Daylighting Art Galleries
: A Comparative Study of Four Roof Daylighting Systems (2026)
Having worked on numerous art gallery projects and built a private collection of my own, I have long been curious about which roof daylighting typology best serves the display and preservation of artwork. This study, conducted under Professor Mojtaba Navvab's lighting course at the University of Michigan, comparatively analyzes four roof daylighting systems—Flat Skylight, Clerestory, Light Monitor, and Sawtooth Roof—evaluating illuminance distribution, spatial uniformity, and direct sunlight penetration in gallery spaces through Lightscape simulation, under two solar altitude conditions (30° and 60°).
Four roof daylighting typologies were selected to span a deliberate range of performance: the Flat Skylight and Clerestory represent baseline, ratio-driven daylighting conditions common in conventional gallery design. The Light Monitor introduces an intermediate condition—daylight admitted indirectly through an elevated structure. The Sawtooth Roof serves as an upper-bound benchmark, using repetitive geometry to control both uniformity and direct sunlight. Together, these four typologies allow a controlled comparison of how roof geometry alone—independent of gallery size, wall height, or material reflectance—shapes the interior lighting environment.
All four typologies were tested on an identical base gallery model—same dimensions, wall height, and material reflectance—so that any difference in lighting performance could be attributed solely to the roof geometry itself. Illuminance simulations were run in Lightscape under two solar altitude conditions: 30°, representing a low-angle condition with long daylight duration and strong direct sunlight, and 60°, representing a high-angle condition where diffuse light dominates. Each typology was evaluated across four criteria: illuminance distribution, spatial uniformity, direct sunlight penetration, and wall exposure—the last being especially critical for gallery walls, where artwork is typically displayed.
Flat Skylight - Single overhead opening, direct top-down light
The Metropolitan Museum of Art (European Paintings galleries), Guggenheim Museum (central atrium)
Solar altitude 30°
Solar altitude 60°
Introduces strong top-down daylight through a single offset opening. Because the opening is positioned to one side, illuminance concentrates in a specific direction, producing high brightness near the opening while the opposite wall remains underlit—resulting in an asymmetrical distribution and low overall uniformity. Direct sunlight creates localized high-illuminance zones and pronounced contrast, with the position of light shifting significantly across solar altitudes. At 30°, light penetrates deeper at an oblique angle, intensifying the directional bias; at 60°, light enters more vertically, only partially mitigating the unevenness. This instability poses a real risk of photochemical damage to exhibited works.
Clerestory - A raised volume protrudes above the roof plane, with light entering through openings on both of its vertical sides
Museum of Modern Art Warsaw
Solar altitude 30°
Solar altitude 60°
Daylight enters through upper side openings on both sides, spreading toward the center in a laterally balanced pattern. Upper wall areas receive high illuminance while the floor gradually darkens, producing a vertical gradient. Compared to the Flat Skylight, bilateral entry improves overall uniformity to a moderate-to-high level. Direct sunlight is partially diffused by wall and ceiling surfaces, though localized brightness near the tops of exhibition walls remains a concern depending on artwork placement height. At 30°, light penetrates deeper with wider spread and stronger contrast; at 60°, light concentrates near the upper zones, softening the distribution and improving uniformity.
Light Monitor - An internal baffle sits below an open zenithal opening, so light enters from above and reflects off the baffle before diffusing indirectly into the space
Whitney Museum of American Art (eighth-floor galleries), Kimbell Art Museum (reflector-diffused vault lighting)
Solar altitude 30°
Solar altitude 60°
Daylight enters through an elevated monitor structure, reflecting off ceiling and wall surfaces before diffusing into the space. Higher illuminance occurs near the ceiling and upper zones, while the floor still receives relatively even illumination—producing a high degree of spatial uniformity. Direct sunlight is minimized or blocked entirely by the monitor's geometry, with walls receiving even illumination and no strong directional bias—conditions favorable for exhibition display. At 30°, light reflects and penetrates deeper with slight contrast near upper zones; at 60°, light spreads most evenly from above, producing the most stable condition of the three solar-angle tests for this typology.
