“NOMINATED BY THE AGHA KHAN AWARDS TO ENTER THE PRESTIGIOUS AGHA KHAN AWARDS FOR ARCHITECTURE”
Iran is a dry country. Precipitation in the Iranian plateau is less than 1/3 of world average while the evaporation is more than 3 times world average. Life has long been built on a delicate balance of ‘sustainable consumption’ of the limited water resources and a self-controlled population. Now, this balance is about to be upset by the global warming which has resulted in less and less rainfall causing creation of ‘salt marshes’ in place of major lakes and rivers ‘lake Urmia’ or ’Zayandeh-rud river’ and by the growing size of population as well as exhausting underground fresh water basins. Same story is happening in other countries too, albeit at a different pace and we may not be very far from witnessing big forced displacement of people and uncontrolled environmental-related immigration.
Facing the above scenario BMDesign Studios focused on a design strategy to improve ‘resiliency’ of the current system as well as finding a way to use global warming to people’s advantage. To introduce a ‘safe to fail’ measure into the system, BMDesign Studios came up with the idea of the “concave roofs”, a designed redundancy in the water supply through efficiently harvesting precipitation in the forms of “rainwater” and “morning dew” in the hot and dry habitats of the South of Iran where they are located at the edge of desert but also get to enjoy a tangible high relative humidity from the adjacent water body the Persian gulf. At 60% efficiency we shall be able to collect 28 cubic meter of clean rainwater and more of morning dew.
Objectives of the project:
- We wanted to see if we can use changes caused by the global warming to people’s benefit where it hit them the hardest.
- We wanted to find a way for the buildings in hot semi humid areas with minimum rainfall, to be able to produce their own potable water from more unconventional sources and to produce it from an infinitive source (here the atmosphere) rather than from water reservoirs that have a finite consumption capacity and already stressed.
- We also wanted our solution to be aesthetically pleasing and to be able to build a powerful sense of place and a distinctive character both at the smallest habitable unit level (a building) and at an urban level (a metropolis). This kind of using a unique architecture for creating a sustainable living machine (as Le Corbusier call it) is not without precedent in Iran. Famous ubiquitous wind towers of the city of Yazd, not only cool the buildings naturally but also make the distinctive character of the city.
- Less carbon footprint through sustainable design, due to using less energy for cooling in summer by employing a double layered roof system. The dishes, the first layer, cut direct sunlight from hitting the main roofs (second layer) but allow outdoor breeze to move between the two layers.
- Raise awareness toward water shortage and global warming by highlighting the tech and Rain-Dew harvesting structures.
- Building a strong character and sense of place through proposing the bowl shaped roof that is capable to be repeated all over city roofs.
- With a Concave Roof (bowl shaped structures) and a rough calculation, we should be able to collect 106 cubic meter of clean rainwater from 923 square meter of concave roof area and 193mm of annual rainfall in total. The efficiency is considered to be around 60% according to Brad Lancaster calculations for RWH in dry-lands.
106 (RAIN HARVEST in m3) = 923 (Catchment Area in m2) x 0/193 (Rainfall Depth in m) x 0/60 (Conversion Factor)
Also all classrooms, offices and libraries are designed in a sunken courtyard, like what we see in the traditional architecture of arid zone cities like Yazd and Nain in the heart of Iranian plateau. Environmental advantage of a Sunken Courtyard is in its ability to trap cold air at night and thus reduce energy consumption for cooling indoors during the day. All building openings are recessed to further control the sunlight indoors and consequently the temperature.
Date palms added to provide more shade over the concave roof and to provide visual structure and enclosure as well as bearing dates.
1-Concave roofs/ Rain harvesting dishes
- Rain harvest & providing shade
Rain drops hit the earth at an incredible speed of 10m/s and break up to droplets. In a heavy rainfall these tiny droplets integrate and make a flow of water on the surface. In light rainfalls these droplets eventually evaporate back to atmosphere before they can make a flow but by employing a very steep sloped roof in the shape of a dish or bowl we can help these droplets to run and integrate into bigger drops and be collected.
These big dishes (the outer shell) provides shade for the main roof below while letting the air to freely move and cool both roofs off.
- Dew harvest
In Namib desert – Fog-Basking Beetles gets their water source from the fog by the way of condensation. The dew droplets run over their smooth posterior and they drink it. The cold smooth surface of concave dishes on roof do the same, they help the dew that forms on their surface to flow down the dishes and be collected.
2- Courtyard building
- Trapping the cold air
Courtyard buildings are very common in desert architecture because they are excellent in trapping the cold air. In our project we designed a sunken courtyard building to trap desert’s cold air at nights, reducing the dish’s temperature during the night that will help more dew forms on the inner surface of the dishes and more rapidly. Cold night’s sky also will make the dishes cold by the way of radiant cooling.
to bring this design into reality there are some challenges to meet:
- Global warming is causing Lower rainfall but higher relative humidity
- Less rainfall means that we have to find new ways to collect smaller amounts of rain drops that pours on a surface but does not flow will evaporate eventually. On the other hand, higher relative humidity in places where desert meets water bodies means higher opportunity to collect dew where the desert nights are cold.
- Technological challenges
- We wanted to know which material is best for our rain and dew harvesting dishes? Several materials have been considered for this purpose. Metal was one of the initial choices because of its very low ‘Specific Heat’ which makes it a very good choice to collect dew, because it gets cool fast as a result of the radiant cooling effect, but the downside is that it also gets really hot during the day which makes it a bad choice for collecting rainfall. In the end, a coated impermeable fabric-such as the ones used for tensile structures- has been chosen because not only does it provide a smooth surface that is excellent for collecting rain it also gets cold enough in the morning hours to accelerate formation of dew by the way of condensation.
- Structural challenges to fix the bowls above the roof.
- ECONOMIC AND SOCIAL CHALLENGES
- High initial cost
- Many do not believe in rain harvesting at all, even though it’s proven and practiced worldwide.
ARCHITECTURE FIRM: BMDESIGN STUDIOS, BABAK MOSTOFI SADRI
OFFICE WEBSITE: WWW.BMDESIGNSTUDIOS.COM
COMPLETION YEAR: IDEA
BUILT AREA: 550 SQUARE METERS
PROJECT LOCATION: SOUTH OF IRAN
TYPE: PUBLIC SCHOOL
LEAD DESIGNER: BABAK MOSTOFI SADRI
DESIGN TEAM: DENA BAKHTIARI, NAZANIN ESFAHANIAN, NEGAR NAGHIBSADAT
MODEL: DENA BAKHTIARI
STRUCTURAL ENGINEER: SINA ROSTAMI