Energy-Efficient buildings

Energy-Efficient buildings

Harnessing traditional architecture and modern science

If the techniques and the approach developed by TERI for energy-efficient buildings are applied to just 10% of the buildings constructed in cities every year, India can expect enough savings to light 20 million rural households. And if these numbers are mere projections, here is something more concrete: a conference facility including accommodation with a built-up area of 3000 square metres reduced its energy requirements from 280 kilowatts to 96 kilowatts by employing the principles of energy-efficient building design.

A self-contained island

When the Financial Express wrote about RETREAT (Resource-Efficient TERI Retreat for Environmental Awareness and Training), the paper described the facility as a self-contained island. The building employs an array of techniques – a 'combination of modern science and traditional knowledge' to quote former Prime Minister Vajpayee's words when he inaugurated the facility – including solar chimneys and earth air tunnels, fully integrated solar photovoltaic systems, water recycling, and a gasifier that uses firewood, dried leaves and twigs, and similar waste material to achieve not only considerable savings in energy consumption but also to reduce its 'ecological footprint'. Here are a few more details and highlights of the innovations.

South face of RETREAT showing solar water heaters and solar chimney
Space conditionining through earth air tunnels Space conditionining through earth air tunnels
The living filter: a bed of reed plants for treating waste water

  • Solar water heaters Twenty-four solar water-heating panels provide up to 2000 litres of hot (65 °C) water every day.
  • Integrated photovoltaic systems The energy captured by the photovoltaic panels is fed into a battery bank, which is the main source of power at night. A number of panels, each measuring 1.1 by 1.2 metres, are joined and form an integral part of the roof of the building. The panels can generate up to 10.7 kilowatts peak of energy, which is fed into a 900 ampere-hour/240 volt battery bank.
  • iomass gasifier Firewood, dried leaves and twigs, the stubble left in the field after a crop is harvested, and such other forms of biomass fuel the 50-kilowatt gasifier, which is the source of power for the building during the day. The gasifier runs a generator, the diesel requirements of which have been cut down to 30% after appropriate modifications; the rest of the fuel comes from the gasifier in the form of 'producer gas'. One unit of electricity produced needs 1 kilogram of biomass and 90 millilitre of diesel.
  • Subterranean air tunnels Effective insulation, shade provided by trees, and a network of underground earth air tunnels circulating cool subterranean air throughout the residential block ensure that the temperature in the complex remains more or less even all year round. The system has been augmented by adding chillers for dehumidification and additional cooling during rainy days.
  • Daylighting Specially designed skylights, energyefficient lights, and a sophisticated system of monitoring and controlling the consumption of electricity illuminate the complex. The conference rooms enjoy glare-free daylight through strategically placed skylights. A master control system switches off the lights automatically whenever it senses that daylight alone is enough to maintain the desired level of illumination. In the living rooms, strategically placed light points and specially designed swivels make it possible to use the light at a study table as well as for bedside reading.
  • Recycling waste waterA bed of reed plants (Phragmites) clarifies 5000 litres of water from the toilets and kitchen every day; the recycled water is used for irrigation. Sewage is collected initially in a settling tank (an Imhoff tank) that allows sludge to settle to the bottom. Part of the waste is decomposed at this stage by microbes. Then, the water is passed through a bed of soil, which also supports specially selected reeds well adapted to waterlogged soils. The roots of these plants act as living filters: they absorb and remove many of the toxic substances from waste water.

Applications/benefits

TERI can provide innovative solutions similar to those described here to promote energy efficiency in any building or group of buildings–old, new, or yet to be constructed.

Energy-efficient buildings require a higher investment of 29 500 rupees per square metre, as compared with 19 000 rupees per square metre for a non-energy efficient building, but offer substantial savings in energy consumption. For a 10 000-squaremetre hotel building with a life-expectancy of 30 years, an energy-efficient building will consume energy to the tune of 300 kWh/m2 [kilowatts per hour per square metre]) as compared with a non-energy-efficient building that will need 500 kWh/m2 of energy. The net present value is calculated to be positive at 8.1 million rupees, with an electricity tariff rate of 6 rupees/kWh, and a discount rate of 10%.

Replicating the success and spreading the message

RETREAT provides ample evidence that sustainable habitats can make not only ecological but also commercial sense, and TERI's advice is increasingly sought for a wide variety of projects ranging from single buildings to housing complexes. A partial list of clients includes

  • West Bengal Pollution Control Board (for its office building)
  • Indian Institute of Technology, Kanpur (for the biological sciences building)
  • National Thermal Power Corporation (office buildings in Simhadri and Koldam)
  • Manipur State Technology Council, Imphal
  • Bangalore International Airport.


North face of RETREAT: the conference block

The Green Business Centre building in Hyderabad – TERI was energy consultant to the project – received the prestigious platinum rating under the LEED rating system of the United States Green Building Council. LEED, or Leadership in Energy and Environmental Design, is a voluntary national standard that provides a framework for assessing building performance and meeting sustainability goals. TERI was responsible for ensuring maximum energy efficiency in the building through an appropriate building envelope and system interventions – and has now been retained by two more aspirants for the platinum rating: ITC Ltd (for its proposed Centre for Corporate Excellence in Gurgaon) and North Delhi Power Limited.

TERI is also committed to developing a rating system, to be ready by early 2005, for green buildings tailor-made to Indian conditions.

Energy saved is energy generated

  • Features of building design itself, such as appropriate orientation, insulation, and shading – what is referred to as 'passive solar architecture' – can reduce energy requirements by about 10% and day-lighting, control systems, and energy-efficient lamps can bring them down by another 25%.
  • A TERI study of 18 premier hotels in India found that energy conservation measures can lower electricity bills by 15% to 20%.