Global warming and related crises have pushed the architectural community to focus on sustainable design solutions in recent years. Providing thermal comfort is a major energy consumption area in buildings, especially in hot climatic zones where cooling is critical.

Before the industrial revolution, passive cooling strategies were integral to vernacular and traditional architecture, particularly in hot climate regions. These strategies utilized natural forces and environmental elements to achieve thermal comfort. Understanding and deploying passive cooling strategies is essential for designing buildings that are less dependent on fossil fuels.

We examine the main strategies for cooling buildings: shading, convection cooling, evaporative cooling, radiative cooling, geo-cooling, and greening – all illustrated with innovative examples from previous winners of the Holcim Foundation Awards competition.

Shading is the simplest and most fundamental way of cooling a building by preventing excess heat from entering indoor spaces. An effective shading design provides pleasant daylight and privacy while avoiding overheating or glare. Various types of shading methods are based on their place of installation, with outdoor shades being more efficient than indoor ones. The entire building mass can be designed to create self-shade, depending on its form. Window shades can be horizontal, vertical, recessed, solid, seasonal, or fixed - as well as solid or louvered, and internal or external. The design and materials used for glazing can also significantly impact the effectiveness of a shading system.

Empowering the Homeless in the Philippines is a project that uses a self-financing model combining social housing for homeless families with a solar power plant that produces and sells energy to finance the homes. Conceived to provide adequately comfortable living conditions to 125 homeless families, the design turns the rooftops of the houses into a mini 2.5 MW photovoltaic plant able to generate 25 times more electricity than the residential complex will use.

The large roof overhang housing the PV panels reduces heat gain. The integrated solar roofing system includes insulation and allows hot air that rises from the dwelling to dissipate between the sandwich layers as a climate adaptive building skin. The array of passive design strategies minimizes the consumption of electricity, ensuring a high proportion of generated electricity is available for resale.

Cooling by convection is based on the simple principle that warm air rises and cool air sinks. Natural ventilation, stack (chimney) effect, and cross ventilation are effective passive strategies that cool buildings by replacing warm air with fresh air. These strategies are facilitated by appropriate openings, clerestory windows, roof ventilators, wind scoops, wind towers, atriums and wind catchers – which are particularly effective in capturing outdoor cool breezes or venting indoor warm air.

Articulated Site in Colombia or UVA de La Imaginación project centers on creating high quality public spaces inserted into low-income, dense neighborhoods at a reservoir where two giant water tanks have been replaced by new infrastructure. The obsolete tanks are repurposed to create public space, taking inspiration from the site’s history, surrounding topography, and structure of existing tanks and pools.

The project was designed for Medellín’s year-round hot and humid climate with permeable walls throughout the perimeter of the building that allow excellent cross-ventilation to create wind speed that enables temperature reduction in shade. The bioclimatic design strategies intend to generate comfort zones within a range of 18-25°C with a relative humidity of 20-80%. The courtyards enable air exchange, and the evaluation of hotter air by convection. Finally, the solar protection provided by the green roof and eave overhang generate shaded areas that improve indoor comfort conditions.

The evaporation of water requires a larger amount of heat that reduces air temperature while increasing relative humidity, which is particularly beneficial in hot and dry climates for achieving indoor thermal comfort. This strategy is one of the oldest passive cooling techniques, used in traditional Persian and Egyptian architecture. Windcatchers were used to direct airflow through subterranean water in a qanat or indoor pools, bringing cool, humid air into the building. Courtyard houses also utilized this strategy with plants and pools. Roof ponds and water curtains are other passive techniques that cool spaces through evaporation.

Development Alternatives head office building in New Delhi is a showcase of traditional, environmentally efficient construction materials and systems that can be economically developed for low-energy mass production and adopted by the mainstream building industry, especially in developing countries. Air conditioning accounts for approximately 70% of the electricity used in new commercial office buildings in India. The most effective way to reduce electrical consumption is to reduce the cooling load and to use efficient cooling systems.

