorological year.