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Realization Community
India / Tamil Nadu12.00,79.81
Client Name: Auroville Foundation
Project website: http://www.earth-auroville.com/realization_community_en.php
Project Description
Realization is a residential project of 17 apartments for 25 people in Auroville. Brought together by an acute housing shortage, many residents initiated a construction process coordinated by the Auroville Earth Institute. The project began as a movement in October 2007. Three blocks of apartments were built over the years and the project was completed in May 2012. The site plan was designed in accordance with micro-climatic aspects and judicious utilization of natural resources available onsite.
Building Details
Residence complex
New building project
3
1 BHK, 2 BHK
17
1,752 m²
900 m²
900 m²
INR 2,17,00,000
INR 14,500
2012
Project Team
Auroville Earth Institute
www.earth-auroville.com
n/a
n/a (engineering completed in-house)
Satprem Maïni
Climate Analysis
Realization Community is located in Auroville, an international township in the southern Indian state of Tamil Nadu, close to the city of Pondicherry. The climate is hot and humid, with the bulk of rain coming during the North-East Monsoon (October-December) and to a lesser degree during the South-West Monsoon (June-August). The town is located close to the sea, on a plateau. Significant reforestation efforts have created large swaths of forest throughout Auroville, which has significantly improved the micro-climate of the area during hot seasons. This allows passive ventilation strategies to be a very effective mode of cooling.
Design Approach
The layout of the buildings was done to preserve as much of the pre-existing vegetation as possible while taking advantage of prevailing wind direction for natural ventilation. The natural slope of the site allowed for a reduction in excavation for the foundations. All soil excavated was used for the production of Compressed Stabilized Earth Blocks (CSEB), the principle building material.
Realization apartments are multi-storied constructions with stabilized earth. The buildings were designed with earth a building material from foundations through roof: principally Stabilized Rammed Earth Foundations, Compressed Stabilized Earth Block (CSEB) for load-bearing walls, and CSEB vaulted roofing along with ferrocement channels to minimize the use of conventional roofing materials. Apartments were planned in accordance with the space allocation recommendations for Auroville, making ideal use of small spaces. Double height spaces were planned in many of the apartments to improve ventilation and natural light, while staggered floor plans were optimized for the prevailing winds.
Document
Special Feature
Windows, especially in double height spaces with proper orientation for natural lighting without excessive heat gain.
Rainwater from the roof is channeled to an underground cistern. This harvesting tank is cross-purposed as an earth cooling tunnel. Rainwater harvesting swales are incorporated into the landscape for maximum percolation rates and groundwater recharge, in a region where low water-table levels and salt water intrusion are chronic risks threatening access to potable water.
Several passive cooling strategies have been employed: 1. Insulation: Insulation on vaults for reduced interior heat gain. 2. Shading: Overhangs, set-back facades on vaulted spandrel walls, and tiered, elevated garden spaces shade the building envelop to reduce thermal gain and increase thermal comfort during the warm season. 3. Stack effect & Cross ventilation: Double story spaces for stack effect cooling are employed, with maximum cross ventilation to passively exhaust heat from buildings. Additionally, vaulted floor systems have cavities and ventilators which ventilate rising interior heat to the facades of the spandrel walls. 4. Cooling tunnel: An earth cooling tunnel cools exterior air through heat exchange by passing the air through ducts which run through the subsoil and underground rainwater harvesting tank. 5. Hygrothermal cooling: Stabilized earth additionally has a hygrothermal cooling effect, as the active clay particles cause an evaporative cooling effect within the wall when exterior temperatures rise.
Virtually all buildings systems are equally as cost-effective as they are low in environmental impact: A key feature of earthen construction is that - as a labour- intensive construction technique - a high percentage of construction cost is invested into local economies of production and construction, as opposed to imported industrial building materials. In the case of Realization, approximately 65% of the cost of construction was for labour; this is roughly the opposite of cement-based building technologies (in which generally 60-65% of construction is invested in material).
The most passive approach of this building system is construction which minimizes initial embodied energy. Maximum use of raw soil (already a zero to very low EE material), further excavated from the site, dramatically reduces the initial embodied energy and carbon footprint of the construction. Thus, circular ecology principles govern the overall technical design. The soil characteristics (selection of the site itself in response to the quality of available soil) allows for a minimum amount of cement stabilization (5%) to produce load-bearing block with sufficient strength for up to 4 stories. Analysis has showed that the initial embodied energy amounted to less than 1/4th that of a conventional building system (RCC frame and country fired brick infill system).
Building Material
Load-bearing masonry of Rammed Earth and Compressed Stabilized Earth Block
Stabilized Rammed Earth Foundations (5% cement stabilization)
Compressed Stabilized Earth Block (CSEB) masonry (5% cement stabilization)
Wooden frames made from trees cut on site or downed during the 2012 Cyclone Thani (which felled up to 60% of trees in Auroville)
Ceramic Tile
Lime Stabilized Earth plasters
CSEB masonry vaults (principle roofing); ferrocement channels (secondary roofing system) Load bearing structural masonry vaults were built with CSEB. As a compression-only roofing system, this allows standard, high embodied energy RCC roofing to be replaced with stabilized earth. No steel is required in a compression-only vault (only an optimized amount of steel in springer beams and tension ties). All structural calculation was done in-house at the Auroville Earth Institute.
The extremely low initial embodied energy of these building materials tremendously offset the overall expected lifetime embodied energy and emissions of the buildings. While a comprehensive life-cycle analysis was not done, the total embodied energy and carbon emissions of the buildings' construction were fastidiously counted, implementing an inventory of carbon and energy for the Indian subcontinent which was developed by AVEI.
Energy systems
Natural lighting and energy-efficient bulbs
Energy-efficient bulbs
According to the preferences of the occupant
According to the preferences of the occupant (with intended aim of zero air conditioning)
None
Photovoltaics were integrated into the electrical infrastructure but not implemented on account of cost.
Lessons Learned
The project initially started as a participatory construction project aiming at low construction costs. However, final beneficiaries were not sufficiently engaged into the process, and the volunteer group eventually dwindled and had to be replaced by paid workers when motivation ran out. This led to higher final construction costs than initially estimated. However, the design and execution proved effective, and the Realization apartments have demonstrated excellent responsiveness to the local climate in terms of indoor living environment and durability.
Extensive post-occupancy research has been done to assess users' acceptance of earthen buildings (ongoing doctoral research by Nourredine Kebali, Ecole Polytechnique d’Architecture et d’Urbanisme d’Alger, Algeria, topic: “Satisfaction level of people living in earthen houses”).