Due to the extremely high temperature of the Arid/Desert climate zone, during extreme heat stress, temperature in Abu Dhabi could reach up to 46°C. This makes interior cooling inevitable. However, while the interior spaces are being cooled down, heat is being exhausted into the ambient air. In combination with the cityscape where reflective surfaces and hardscape dominate the built environment, urban heat island accumulates. It crucially increases outdoor temperature making public spaces unbearable.
To tackle this issue measures to increase green spaces in the UAE have been promoted in recent years, however it also causes side effects. Researches have shown as UAE has the highest water consumption in the world! And 80% of its consumption has been used in the greening projects. If no alternative strategy is introduced this paradoxical cycle would never cease.
Hexhale is a pod prototype for public space operating with passive ventilation system through evaporative cooling with self-sufficient greywater treatment loop.
Part 1: Framework
In order to alleviate the situation “(H)exhale” has been proposed. “(H)exhale” is developed as a tool and design strategy to improve the quality of public spaces both in terms of function and comfort, while self sufficiency is also thoroughly taken into consideration.The implementation of the “(H)exhale” system would transform the public spaces into a comfortable outdoor space despite the high heat level of the desert climate. Additionally, to achieve self-sufficiency the space would also function as a grey water treatment park. Through the means of natural filtration systems, grey water from surrounding areas will be treated and simultaneously used in the cooling process. Furthermore, due to the high solar yield, Photovoltaic systems are also integrated as a part of the self-sufficient strategy to provide electricity for the system operation.
Part 2: Design Strategy
To efficiently create a strategy in transforming the public space with (H)exhale, the site context has been studied. Solar radiation along with wind analysis had been conducted. This allows modules such as Module A the Wind tower to be placed effectively. Furthermore, design alternatives to be generated in relation to the constraints effecting the site such as solar radiation, shading area, public space, air circulation and cost.
Isometric Drawing of the system operation.
Part 3: System Module and Passive cooling strategies
Passive cooling strategies which are suitable for the desert climate such as shading, thermal mass, permaculture planting, evaporative cooling, and ventilation have been incorporated with the vernacular strategy and implemented with a modular approach. “(H)exhale” consists of 5 modules of prefabricated rammed earth. They are strategically positioned to create a courtyard space. At the same time, the interconnected module would also efficiently serve as a cooling and water treatment system.
Due to the dry ambient air of Abu Dhabi, the evaporative cooling strategy is favourable. The principle of evaporative cooling is making air cool by increasing its water vapour content. As water is evaporated, sensible heat is being converted into latent heat, which resulted in the reduction of ambient temperature. Considering 100% wet bulb efficiency, direct evaporative cooling would allow the temperature to be as low as its wet-bulb temperature. However, according to the psychrometric chart, wet bulb effectiveness of 60-70% would be sufficient to provide thermal comfort to space.
Learning from the Courtyard
Courtyard is one of the distinguish element of architecture in desert areas. The vernacular approach serves as a public space while provide cooling through water body, shading, and thermal mass. Using courtyard spaces as precedent, the modular system is strategically positioned to create a courtyard space which shapes both ventilation and shading.
 Landscaping with native plants in the UAE: A review increasing the outdoor temperature making public spaces unbearable.