Lighting Design and Daylighting Design:Lessons from the Butterfly Roof of Changi Airport Terminal 3
“Natural daylight is the finest light available to us. Yet it must be tamed so that it becomes an asset rather than a disturbance.”
Pencahayaan alami yang dinamis di area publik membuat ruangan lebih indah serta menyehatkan
When Architecture Responds to Nature
How the Butterfly Roof Transforms Sunlight into a Human-Centered Spatial Experience
The moment I stepped into Terminal 3 of Changi Airport, I immediately sensed that this airport was unlike any other I had experienced. It wasn't simply because of its vast scale or impressive architecture. The building itself felt alive.
Natural light shifted gently with the changing sky. Indoor temperatures remained remarkably stable despite the enormous glass roof overhead. Most surprising of all, the terminal felt extraordinarily calm, even as thousands of passengers moved continuously through the space.
As a Human-Centered Building Performance Consultant, that experience immediately raised a technical question in my mind. How can a public space of this scale simultaneously provide visual comfort, thermal comfort, and acoustic comfort? The answer, as it turned out, was hidden directly above us. A sophisticated Responsive Dynamic Daylighting System known as the Butterfly Roof.
What Is the Butterfly Roof?
The Butterfly Roof is a responsive Dynamic Daylighting System that integrates movable reflector panels, daylight sensors, Low-E glazing, and automated artificial lighting to optimize natural daylight, reduce unwanted solar heat gain, and enhance visual, thermal, and acoustic comfort throughout the building.
Rather than treating sunlight as something that must be blocked, the system intelligently controls how daylight enters the building—transforming it into a valuable environmental resource.
This approach represents one of the most compelling examples of Architectural Daylighting Design, where Lighting Design, Building Physics, and Building Automation operate together as an integrated building system.
Why Did Changi Airport Adopt the Butterfly Roof?
The Butterfly Roof at Changi Airport Terminal 3 is far more than an iconic architectural feature.
From a Building Physics perspective, it represents an integrated environmental system designed to balance energy efficiency, occupant comfort, and long-term sustainability within a single architectural solution.
As one of the world's busiest international airports, Changi Airport Group (CAG) needed a terminal capable of remaining bright, comfortable, and energy-efficient throughout the day while minimizing the environmental impact of operating such a massive facility.
When Terminal 3 opened in 2007, CAG introduced the Responsive Dynamic Daylighting System through its Butterfly Roof—an innovative strategy that continues to define the building's environmental performance.
This design philosophy also aligns closely with the global effort to combat climate change.
Through the Paris Agreement, more than 190 countries committed to limiting global temperature rise to well below 2°C, while pursuing efforts to keep warming below 1.5°C.
The building sector is estimated to account for approximately 37% of global carbon emissions, making passive design strategies, daylight optimization, and high-performance building envelopes essential components of global decarbonization efforts.
The Butterfly Roof addresses these challenges by maximizing the use of natural daylight, reducing solar heat gain, and lowering the demand for electric lighting and mechanical cooling.
The result is more than a comfortable environment for millions of passengers every year.
The system also reduces carbon emissions by approximately 2.4 million kilograms of CO₂ annually, supporting Changi Airport Group's Net Zero Carbon Roadmap.
In other words, the Butterfly Roof was never intended merely as an architectural statement.
It was conceived as a Building Physics solution—one that transforms sunlight into an intelligently managed resource for the benefit of both people and the environment.
When the Sun Becomes Part of the Building System
Above the skylights of Changi Airport Terminal 3, 919 butterfly panels are installed and continuously controlled by daylight sensors and the Building Management System (BMS).
Rather than allowing direct sunlight to flood the terminal, the system constantly adjusts the angle of each reflector panel in response to changing sky conditions.
The butterfly panels do far more than simply open and close.
They function like a giant optical instrument, precisely controlling how daylight enters the building.
As Christian Bartenbach explains, the objective is not to block sunlight altogether, but to "tame" it—allowing only the highest quality of natural light to reach occupants.
What enters the terminal is not harsh direct sunlight, but diffused daylight—sky light that has been scattered by the atmosphere, producing soft, uniform illumination that is comfortable for the human eye.
This is one of the defining principles of Daylighting Design: not maximizing the quantity of daylight, but optimizing its quality.
Perforated Metal Panel Dinamis yang bisa terbuka dan tertutup di seluruh area ceiling
A Responsive Integration of Lighting, Daylighting, and Thermal Comfort
The Butterfly Roof is much more than a collection of movable reflector panels.
It is a Responsive Dynamic Daylighting System composed of four interconnected technologies that work together continuously to maintain visual comfort, thermal comfort, and energy efficiency under constantly changing sky conditions.
Butterfly Panels (919 Units)
The butterfly panels regulate both the amount and direction of incoming daylight using daylight sensors integrated with the Building Management System.
