Passively Actuated Systems

Designing a sustainable shading device for building retrofits.



Kinetic or responsive facades have been developed to improve buildings' daylighting conditions while mitigating energy consumption. Still, these facades require complex technology running on significant amounts of power and maintenance. Different projects have studied methods of creating kinetic shading devices that do not require electricity or central controls but still respond to environmental conditions. These methods are defined as passive dynamic systems, and their applications include thermo-bimetals, aerosol-based photobioreactors, or hygroscopic wood. This paper proposes a system powered by a passive actuator already used in the built environment. The actuator is derived from the heat engine or gas law apparatus physics principle, and it has been chiefly applied on automatic vent openers for greenhouses and passive solar trackers. This project proposes the integration of the actuator within a shading device and creates the methodology for finding the desired dynamic behavior through glare and illuminance simulations. The methodology is validated by improving indoor glare and thermal comfort on a retrofitting case study. This research is intended to test the louver physical model on-site, but this paper only begins to design the specifications needed for developing a passively actuated shading system.


Photo of Manuel Benitez Ruiz

Manuel Benitez Ruiz


Facade Tectonics Institute, Inc.

David Gerber

Associate Professor of Practice

USC School of Architecture


Introduction and Background

The most significant worldwide challenge for the coming decades is reversing the rate at which building energy demands are increasing, for instance, cooling structures in warm climates or lighting spaces for human health and comfort (Pombo, Rivela and Neila 2019) (Prieto, et al. 2018). While it seems reasonable to start designing more efficient new buildings, an astonishing 75% of all buildings in Europe are energy-inefficient, and only 0.4–1.2% of the whole stock is renovated each year (Pombo, Rivela and Neila 2019). Unless these buildings are retrofitted with sustainability in mind, the energy demands will increase exponentially. Focusing on retrofits is the first step to gaining significant energy savings and taking a step closer to reversing climate change.

The retrofitting of buildings has a high capacity to influence environmental impact and global climate change mitigation objectives. Building retrofits represent more than 17% of the primary energy savings potential of the EU for 2050 (Vilches, Garcia-Martinez and Sanchez-Montanes 2017). Within these projects, facades are one of the most significant building elements that affect the efficiency of these retrofits. In an industry that accounts for around 40% of the world's energy consumption (Pombo, Rivela and Neila 2019), facades regulate refrigeration and air conditioning loads (15% of the world's electricity consumption) (Prieto, et al. 2018), lighting (20-25% electrical energy use in buildings and the commercial buildings 30% to 50%) (Gerber and El Sheikh 2011), quality of views, psychological comfort, health, and productivity of individuals (Al Dakheel and Aoul 2017). Facades play an essential role in balancing these factors and offsetting their effect on the environment.

Within façades, glazing regulates the bulk of the energy that enters a space and the thermal energy trapped indoors. In fact, in most common scenarios of over-glazed buildings, daylight leads to a net increase in energy consumption since the needed cooling load exceeds the energy saved from reduced electric lighting (Mardaljevic, Heschong and Lee 2009). However, the impact of overglazing buildings has demanded strategies like shading devices to control heat gain, glare, and energy demands depending on the climatic zone and conditions (Al Dakheel and Aoul 2017). Fixed shading devices are the most common. However, even though they may be custom to the needs of the building, they are unable to adapt to external conditions and environmental variations. Most of the time, fixed shades result in blocking outside views.

Kinetic systems were developed for dealing with both energy and human comfort. However, since sensors and databases are crucial to responding to the building's need, they are disadvantaged against other fixed systems due to their dependency on electricity and high maintenance costs. Different studies in Life Cycle Analysis (LCA) indicate global tendencies where at least 40% of the impact associated carbon emissions come from the operational stage (Tafrihi 2018) (Chung, Kwok and Mardaljevic 2010) (Agency 2017). Reducing the operational impact of shading systems provides a potential improvement upon baselines.

Researchers have studied ways of designing devices with zero operational impact other than maintenance using environmental stimuli to activate and actuate these kinetic systems dynamically. Some examples include building envelope applications of thermo-bimetals (Sung 2018); aerosol-based photobioreactor converting vertical urban surfaces into cultivable land (Schmidt, et al. 2020); and HygroScope and HygroSkin, which can change their morphologies through the changes in humidity by hygroscopic material properties of wood (Kuru, et al. 2020). Most of these passive dynamic strategies are understudied due to their lack of applications in architecture. According to Doris Sung, thermobimetals have existed for decades. Still, their architectural applications are very primitive at the opening and closing of ventilation flaps, and nothing has been published on the development of building skins (Sung 2018).