Exterior walls are designed for optimal passive thermal performance, minimizing indoor heat gain while allowing efficient dissipation of heat stored in the masonry. Vines trained on many facades shade the building to reduce heat gain. Roof surfaces are finished in white tile to reflect instead of absorbing thermal energy.

Shade, indirect or filtered daylight, the presence of greenery, and the sight and sound of water enhance the feeling of coolness. The three-story trickle fountain in the courtyard not only moderates the air temperature, but it is also a very effective suggestive device that supports the perception of comfort. The building also uses an innovative hybrid air conditioning system. In the hot dry season, the system uses direct and indirect evaporative cooling and then only in the humid season uses refrigerant cooling.

This strategy relies on heat transfer from a hotter body to a cooler one via long-wave radiation. In nocturnal radiation cooling systems, the entire building mass can lose heat to the night sky, cooling the indoor spaces. Cool roofs and cool surfaces made of high albedo materials can reflect direct sunlight during the day and increase heat loss at night.

White Canvas in Mauritania proposes a health center and school developed for the Mbera refugee camp in southeast Mauritania of more than 70,000 people, near the border with Mali. Foldable and easily erectable tent structures form the basic units for the school and health center facilities.

Phase Change Material (PCM) accumulators are used for air-conditioning, taking advantage of the temperature differential between day and night for creating livable and safe conditions without additional energy requirements – the colder air at night cools the hot air during the day. The PCM accumulator can be used in every building, independent of structure or function, in climates with relatively high diurnal temperature variations. Since it only uses the daily temperature variation for air conditioning, it does not require further energy for functioning. The use of this simple but effective technology in semi-desert or desert areas helps to improve living conditions in the camps, upholding the human dignity of the refugees and enhancing their chances for stability and self-reliance.

The exceptional heat capacity of the earth makes it an effective thermal mass that can balance temperatures throughout the year, providing cooling in summer and heating in winter through earth sheltering and ground source heat pumps. This strategy was used in traditional refrigerators or yakhchals to provide ice in summer for old cities in desert areas of Iran.

The Energy-Efficient Medical and Social Center in São Paulo, Brazil was designed with a focus on computer simulation to optimize aerodynamics, thermal behavior and natural lightning. The project uses an integrated geothermal pre-cooling strategy that brings available groundwater as cooling fluid to standard fan-coil units of conventional air conditioning systems. The adaptation of readily available equipment is highly economic and utilizes the groundwater that would otherwise be continuously pumped out of the site.

The building pre-shading is an important strategy adopted to decrease thermal loads and at the same time to optimize natural daylight conditions avoiding glare using perforated metal screen façades. At design, the energy saving from cooling and lighting was estimated at 80%.

Trees, shrubs, plants, and vegetation provide fresh air, reduce noise pollution, modulate air temperature and humidity, enhance biodiversity, and create beautiful and pleasant spaces. Vegetation absorbs solar radiation, provides shade, and releases moisture into the air through transpiration. Greening urban spaces and areas is beneficial for cooling spaces in arid and semi-arid climates. Architectural features of this strategy include courtyard gardens, green roofs, green walls, and bio walls.

Eco-Techno Park in Türkiye is a 85,000 square meter eco-park for sustainable research and technology that will promote small and middle-sized enterprises planned for OSTIM – one of Turkey’s largest formal industrial zones. The project, designed at the intersection of the constructed and the natural, aims to leave most of the site green, therefore the hill on the site is used for housing offices, conference and workshop spaces in terraces underneath the green texture. The building situated in the southern area of the site is designed as a landmark and is in close contact with the terrace structures along different levels. The terrace buildings offer a working environment intertwined with nature. Ortadogu Sanayi ve Ticaret Merkezi (OSTIM) incorporates various sustainable features in its design as well as measures for improved lighting, ventilation, heating, visual comfort and indoor air quality to ensure user satisfaction and efficacy.

The green roofs of the terrace buildings contribute to the isolation of the building and to improved air quality, also assisting to lower air temperatures and combat the heat island effect. In addition, this design creates a continuation of natural texture throughout the site.

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