Sustainable Buildings?

Sustainable Buildings?

There is no such thing as a sustainable building. A building is a part of a community, of a planet. We as a community need to adopt more sustainable ways of living. Only then will our buildings reflect how sustainable we are. However, there are definitely buildings that make a better use of natural resources than others. Building for a sustainable community is about making decisions to fulfil our needs and desires, while optimizing our use of natural resources.

Why? Virgin forests have long been gone. Pristine beaches are scarce. Plentiful corals and fishes are no longer. How to make the best use of what is left for us? This article seeks to provide alternate solutions to local design and construction according to three principles:

  • Smart use of construction materials.
  • Optimum comfort.
  • A moment of reflection.

The picture shows the Treasury Building in Port Louis which was originally completed around 1860 and renovated in 2003. Of all constructions, renovation makes the best use of available resources. In this case, no structural changes were made. The bricks and stones originally used for walls and vaulted ceilings were left exposed and all exterior joints were redone. Inside, an aluminium partition system was placed to organize different spaces. Mechanical, electrical and plumbing fixtures were added to fulfil modern needs.

Smart use of construction materials

The production of concrete, which is widely used in Mauritius, is problematic. Concrete is composed of cement, water, aggregates and admixtures. It is effectively man-made stone that can be poured into position. It has excellent strength, especially when reinforced with steel. However, the production of cement releases large quantities of carbon dioxide and requires a substantial amount of energy. Moreover, the constituents of nearly all the cement we use are quarried from non-renewable sources.

A good example of renewable material is snow. Igloos are snow houses built by Inuit people in Canada and Greenland. They might not be appropriate for Mauritius but they illustrate efficient use of construction materials. In addition to being highly renewable, snow is found in direct proximity of the structure. An equivalent to snow in Mauritius could be wood. If we found a way to plant a forest and manage it, we could harvest enough wood to build our houses. The Villa Astelia in Grand Baie is an example of local project using a wood frame. Concrete is only used for the floor slab. Dry vegetation used for thatch roofs is another highly renewable resource found locally.

In general, the lighter the material is, the less energy is used for assembling a building. However, ease of assembly also depends on the type of units used: bricks, blocks, planks or in liquid form. Assembling igloos does not require heavy machinery. Snow blocks are cut and stacked in a dome. Structures in Mauritius that have been assembled similarly are stone buildings. Stone and brick buildings are labour intensive, but might not require heavy machinery like concrete pouring does. Wood buildings can easily be assembled by skilled workers using saws, nails and screws.

After the igloo has fulfilled its function, the snow blocks return to their natural state. This cradle-to-cradle approach is one that is crucial, yet overlooked by most builders. Stone buildings are perfect example of structures that can be disassembled when needed, allowing the previously occupied site to be used by future generations. In Mauritius, a few stone buildings have successfully been relocated to more appropriate sites. It would be equally smart to design concrete units or bricks that can be disassembled for reuse. Alternatively, concrete can be crushed and reused as aggregate to make new concrete with the addition of more cement. However, this is not common practice in Mauritius. Here, concrete is crushed, but is recycled as larger aggregate to be used under new concrete slabs.

Alternatively, instead of being designed to be disassembled, a building can be designed to last a long time. Concrete is generally durable but many local concrete buildings already have cracks in them, some of which are not just surface cracks. It would be crucial to verify that minimum structural guidelines established in concrete construction are being followed by every builder for new constructions and renovations. Stone buildings are good examples of durable construction. Saint Francois d’Assise has been built in 1756 and is still proudly standing today. It has been renovated in 2005. The wooden slates have been replaced with metal roofing but structurally the building remains the same.

Optimum comfort

When talking about comfort, solar heat is the main challenge in Mauritius. In most houses the ground floor is at a comfortable temperature while the upper floor is not. That is because heat rises, but also because solar radiation directly hits the roof, which transmits a lot of the heat inside. One of the structures that is most effective at preventing solar heat from entering inside the building is the Institut Francais de Maurice’s double roof. A metal roof reflects some of the sun rays back up and provides some shade for exterior spaces. The rest of the heat is moved away by ventilation thanks to the large open air space underneath the metal roof. As a result, the regular concrete slab underneath the metal roof receives very little direct solar radiation, and consequently doesn’t transmit heat inside. Green roofs, reflective roof finishes and sloped roofs are other ways to minimise heat gain.