This study does not intend to compete with existing passive strategies. This study presents the process and workflow for designing a passive dynamic shading system without wiring, sensors, or microcontrollers. The system consists of the heat engine or gas law apparatus, which is one of the classroom applications of the ideal gas law physics principle. It is composed of a closed system with a gas chamber/thermal can and a piston that reacts to temperature changes causing work. The ideal gas law provides a good approximation for the behavior of the gas trapped in the chamber and the resultant energy output. And, just like Sung's thermobimetal applications, the system shown in this paper has primitive uses on greenhouses and has not been thoroughly developed for building facades or retrofitting solutions.

Case Study Building

Located southwest on the University of Southern California Main Campus, near Downtown LA, the building consists of a 6-story apartment-like structure. Each unit contains a kitchen, a living room, a

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Research Questions

Passive strategies effectively control heat gain and glare in buildings and reduce cooling energy and cost in different climatic conditions. These strategies describe the reduction of carbon emissions through simulations

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The case study was first modeled in Revit using images captured from Google Earth, combined with floor plans and databases. The researcher's user experience was also used for material inputs

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Shading System and Mechanical Behavior

Figure 4. Left: Front view of shading device attached to the seismic bracing – shade rotated at 30 degrees. Figure 5. Right: Cross-sectional view of shading device – shade rotated

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Data Simulation

Figure 7. Variable relationship, simulation, and optimization methodology

The overall methodology of this study is detailed in Figure 7. The point-in-time used for this study was September 22, 2020 (September

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Results and Discussion

After plotting the rotation angles for imperceptible DGP, and the illuminance levels in Table 1, as shown in Figure 9, the desired mechanical behavior of the shading system (shade and

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While the daylight simulations on the study are simplified and may require more data points for more precise results, the workflow in Figure 7 was automated in a grasshopper script

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Thanks to USC Viterbi's independent research program and friends for academic support.

Rights and Permissions

Agency, UN Environment and International Energy. 2017. "Towards a zero-emission, efficient, and resilient buildings and."

Al Dakheel, Joud, and Kheira Tabet Aoul. 2017. "Building applications, opportunities and challenges of active shading systems: A state-of-the-art-review." Energies 1672.

Chong, Heap Yih, C Lee, and X Wang. 2017. "A mixed review of the adoption of Building Information Modelling (BIM) for sustainability." Journal of Cleaner Production 4114-4126.

Chung, Tse-Ming, Chun-Man Kwok, and John Mardaljevic. 2010. "A Study on Daylight Distribution and the Associated Heat Gain of a Typical Flat in Hong Kong Commercial Buildings." Journal of Light & Visual Environment.

Gerber, David Jason, and Mohamed El Sheikh. 2011. "Building Skin Intelligence: A Parametric and Algorithmic Tool for Daylighting Performance Design Integratio." Calgary: Association of Computer Aided Design of Architecture (ACADIA).

Housing, USC. 2019. Parkside Apartments (PKS). Accessed October 1, 2021.

Kuru, Aysu, Philip Oldfield, Stephen Bonser, and Francesco Fiorito. 2020. "A Framework to Achieve Multifunctionality in Biomimetic Adaptive Building Skins." Buildings.

Mardaljevic, J, L Heschong, and E Lee. 2009. "Daylight metrics and energy savings." Lighting research & technology 261-283.


Olsen, Heather, Eric Kennedy, and Jennifer Vanos. 2019. "Shade provision in public playgrounds for thermal safety and sun protection: A case study across 100 play spaces in the United States." Landscape and Urban Planning 200-211.

PASCO. n.d. Experiment Guide for the Model TD-8572: Heat Engine/Gas Law Apparatus. Accessed December 13, 2020.

Pombo, Olatz, Beatriz Rivela, and Javier Neila. 2019. "Life cycle thinking toward sustainable development policy-making: The case of energy retrofits." Journal of Cleaner Production 267-281.

Prieto, Alejandro, Ulrich Knaack, Thomas Auer, and Tillmann Klein. 2018. "Passive cooling & climate responsive façade design: Exploring the limits of passive cooling strategies to improve the performance of commercial buildings in warm climates." Energy and Buildings 30-47.

Radhi, Hassan, and Stephen Sharples. 2013. "Global warming implications of facade parameters: A life cycle assessment of residential buildings in Bahrain." Environmental Impact Assessment Review 99-108.

Schmidt, Timo, Carmen Herrmann, Michael Lakatos, Daniel Zabicki, Michael Wahl, and Kai Scherer. 2020. "Carbon-Dioxide-Inhaling Facade." Facade Tectonics 2022 World Congress. FTI.

Sung, Doris Kim. 2018. Skin Deep: Breathing Life into the Layer Between. Los Angeles: The American Institute of Architects.

Tafrihi, Elnaz and Abdel-Rahman, Amira. 2018. "Heat-actuated Auxetic Facades." Facade Tec (Fa).

Vilches, Alberto, Antonio Garcia-Martinez, and Benito Sanchez-Montanes. 2017. "Life cycle assessment (LCA) of building refurbishment: A literature review." Energy and Buildings 286-301.