With increased industrialisation, use of technology in agriculture and urban irrigation, energy consumption is an ever expanding phenomenon. A study conducted by Energy Information Administration (EIA), US Department of Energy, indicates that there is a visible trend across the globe indicating that the growth rate in total energy consumption has been greater than the population growth rate.

In developed countries, the energy consumption growth rate is only marginally higher than the population growth rate. For example, in the US, energy consumption is projected to grow at 1.3 per cent, while the population growth rate is projected to grow at 0.8 per cent. In contrast, in developing countries like India, the population growth rate is expected to grow at 1.3 per cent, while the energy consumption rate is expected to grow at 4.3 per cent. This trend will strain the energy sector to a large extent.

The construction industry in India is growing at a rapid pace. Its rate of growth is 10 per cent as compared to a world average of 5.2 per cent. Hence, energy efficiency in the building sector assumes tremendous importance. Commercial buildings are among the major consumers of energy—the thirdlargest consumers of energy after industry and agriculture. Annually, buildings consume more than 20 per cent of the electricity used in India. The potential for energy savings is 40–50 per cent in buildings if energy efficiency measures are incorporated at the design stage.



For existing buildings, the potential can be as high as 20–25 per cent, which can be achieved by implementing housekeeping and retrofitting measures. The incremental cost incurred for achieving energy efficiency is 5–8 per cent vis-à-vis the conventional design cost and can have an attractive payback period of 2–4 years.

Typical Energy Consumption Pattern in Buildings In a typical building, air conditioning is the highest consumer of energy, followed by lighting and other miscellaneous equipment. Therefore, if the initial design considers energy efficiency measures in these areas, substantial energy savings can be realised.

Typical Energy-Saving Approach in Buildings
Orientation: This is the first step to achieve energy efficiency. The following measures can be adopted:

􀁘 Minimise exposure on the south and west

􀁘 Use simulation tools and techniques which can help in designing the orientation to minimise heat ingress and enhance energy efficiency.

Building Envelope: The following envelope measures can be considered in addition to using shading devices for window openings:

􀁘 Select high-performance glazing with low U-value, low Shading Coefficient and high VLT (Visual Light Transmittance)

􀁘 Insulate walls. The options for insulation materials include extruded polystyrene, expanded polystyrene (thermocol) and glass wool

􀁘 Brick walls with air cavities can also significantly reduce heat ingress

􀁘 Hollow blocks, fly-ash bricks and autoclaved aerated concrete (AAC) blocks are also good insulators

􀁘 Heat ingress through the roof can be as high as 12–15 per cent. Insulating roofs can substantially reduce heat ingress.



Equipment and Systems: A few guidelines could be kept in mind with respect to equipment and systems. These include:

􀁘 Selecting chillers with a high coefficient of performance (CoP)

􀁘 Installing variable frequency drives (VFD) for supply and return air fans and pumps

􀁘 Selecting high-efficiency cooling towers

􀁘 Using high-efficiency motors, transformers and pumps

􀁘 Installing heat recovery wheels

􀁘 Night purging with ambient air to flush out heat trapped within buildings during the day

􀁘 Adopting controls and building management systems for effective control

􀁘 Engaging a commissioning authority to ensure that savings are realised once the building becomes operational.

Lighting: The following tips for lighting may be considered in addition to designing the building such that it gets maximum day lighting:

􀁘 Overall lighting power density can be designed as less as 1.0 W/sq ft.

􀁘 Using daylight-cum-dimmer controls

􀁘 Installing occupancy sensors

􀁘 Selecting energy-efficient luminaires like CFL, T-5, LED, etc.

LEED India Rating System and Energy Efficiency
The LEED (Leadership in Energy and Environmental Design) green building rating system developed by the US Green Building Council is now recognised as an international rating system and is followed by more than 24 countries.

The LEED rating system has been indigenised by the Indian Green Building Council to suit the national context and priorities. A number of buildings in India have achieved energy efficiency in design by adopting the LEED India green building rating system.

A LEED-rated building consumes 30–50 per cent less energy than a conventional building. These buildings are designed to surpass the ASHRAE 90.1.2004 standards or ECBC (Energy Conservation Building Code).

The energy performances of three LEED Platinum-rated buildings have been monitored for about three years and the energy savings achieved are shown in Table-1.