Throughout the day—and across every season—the panels continuously adjust their position to ensure that indoor daylight remains balanced, comfortable, and glare-free.
Instead of reacting to the sun alone, the system responds to the overall luminance of the sky, creating a naturally illuminated environment that remains consistent despite changing weather conditions.
919 Butterfly Panel diletakan pada Roof Top Terminal 3 Changi Airport untuk mengatur tingkat cahaya langit yang masuk ke ruangan
Direct Artificial Lighting
High-intensity luminaires are positioned directly beneath the butterfly panels. During nighttime or periods of extremely low daylight availability, these fixtures seamlessly replace natural daylight, maintaining a consistent lighting character throughout the terminal.
As a result, passengers experience virtually no abrupt transition between daytime and nighttime lighting conditions. The architecture preserves the same visual atmosphere regardless of the time of day.
Light Projection dengan kekuatan 1000 Watt
Double Low-E Glazing
The Butterfly Roof incorporates double Low-E glazing, designed to minimize solar heat transfer while maintaining high visible light transmission. This allows abundant natural daylight to enter the building without introducing excessive radiant heat.
From a Building Physics perspective, this separation of visible light from infrared radiation is essential for creating energy-efficient buildings in tropical climates.
Dynamic Perforated Metal Ceiling
Beneath the daylighting system is a dynamic perforated metal ceiling that performs two critical functions simultaneously.
First, it reduces glare by controlling how daylight is distributed throughout the interior.
Second, it enhances acoustic comfort by absorbing reflected sound and reducing reverberation within the vast terminal space.
This multifunctional architectural element demonstrates how a single design component can improve both lighting performance and acoustic performance at the same time.
Together, these four layers form a highly integrated Building Physics strategy that exemplifies Architectural Daylighting Design, where Lighting Design, Building Automation, and environmental engineering operate as a unified responsive system.
Rather than functioning as isolated technologies, each component continuously interacts with the others to create an indoor environment that adapts naturally to changing external conditions.
The Harmony of Three Human Comforts
Perhaps the most remarkable aspect of the Butterfly Roof is that it does far more than control daylight.
It represents a Building Physics strategy that simultaneously integrates the three fundamental dimensions of human comfort:
Visual Comfort
Acoustic Comfort
Thermal Comfort
Together, these environmental qualities shape the way people perceive, navigate, and experience architectural space.
Visual Comfort
"Everything Is Clearly Visible"
In tropical climates, large skylights are often associated with one inevitable problem: glare.
Yet my experience inside Terminal 3 was exactly the opposite.
Despite spending an extended period beneath an expansive glass roof, my eyes never felt fatigued.
Technically, the butterfly panels regulate luminous intensity by reflecting direct sunlight—the primary carrier of excessive solar radiation—while allowing only diffused daylight to enter the terminal.
Before reaching the occupied space, this daylight then passes through the double Low-E glazing, further improving lighting quality while reducing unwanted heat gain.
The result is remarkably uniform illumination with the naturally high Color Rendering Index (CRI) that only daylight can provide.
Materials, vegetation, signage, and even facial expressions appear vivid and clear without excessive contrast or distracting glare.
This exceptional visual clarity also enhances spatial orientation, helping millions of passengers navigate the terminal more intuitively every year.
Perforated Metal Panel Dinamis ini berfungsi untuk mengurangi silau cahaya dan meningkatkan kenyamanan akustik ruangan
Acoustic Comfort
"Calm Amidst the Crowd"
The next sensation I noticed was silence.
My eyes could see thousands of people moving continuously through the terminal.
Yet my ears never perceived the overwhelming level of noise one would normally expect inside a public space of this magnitude.
The explanation lies within the Dynamic Perforated Metal Ceiling, installed across much of the terminal.
These perforated metal panels function as highly effective sound absorbers, reducing reflected sound energy and maintaining controlled reverberation times throughout the space.
Their geometry can also be adjusted to help distribute daylight from the skylights more effectively.
In other words, a single architectural element performs two essential environmental functions simultaneously:
Visual Comfort.
Acoustic Comfort.
Without this integrated system, a terminal the size of Changi Airport Terminal 3 would likely suffer from excessive echoes, overlapping public announcements, and a far more mentally exhausting passenger experience.
Thermal Comfort
"Comfort You Don't Notice"
Standing beneath a glass roof as large as that of Terminal 3, most people would naturally expect to feel intense radiant heat.
Yet my own experience was the complete opposite.
At no point did I feel the harsh solar heat that typically accompanies extensive glazing in tropical climates.
The secret lies in the building's double Low-E glazing.
Its microscopically thin coating reflects much of the sun's infrared radiation while still allowing visible daylight to pass through.
In simple terms:
Light passes through. Heat stays outside.