Thermal insulation contributes to keeping the inside of the building cool. Because concrete has very little thermal insulation capacity, other construction assemblies should be explored, especially when air conditioning is used. A lot of energy goes into cooling a building mechanically and if thermal insulation is not sufficient, heat rapidly finds its way back in. The Mauritius Commercial Bank has been designed with sufficient thermal insulation to receive BREEAM certification: 50mm thick extruded polystyrene insulation, a 300mm air gap and 8mm thick aluminium sandwich panels clad the concrete shell. In addition, the curtain walls are double glazed. Conditioned air is released from the bottom, closer to building occupants, with the help of a double floor structure. This enhances energy savings. In the residential sector, Maison de France and Villa Astelia have been designed with thermal insulation superior to that of concrete block walls.

Natural ventilation can often provide enough cooling to the whole building. It is most advantageous in Mauritius to place ventilation openings to let east trade winds in. Operable opening sizes can be calculated based on wind pressure and size of the building. LEED provides guidelines on how much opening surface is needed for sufficient ventilation. Natural ventilation has an advantage that air conditioning doesn’t. Many materials and finishes emit volatile organic compounds (VOCs) that are more or less dangerous to our health. Indoor air has been shown to be more polluted than outdoor air. If a building is often ventilated, VOCs are not such a critical issue.

LEED also suggests a minimum of glazed opening in each room for day lighting, depending on the size of the room and type of window. Clerestory windows, which are located closer to the ceiling, get more light than view windows, which are at eye level. Dome lights are also considered but not recommended because of excessive heat gain. Glazed surfaces, whether they are double-glazed, triple-glazed or argon filled, let more heat in than wall surfaces. Therefore, a balance has to be achieved between day lighting, ventilation and heat gain. Creole houses have for a long time been designed with large overhangs on all sides. Overhangs protect most glazed openings from solar heat gain but won’t protect the ones on the south west side. That direction is where solar heat is harshest in Mauritius, from mid-day to late in the evening. Any opening of any size in that direction should be avoided. When it is not possible, a mixture of exterior stores, trees and low shrubs can help. There are often many constraints that prevent a building from being oriented correctly. However, building orientation is one of the easiest and cost-effective ways to ensure optimum comfort for the occupants.

A moment of reflection

Following the guidelines above alone won’t endure that a building is as environmentally-friendly as it could be. No guideline, rating system or energy modelling program will ever completely replace human creativity. Consider the following points.

The giving tree.

There are plenty of sugar cane fields to build on in Mauritius. There are also numerous IRS, RES, HIS, private and public development in the pipeline. However, there are many advantages to leaving some of the space open for vegetation. Vegetated areas have been demonstrated to contribute to healing patients in hospitals. It would not be hard then to imagine a Zen garden as a preventive measure against stress-related diseases. Asphalt, which covers the majority of our roads and parking areas, has been shown to raise the temperature of surrounding areas by a few degrees. On the other hand, trees provide much needed shade. A fine example of building where existing trees bring life and excitement inside is the Institut Francais de Maurice in Rose Hill. The architect of this public facility has repeatedly insisted to keep most existing trees on site. Furthermore the construction team has gone out of its way to make this vision a reality. The result is a creative structure that becomes part of its natural environment.

Two birds with one stone.

In addition to having health benefits, open areas have the advantage of accommodating a wide range of activities. People camp, swim, play or simply rest on the beach. Most parks currently don’t have a very good reputation, but if well designed could be used more frequently for walking, jogging, cycling, playing, watching birds, gathering. The list goes on. There are many ways parks can be transformed into safe entertainment environments. Designing spaces to accommodate many uses is an eco-responsible decision because it prevents additional structures from being built.

About beauty.

Beauty might not seem important when talking about efficient design. But there is a reason why Mauritian patriots fight to preserve historical buildings. These buildings have a quality that triumphs over the test of time: character. Such examples of beautiful buildings are numerous in Mauritius. Eureka is a fine looking colonial house. The Church in Cap Malheureux, the Theatre and the Jummah Mosque in Port Louis are all great examples of beautiful public buildings. Designers and skilled workers have spent an enormous amount of time drawing and placing these planks and stones one by one, carving each detail. These buildings give Mauritius its distinct identity.

Other aspects of sustainability that haven’t been mentioned in this article include location and transportation to the building, water usage and waste disposal. These either relate to the subjects of smart urban planning or eco-responsible ways of living, which would each deserve their own article.

If you know of a building that is worth mentioning, please write to:

Author: Christel Sam - LEED Architect

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