By Antoine Perrau
Environmental design in the humid tropics requires special consideration. This chapter is based on two case studies which attempt to develop a practical approach to including key elements of bio- climatic design in tropical regions.
Location: Reunion Island
Population 840,000 inhabitants
Area: 2512km 2
Geology: Volcanic island
Highest point: Mount des Neiges 3070m
Rainfall: Reunion holds all world records for precipitation between 12 hours and 15 days
Case Study 1: Malacca flores
Promoter: SIDR (Semi-Public Social Housing) Architects: Michel Reynaud / Antoine Perrau Environmental quality department: LEU Meeting City: Le Port
Altitude: 10 m leeward coast
Total floor area: 8950 m2
The project is located in a Development Zone and the objectives include: opening the city towards the sea, to reinvigorate the city centre, create a link between the periphery and centre of the community, and to implement the principles of sustainable development through a green master plan.
The projects location and surroundings were thus crucial to its success.
The site of a project and its concomitant micro climate is of particular importance in the tropics. Favourable conditions on site will impact the performance of buildings constructed there.
For instance the presence of trees plays a fundamental role in the areas micro-climate.
Our firm’s offices are in the centre of the island, allowing us to illustrate these differences.
During February, the month with the highest temperatures in the Southern Hemisphere, a temperature differential of 7 ° C was measured between the street and the inside of the office (without air conditioning). This is achieved in part, by planting buffers of vegetation such as grass and shrubs between the street and the building. The effect of the plants is to cool the air through evapotranspiration, and reduces the albedo effect by shading the concrete and other hard surfaces.
The role of plants in reducing the urban heat island effect has also been demonstrated in the city of Paris by researchers from Météo France. The diagram below illustrates the difference in temperature between the suburbs and the city center during a summer’s day, which was 4 ° C.
We therefore sought a favourable site for the project, and special effort was taken to re-vegetate surrounding buildings and find space on natural land.
The second step was to determine the most favourable orientation of the shading devices through computer simulations of sunscreen designs.
Parallel to this reflection, we verified the thermal comfort. It should be noted that the concept of comfort temperature is different from the temperature measured with a thermometer and is not absolute but depends on several parameters: humidity, air velocity, air temperature, the radiation
temperature of the walls, metabolism and clothing. One can evaluate the effect on internal comfort of a building as influenced by the first four factors mentioned above using the comfort graph developed by Givonni:
The graph demonstrates how essential it is to ensure natural ventilation, which is achieved through the porosity of the facades, and in this latitude, there should be a minimum porosity of 20% between two opposite facades.
Effective implementation of these interventions allows urban and architectural buildings to reduce their energy consumption by between 28 and 41 kWh / m2 / year. In fact spaces designed in this way provide thermal comfort without the need for air conditioning, even in the tropics.
Beyond these provisions, the specification proposes a number of other environmental features:
Implementation of solar hot water panels and photovoltaic roof panels
These panels are also used to shield the roof from high levels of solar radiation. 70% of the heat input comes through the roof, and so this element of the design should be treated with the utmost consideration and care.
This dual purpose of the solar devices can increase their efficiency and reduce overall cost. Increased use of wood to reduce the carbon footprint of the project Wood was specified for the structure of corridors, sidings, sunscreens and pergolas.
Grey water recycling
We used a filtration system with a settling tank and a filter zeolite vertical which provided regular contributions of water for irrigation.
Source: Continue reading to Case Study 2 in the Green Building Handbook Volume 4, pg 146
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