Sawtooth Roof - Repeating ridge-and-glazing pattern across the roof
Broad Contemporary Art Museum at LACMA, Museo Jumex (Mexico City)
Solar altitude 30°
Solar altitude 60°
Repetitive sawtooth-shaped openings distribute light evenly across the ceiling, producing an even illuminance distribution with no strong localized hotspots—the highest spatial uniformity among all four typologies evaluated. The geometric configuration blocks or limits direct sunlight entry, allowing primarily diffuse light to reach the interior, minimizing glare and significantly reducing the risk of artwork deterioration. With no directional bias in wall illumination, conditions remain highly suitable for exhibition display across all wall surfaces. At 30°, light penetrates deeper but remains diffused; at 60°, light spreads evenly from above, achieving the most stable and uniform daylighting condition across all typologies and solar angles tested.
Conclusion
This study compared four roof daylighting typologies to examine how differences in geometric form and opening configuration influence interior illuminance distribution, spatial uniformity, and direct sunlight penetration in gallery spaces. The Flat Skylight produced the most concentrated and directionally biased illuminance pattern, with low uniformity. The Clerestory improved lateral balance through bilateral entry but retained a vertical gradient affecting display walls. The Light Monitor achieved high uniformity through indirect reflection while minimizing direct sunlight. The Sawtooth Roof demonstrated the highest overall performance, with an even, stable distribution and minimal direct sunlight across both solar altitude conditions. All four typologies showed greater contrast under low-angle (30°) conditions, with this effect most pronounced in the Flat Skylight and least significant in the Sawtooth Roof—underscoring its capacity to maintain stable performance across seasonal variation. Overall, roof systems relying on repetitive or indirect openings—the Sawtooth Roof and Light Monitor—are identified as the most suitable for gallery and museum environments, effectively suppressing direct sunlight while delivering high spatial uniformity, in alignment with preservation standards established by Thomson (1986) and the IES Lighting Handbook (2011).
Read the Full Paper
[Further Analysis: Grasshopper / Honeybee / Ladybug]
Lightscape, the software used in the original study, has since fallen out of common use in practice. As a follow-up, I tested whether a comparable illuminance analysis could be achieved through a more current, parametric workflow—using Rhino, Grasshopper, Honeybee, and Ladybug—to simulate point-in-time illuminance and annual Daylight Autonomy (DA) with real climate data (EPW files).
The simulation model was built through a ten-step process: constructing the base room geometry (HB Room from Solid), defining custom apertures (HB Aperture), assembling the model (HB Model), generating floor and wall sensor grids (HB Sensor Grid from Room / from Faces), merging sensor data (Mesh Join), importing climate data (LB Download Weather, LB Import EPW), defining sky conditions (HB CIE Standard Sky), running point-in-time and annual simulations (HB Point in Time Grid Based / HB Annual Daylight), and visualizing results as color-based heatmaps (LB Spatial Heatmap).
Under a June 2PM condition, peak illuminance reaches approximately 33,000–34,000 lux, with a highly concentrated bright zone at the center due to the high solar altitude. Under an October 2PM condition, illuminance drops to approximately 20,000–21,000 lux, with light entering at an angle and spreading directionally toward one side. Annual Daylight Autonomy remains high overall, at approximately 85–95%, indicating sufficient daylight availability but non-uniform distribution across the space.
Under a June 2PM condition, peak illuminance reaches approximately 28,000–30,000 lux, creating a concentrated light zone near the opening due to direct sunlight at high solar altitude. Under an October 2PM condition, illuminance drops to approximately 18,000–20,000 lux, remaining directional and extending deeper along one wall as sunlight enters at a lower angle. Annual Daylight Autonomy remains high overall (approximately 80–95%), indicating sufficient daylight but with uneven spatial distribution.