This thermal stability significantly reduces the cooling load placed on the HVAC system, enabling the terminal to maintain comfortable indoor temperatures while consuming substantially less energy.
The result is not only improved energy efficiency, but also a more comfortable and healthier indoor environment for millions of passengers every year.
How Does the Butterfly Roof Work?
The Butterfly Roof is designed to follow the rhythm of nature.
As sky conditions change throughout the day—whether due to the movement of the sun, passing clouds, or the transition from day to night—the system continuously adjusts each of its components to ensure that the terminal remains bright, comfortable, cool, and free from glare.
The result is a remarkably consistent indoor experience.
Passengers rarely realize that the building is constantly adapting to its surrounding environment. Behind the scenes, however, the Responsive Dynamic Daylighting System is continuously balancing daylight, thermal performance, and energy consumption in real time.
This is one of the defining characteristics of Human-Centered Building Performance: the technology becomes virtually invisible, while human comfort remains consistently perceptible.
Sunny Conditions
When solar radiation reaches its highest intensity, the butterfly panels rotate to predetermined angles, reflecting direct sunlight away from the building. Only diffused daylight—light that has already been scattered by the atmosphere—is allowed to enter the terminal.
At the same time, the double Low-E glazing filters much of the incoming infrared radiation, while the dynamic perforated ceiling controls glare and distributes daylight more evenly throughout the space.
Instead of fighting the tropical sun, the building intelligently manages it. The objective is not to eliminate daylight, but to preserve its visual benefits while minimizing its thermal penalties. This represents one of the core principles of Daylighting Design: maximizing useful daylight while controlling heat gain and visual discomfort.
Sunny Condition
During periods of intense solar radiation, the Butterfly Roof adjusts to a specific angle, reflecting direct sunlight while admitting only atmosphere-diffused daylight into the building.
Residual solar heat is significantly reduced by the double Low-E glazing, while the dynamic perforated ceiling mitigates glare and optimizes daylight distribution throughout the interior.
Overcast Conditions
When the sky becomes overcast, the daylight available outdoors is softer but less intense. In response, the butterfly panels open wider, allowing a greater volume of diffused daylight to enter the terminal. Because the incoming light is already naturally scattered by clouds, the building can harvest it efficiently without introducing excessive glare.
The result is a spacious interior that remains bright and evenly illuminated, even on cloudy days, while reducing dependence on electric lighting. Rather than reacting to sunlight alone, the Butterfly Roof continuously responds to changing sky luminance, ensuring that interior lighting conditions remain stable regardless of the weather.
Overcast Condition
During overcast conditions, the Butterfly Roof opens fully, allowing the full spectrum of diffused skylight to enter the interior space.
Nighttime Operation
As evening falls, the butterfly panels close and the Direct Artificial Lighting system positioned beneath them gradually assumes the role previously performed by natural daylight. Rather than creating a dramatically different nighttime environment, the artificial lighting has been carefully designed to replicate the character of daylight established during the day.
Passengers therefore experience a seamless visual transition between daylight and electric lighting.
The architecture maintains a consistent atmosphere regardless of the hour. This continuity demonstrates that successful Lighting Design extends beyond selecting luminaires—it requires creating a cohesive visual experience throughout the entire daily cycle.
During Night Time
At night, the Butterfly Roof panels close, and the space is illuminated by direct artificial lighting positioned beneath the butterfly panels.
Performance Validation Through Daylight Simulation
In professional practice, systems as sophisticated as the Butterfly Roof are never designed solely through intuition. Their performance is typically validated using advanced daylight simulation software, including: Radiance, ClimateStudio, Honeybee and DIALux.
These simulation platforms allow designers to predict and optimize daylight performance long before construction begins.
Key performance metrics commonly evaluated include:
Spatial Daylight Autonomy (sDA) — measuring the percentage of occupied floor area receiving sufficient daylight throughout the year.
Annual Sunlight Exposure (ASE) — identifying areas that may experience excessive direct sunlight and potential glare.
Useful Daylight Illuminance (UDI) — assessing how frequently daylight levels remain within the range considered comfortable and beneficial for occupants.
Combined with analyses such as Solar Heat Gain, these tools enable architects and engineers to optimize visual comfort, thermal performance, and energy efficiency simultaneously.
Rather than relying on assumptions, contemporary Architectural Daylighting Design is increasingly driven by measurable performance and evidence-based design decisions.
A Human-Centered Architectural Philosophy
The architects at Skidmore, Owings & Merrill (SOM) did not design Terminal 3 merely as a transportation hub.
They envisioned it as a public space capable of responding intelligently to natural environmental cycles.
This philosophy is reflected in the seamless integration of daylight, landscape, architectural structure, and automated building systems, all working together as a single environmental ecosystem.
Instead of resisting the tropical climate, the terminal embraces it.
Sunlight is no longer treated as an environmental problem to be excluded from the building.
