the City

Combating heat islands with modular clouds









2018 - ongoing


Framlab, Lysverk


Andreas Tjeldflaat, Kabir Sahni, Elise Park

Modular, Housing, Product Design, Architecture

Our cities are heating up nearly twice the global average rate. By 2050, the urban population exposed to extreme temperatures is estimated to increase by 800 percent. Even at the current levels, heatwaves are the deadliest of all climate risks. Oversky is a design research project that explores the capacity of a levitation system to alleviate the heat island effect of cities and free up space for its citizens. Inspired by clouds, the modular system can float over and counteract the effect of the areas largely responsible for the heat buildup, road networks and parking lots, reclaiming this space for people.

The Gravity of Clouds. ​In the ancient Greek comedy, The Clouds, written by Aristophanes, the philosopher Socrates declares that the Clouds are the only true deities. In the play, the clouds shape-shift to reveal the true nature of whoever is looking at them and are hailed as masters of poetry and rhetoric.

Due to the complexity of cloud dynamics, there is still an element of mystery and uncertainty to the behavior of clouds. Clouds have a significant effect on the climate system through variables such as cloud cover, duration, thickness, and altitude. However, because the behavior of tiny aerosol particles largely determine these properties, clouds are notoriously difficult to simulate in models, requiring the use of proxy data in global climate models. Following new research, recent climate models have altered their treatment of clouds, uncovering alarming findings . The new predictions overturn a long established consensus about the climate sensitivity of the planet. While most leading climate models still correlate a doubling of CO  in the atmosphere to a 1 degree C global temperature increase, the matter is complicated by a series of external variables. There are three primary feedbacks caused by the natural systems in response to initial warming: the melting of ice and snow; the additional atmospheric water vapor; and, the most uncertain, the behavior of clouds.





'Skyer', Niclas Gulbrandsen.


We generally think of clouds as keeping us cool, but this is not always the case. Clouds such as Marine Stratus and Stratocumulus shade roughly one fifth of the oceans, cooling the Earth by reflecting solar radiation that hits them back into space. The higher Cirrus clouds, on the other hand, are thin enough to let sunlight through while preventing heat from escaping as infrared radiation, effectively acting as insulating blankets. As a general rule, low, thick clouds reflect sunlight, while high, thin clouds trap heat below them. It has been determined that a warming Earth will push clouds upward and poleward, allowing for more solar energy to warm the earth . Researchers at Caltech    have argued that global cloud cover may have a tipping point, beyond which clouds would “become unstable and break up,” sending global warming into overdrive.




The cloud formations connect to the street below and link adjacent city blocks, complementing the ordered grid of the city with an adaptable, three-dimensional connective tissue

Hot in the City. There are certain areas that are significantly more vulnerable to the effects of global warming than previously predicted. Climate models have, up until this point, lacked an accurate representation of urban areas at a global scale. A team of researchers  have recently created a new model that includes comprehensive climate projections for cities, suggesting that hotter cities could be devastating for urban public health. In a “business as usual” scenario, cities could warm as much as 4.4 degree C by the year 2100, according to this model. Even in a scenario of substantial mitigation of greenhouse gas emissions, a large number of cities will experience warming of more than 1.5 degree C, the target set by the Paris Agreement. According to the WHO, heatwaves are among the most dangerous of natural hazards, but rarely receive adequate attention because their death tolls and destruction are not always immediately obvious. Between 2000 and 2016, the number of people exposed to heat waves increased by 125 million .




The kit-of-parts consist of five cloud modules in addition to a series of distinct infrastructural links, connecting the streetscape below with the cloudscape above.

The system is intended to reclaim space for people from the vast areas given up to vehicles and infrastructure in cities.

