Quest to drive down energy consumption

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    KATHMANDU, MAY 14 –

    energy_matrixAmong the major consumers of energy is building industry (construction and operation) that also emits significant amount of greenhouse gases. Realising building’s role behind environmental crisis, architects are now in quest to find alternative design solutions to resolve the issues of resource depletion, global warming and energy crisis. Developed countries have already enforced ‘Green Building Codes’ to assess ecological sustainability of buildings. Many architects today are driven by the desire to get their high-end buildings Leadership in Energy and Environmental Design (LEED) certified! The LEED certification programme is the internationally recognised benchmark for the design, construction and operation of sustainable buildings. Others seek vernacular form and techniques, arguing that common builders managed to build using local materials without affecting the environment. Even in Nepal, large scale projects like high-rise apartments, hospital or shopping malls need to pass an environment impact assessment (EIA) to get legal construction permit.

    Vaastu shastra, an ancient treatise on urban planning and architecture states that for a design to be perfect, it should be in peace with nature. Only those materials should be used for building activities which can be softened by water, dried by air, burnt down by fire and cut by a sharp instrument. Ecological imbalance is the consequence of using materials that go beyond these criteria. Ironically, these days vaastu is being popularised through various media with different concerns.

    The traditional urbanscape and architecture of Kathmandu Valley presents sustainable ways of planning, design and construction. For centuries, towns in the valley were characterised by human settlements on fallow lands at hill top protected within agricultural farmlands. These farmlands extended from terraces cut into low gradient hill slopes to plain river basins at its lowest point. Early valley towns may be seen as precursor to Ebenezer Howard’s Garden city.

    However, with the advent of modern industrialisation, transportation, mass immigration, cultural degeneration towards rampant materialism and unplanned urbanisation led by weak governance the fertile farmlands have now turned into haphazard, hazardous settlements. The holy rivers have been defiled by discharge of sewer, excessive extraction of sand from river bed for construction purposes and loss of aquatic life.

    Traditional buildings were constructed using degradable materials like sundried bricks and timber. In a mud house, thicker wall of sundried bricks that heats slowly and releases the retained heat slowly perform better thermally. Proper sun shading devices were designed to allow only winter sun inside the house.

    By protecting the house from summer sun, orienting openings along wind direction and positioning them to create an effect of cross ventilation keeps it cool in summer. The slope roof was a natural response to drain away heavy monsoon rain. To protect exterior, the walls exposed special wedge shaped bricks called ‘dachhi appa’. When the houses had to be repaired or reconstructed, about 75 percent of the materials could be salvaged from the demolished rubble. Such wisely engineered houses whose materials could be reused or recycled are indeed ‘greener’ than any modern house.

    Sadly, modern people discarded these locally available materials considering them inferior. However, even a layperson knows that a mud house is cooler in summer and warmer in winter than concrete ones.

    Unlike the passive design of traditional houses, response of modern ones to the natural forces is quite poor. Their thinner wall of burnt brick or roof of reinforced concrete heats faster and cools faster. They must depend on active devices such as air conditioners, heaters or coolers to keep indoor living environment comfortable. Such dependence is detrimental to environment in the long run as energy consumption is higher in active devices besides release of gases and black carbon. Besides, repairing or reconstructing these houses is a difficult and expensive job as demolished rubble cannot be reused.

    Production of materials, their transportation and subsequent construction activities cause resource depletion. Expanding construction activity demands more production of materials such as burnt bricks, cement and reinforcements.

    For instance, excess brick production leads to depletion of clay converting arable land into disfigured landscape useless for future urban use. Since brick kilns are one of the major sources of black carbon that causes global warming, emits noxious gases like sulphurdioxide that pollute the environment, an alternative building material is highly warranted. When absolutely necessary, bricks may be produced by Vertical Shaft Brick Kiln (VSBK) that is more efficient and produces lesser pollutants. Consumption of bricks can be reduced by adapting to rat trap bond that saves 25 percent of bricks in comparison to English bond.

    Materials like adobe, rammed earth or compressed stabilised earth blocks (CSEB), eco bricks are some viable alternatives for constructing walls. Adobes are sundried clay blocks preferred in hot climates. Rammed earth walls are constructed in situ by manual or pneumatic ramming of material earth brought to desired shape with necessary formworks suitable for dry climate. CSEB are produced by mixing about five percent of cement to soil and compressed in manual machines called Auram or Cinvaram. These eco-friendly materials yield better thermal performance than burnt bricks leading to a more comfortable indoor environment.

    A model based on the CSEB technology can be observed at Institute of Engineering, Pulchowk where a green classroom is designed as a load bearing structure of CSEB set in mud mortar. The openings on the south bring enough daylight and solar radiations. For better insulation of interior environment, its timber window shutters use polycarbonate sheet instead of glass panes.

    The roof is constructed using compressed stabilised earth tiles that are set on a layer of bamboo mat which in turn is supported by timber truss and bamboo purlin. To overcome seismic loads, this classroom employs RCC horizontal ties at foundation, plinth, sill, lintel and roof levels and vertical ties on the corners and beside openings. This model with certain design alterations in response to specific site conditions has already been launched in many places like Bardiya, Banke and Kapilvastu.

    In order to achieve comfortable living environment for human activities buildings in response to topography, geology and climatology of place should receive enough day light, air flow and solar radiations. Then, choosing appropriate material and technology that exerts lesser pressure on the resources and put lesser impact on the environment can make a building green. Installing solar photovoltaic panels for electricity, harvesting water from rain or managing solid waste is a later step applicable to all buildings!

     

    (Pandey is a freelance architect and researcher)

    dipdutt.214@gmail.com

    Source : The Kathmandu Post