It becomes a valuable natural resource—carefully controlled through Building Physics, Lighting Design, and Building Automation to improve both human comfort and environmental performance.
To me, this represents the true essence of Human-Centered Building Performance.
A high-performance building should do more than satisfy functional requirements.
It should actively support human physiological and psychological well-being through the careful orchestration of light, sound, temperature, and spatial experience.
The greatest architectural achievements are often those that occupants never consciously notice.
People simply feel more comfortable.
They see more clearly.
They remain cooler.
They hear conversations more easily.
And they instinctively enjoy spending time within the space—without ever realizing how much engineering is quietly working on their behalf.
Tabel Manfaat Responsive Dynamic Daylight System
Lessons for Tropical Architecture in Indonesia
From a climatic perspective, Indonesia and Singapore share many of the same environmental characteristics.
Both experience abundant solar radiation, high temperatures, elevated humidity, and intense daylight throughout the year.
Ironically, however, tropical architecture often continues to regard sunlight as an enemy rather than an opportunity.
As a result, many buildings are designed with heavily shaded façades, limited daylight penetration, artificial lighting operating throughout the day, and extensive dependence on mechanical air conditioning.
Yet the real challenge is not how to avoid sunlight.
It is how to control it intelligently.
This is precisely where Daylighting Design becomes essential.
By combining daylight simulation with measurable performance metrics—such as Spatial Daylight Autonomy (sDA), Annual Sunlight Exposure (ASE), Useful Daylight Illuminance (UDI), and Solar Heat Gain analysis—architects and engineers can design buildings that are:
Naturally bright
Energy efficient
Visually comfortable
Thermally comfortable
Responsive to tropical climates
Better aligned with human well-being
Instead of relying on intuition alone, these performance-based design tools allow daylight to become an integral component of the building's environmental strategy.
The Butterfly Roof demonstrates that Building Physics, Architectural Daylighting Design, Lighting Design, and passive environmental strategies can work together to create buildings that are healthier, more efficient, and more sustainable.
More importantly, it reminds us that tropical architecture should not merely protect occupants from nature.
It should learn to collaborate with it.
Reflection
During my visit to Changi Airport Terminal 3, I came to realize that the most successful buildings often achieve their greatest accomplishments through things we never consciously notice.
We don't notice that daylight is being continuously managed.
We don't notice that echoes are quietly being absorbed.
We don't notice that solar heat is being reflected away before it reaches us.
What we notice is something much simpler.
A space that feels comfortable.
To me, that is where truly great design reveals itself.
The best architecture is not necessarily the one that appears the most spectacular.
It is the one that protects people so naturally that its presence never feels imposed.
The Butterfly Roof at Changi Airport Terminal 3 demonstrates that when Building Physics, Daylighting Engineering, Lighting Engineering, Thermal Engineering, and Building Automation are conceived as a single integrated system, the result extends far beyond energy efficiency.
It creates spaces that are healthier.
More comfortable.
More beautiful.
And ultimately, more human.
For architects, engineers, developers, and building owners working in tropical regions, the Butterfly Roof offers more than an inspiring architectural precedent.
It provides a practical lesson in how Human-Centered Building Performance can transform natural daylight into a measurable contributor to occupant well-being, environmental sustainability, and long-term building performance.
As climate challenges continue to intensify and expectations for healthier buildings continue to rise, the future of tropical architecture will depend not on resisting nature, but on designing buildings that respond intelligently to it.
From my perspective as a Human-Centered Building Performance Consultant, this is perhaps the most valuable lesson offered by Changi Airport Terminal 3.
Architecture reaches its highest potential when technology becomes invisible, while human comfort becomes unforgettable.
Project Information:
Project Name: Changi Airport, Terminal 3, Singapore [SG] completion 2007
Architects SOM: Skidmore, Owings & Merrill LLP , New York [US], CPG Corporation Pte Ltd, Singapore [SG]
Lighting Designer: Bartenbach LichtLabor, Aldrans [AT]
Photography: Bartenbach, durlum GmbH, David Phan, iStock: Pinopic, Joyt, Fotolia: Chrupka, Herwin Gunawan
References
Bartenbach LichtLabor. (n.d.). Daylighting and lighting design research. Innsbruck, Austria: Bartenbach LichtLabor.
Changi Airport Group. (Various years). Sustainability Report. Singapore: Changi Airport Group.
International Commission on Illumination (CIE). (2006). CIE 170:2006 – Daylight in Buildings. Vienna, Austria: CIE.
Illuminating Engineering Society (IES). (2020). The Lighting Handbook (11th ed.). New York, NY: Illuminating Engineering Society.
Skidmore, Owings & Merrill LLP (SOM). (2008). Singapore Changi Airport Terminal 3 – Project Description. Chicago, IL: Skidmore, Owings & Merrill LLP.