Cities make up less than 3% of the land area of the earth, yet accommodate more than half of its population. The climate in urban areas is distinctly different from that in surrounding rural areas, due to what is known as the heat island effect. This condition is a consequence of how cities have been designed, as tall buildings, paved roads, and other infrastructure absorb and release the heat of the sun. The contemporary city is a high-density organism, designed for efficiency and divorced from nature. The majority of its open space is inaccessible to people and strictly delineated for vehicular transit and parking. This network of concrete and asphalt jeopardizes the quantity and quality of public space, with only a few plazas, parks, and green patches drizzled across the city. The open space of the contemporary city is by and large the right of engines, not people.

The system is designed to reduce heat buildup in cities by reflecting solar radiation and through evaporation of collected rain water.


A Cool Intervention. Oversky is a project that seeks to intervene in this scenario, reducing heat buildup in cities while reclaiming space for people from the vast areas given up to vehicles and infrastructure. The project consists of a modular system of volumes that can float within urban chasms, forming space for public imagination and expression. The formations connect to the street below and link adjacent city blocks, complementing the ordered grid of the city with an adaptable, three-dimensional connective tissue. Modular archipelagos of space become cultural centers, classrooms, art studios, commercial satellites, parks, pools, and cinemas, responding to local needs of neighborhoods while giving the city back space lost to transit networks. Space that invigorates city energy, culture, and collective activities.

The structure is designed to form cloud-like clusters, providing shade for the city by reflecting heat from the sun. In addition, the top surface is configured to channel and collect rain water that can be stored in integrated and below-grade tanks and released as mist into the air. This provides additional cooling and helps with stormwater management for the city. With the use of a titanium dioxide coating, the outer surface is able to clean the air through breaking down nitric and nitrogen oxides when hit by sunlight. The bottom surface is designed to combat a different kind of pollution as it absorbs noise from the traffic below.




F. Rainwater Collection Modules
G. Precipitation
H. Mist

I. Reflected Solar Radiation


A. Public Space Modules
B. Lift-gas Modules
C. Cloudscape Garden
D. Streetery Link
E. Access Link


In accordance with Archimedes’ principle, the structure levitates on the principle of buoyancy. With a significant volume dedicated to lift gas – a lighter than air substance – the structure generates a lift equal to the weight of the displaced air, minus the weight of the structure. In addition, the structure is supported with a set of distinct infrastructural links, connecting the streetscape below with the cloudscape above. These links are designed to celebrate the entry points to the space above, while activating the street through various functional and programmatic contributions, from playgrounds and parks to pop-up restaurants.

On a parting note, it is important to underscore that Oversky is not proposed as a silver bullet solution for reducing heat buildup in urban areas. Rather, the system is intended to form part of a city’s greater resilience and heat mitigation strategy. This strategy needs to include comprehensive plans for increasing the city’s blue and green infrastructure, be sensitive to the heat vulnerability of its neighborhoods, and work alongside a host of measures addressing root causes of the climate crisis.




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1. Pearce, F., Why Clouds Are the Key to New Troubling Projections on Warming. Yale Environment 360, Yale School of the Environment, February 5, 2020,
2. Norris, J., Allen, R., Evan, A. et al. Evidence for climate change in the satellite cloud record. Nature 536, 72–75 (2016).
3. Schneider, T., Kaul, C.M. & Pressel, K.G. Possible climate transitions from breakup of stratocumulus decks under greenhouse warming. Nat. Geosci. 12, 163–167 (2019).
4. Zhao, L., Oleson, K., Bou-Zeid, E. et al. Global multi-model projections of local urban climates. Nat. Clim. Chang. 11, 152–157 (2021).
5. Watts, N., Amann, M., Arnell, N., et al. The 2020 report of The Lancet Countdown on health and climate change: responding to converging crises. Lancet. 2021 Jan 9;397(10269):129-170. doi: 10.1016/S0140-6736(20)32290-X. Epub 2020 Dec 2. Erratum in: Lancet. 2020 Dec 14;: PMID: 33278353.

6. Skyer, Niclas Gulbrandsen. Illustrastion for H. Holm, "Soga um kapergastane og deira våde-råm", Oslo 1968. The National Museum of Art, Architecture and Design, Norway

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