page_title: Retrofitting Building M: University of Reunion Island, France
section_title: Passive design systems
hierarchical_section_title: Retrofitting Building M: University of Reunion Island, France / Passive design systems
caption_attribution_description: English: Principles of passive design in summer and in winter
context_page_description: Building M is located on Reunion Island on the outskirts of the town of Le Tampon at a high altitude and benefits from a tropical climate. From 1972 to 1991, Building M housed an army school. In 1994, the South Campus of the University of Reunion Island was created and the army buildings were converted into classrooms for the future students.
  In order to meet the local needs in terms of energy self-sufficiency and building performance, the University of Reunion Island has opened a new department at ESIROI its Graduate Engineering School, called The Department of Construction & Energy, to which Building M was assigned.
  Like the other timeworn buildings, Building M does not respect the basic bioclimatic principles, such as natural cross ventilation and daylighting. Reunion Island has to face several issues. Indeed, the first major issue is that Reunion has one of the more polluting energies of the world with 820g of CO2 emitted for 1 kWh produced.
  Given the increase in demographic trends, the island is already facing a growing demand for energy according to a recent study.
context_section_description: A huge range of innovative systems will be set up in Building M, especially in terms of thermal comfort and natural daylighting. Firstly, this retrofit will be based on the local climate taking the surroundings into account and creating a harmonious relationship between the building and its immediate environment.  As a result, it is essential to collect data concerning the local weather (Figure 5).
  As shown in Figure 5, two seasons can be observed: the summer period with outdoor temperatures that range from 13 °C to 30 °C and the winter with temperatures that vary from 8 °C to 22 °C.
  Secondly, the purpose is to find a solution so as to warm the building in winter and protect it from the sun in summer, using passive solar systems that are incorporated into the building, as well as taking environmental resources such as wind, sun and vegetation into consideration.
  To cope with summer temperatures, interior and exterior light shelves associated with solar protection will be set up in the building. These systems will be sized using engineering tools such as the sun path diagram of Reunion Island as well as different software tools which will establish the design and evaluation of the most satisfactory option. According to the results obtained, the most appropriate solution consists in creating a specific system on each side of the building. Thanks to this design, natural daylighting will be provided with the exterior light shelves in summer, whereas in winter, when the solar height is lower, the interior light shelves will play this key role.
  In addition, a patio will be designed so as to provide natural cross ventilation. A chimney principle has been chosen to create the ventilation phenomenon. In order to minimize the solar heat gain, an external wooden cladding consisting of 6 cm of insulation material, will be installed.
  Moreover, large openable windows with exterior and interior louvres will optimize natural cross ventilation as illustrated in Figure 6.
  In the wintertime, the solar protection will let the sun stream through the windows and heat the classroom by increasing the ambient temperature. Furthermore, with an adequate insulation system applied in particular on the roof and the walls, a temperature included in the comfort zone of the occupants should be reached.
  It must be pinpointed that this thermal comfort depends on six parameters: clothing, metabolism (linked to the level of activity), the wall temperature, the air temperature, the relative humidity and the wind speed.  
  In tropical regions, the Givoni comfort diagram is a suitable tool for the assessment of thermal comfort. The Givoni comfort chart is based on the expected indoor temperature rather than outdoor conditions. Using Givoni’s comfort diagram on a psychometric chart, it is possible to predict the different operational periods for natural ventilation and ceiling fans. Three comfort zones can be defined according to the wind speed (Figure 7).
  Thanks to passive technologies such as the skylights, the light shelves and the patio, visual and thermal comfort objectives should be attained.
  Due to the rugged relief of the island, the region of “Le Tampon” is relatively well protected from strong winds. Therefore, the building does not require specific protection from this factor. In addition, the main facades of the building are positioned towards the north-east and the south-west. Consequently, the orientation of the building is quite adequate to benefit from thermal breezes.
  One of the greatest challenges of the retrofit was to find a new approach in order to provide natural daylighting without significant costs. The solution chosen by the designer is to create skylights with two specific functions. Indeed, they will let the light come through to the classrooms as well as creating an upper ventilation system.
caption: Figure 6: Principles of passive design in summer and in winter (Architect's model)
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