As we embark on rapid urbanisation, the unprecedented upsurge in new construction will be accompanied by a manifold increase in the demand for electricity. Poor energy performance appreciably increases the operating costs of a building, and the impending situation calls for designing buildings of the future by incorporating energy-efficient features and sustainable practices. The construction cost of energy-efficient buildings may be higher, but they turn out to be cheaper in the long run as they consume less than half the energy than conventional buildings.
The cost-benefit ratio of an energy efficiency measure works best in new constructions. For instance, creating a provision for energy-efficient glazing or air-conditioning in an under-construction building works out to be much cheaper than retrofitting the same components in an existing building. A study conducted by TERI to investigate the financial feasibility of green building investments by evaluating the economic impact of incorporating energy-efficiency strategies in commercial buildings revealed that the incremental capital investment for a green building is recovered with paybacks of one-to-three years.
Besides a zero-energy building design and low-energy building materials, green buildings typically involve components like energy-efficient equipment and integration of renewable energy technologies for various applications. While low-energy buildings require little energy for space heating/cooling, efficient power supply depends on a robust transmission infrastructure, which is characterised by smart grid applications like Supervisory Control and Data Acquisition. A smart grid entails a variety of operational and energy efficiency measures like smart meters and smart appliances.
Whereas conventional buildings rely on multiple systems for lighting, heating and other functions with each one operating independently of the other, green buildings improve energy efficiency by connecting these systems, thus leading to an appreciable reduction in operating costs. An energy-efficient building balances all aspects of energy use in a building like lighting, spaceconditioning and ventilation by providing an optimised mix of passive solar design strategies, energy- efficient equipment and renewable energy.
While state-of-the-art engineering and architectural techniques not only add to the strength of the structures but also reduce maintenance charges, optimisation of space design—characterised by features like large window openings for natural lighting and cross-ventilation—enhances the flow of energy. The linear design, for instance, significantly brings down the maintenance cost by aligning water supply pipes, sewerage lines, electrical conduits and HVAC ducts in a straight line with a single duct system put to multiple uses.
Even simple design elements such as window location and sunshades can go a long way in conserving energy. Installed at the top of windows and doors, sunshades can protect the building from overheating during summers and keep it warm during winters. Aligning buildings in such a way that sunrays do not fall on them perpendicularly can also reduce the use of air-conditioners, and so can insulated windows, walls and roofs. Insulation helps reduce heat gain into and heat loss from a building. Insulation materials like mineral wool and fly ash-based aerated concrete blocks can be used in roofs and walls to reduce heat transfer.
The most distinctive architectural feature of an energy-efficient building is its compactness, the ratio of its surface area to its volume. The lower the ratio, the lesser the heat gain. Ideal for hot-dry climates, compact buildings gain less heat during daytime and lose less heat at night. Another important design aspect of a green building is ventilation, wherein a mechanical system with heat recovery can be used so that hot air leaving the building warms the cooler air coming in. A similar device called enthalpy wheel can be used to recover cooled air from inside and uses the coolness of this spent air to cool fresh air from outside. The process dehumidifies the air from outside. This is a cost-efficient way to improve indoor air quality and reduce the energy consumed by ACs.
Likewise, we have passive heating techniques like direct gain method for cold climatic zones, where sunlight is permitted into habitable spaces through an opening, allowing it to directly strike and heat the floor, walls or other internal objects. These, in turn, heat the air within the room. Double glazed windows are aligned to receive maximum sunlight in winter. During the night, these windows act as insulating curtains and prevent heat loss.
Another crucial element of a green building is efficient power supply, characterised by energy-efficient appliances used for lighting, cooling and heating, which can help save up to 40 percent on electricity bills. Apart from energy-efficient ACs and lighting appliances like LED bulbs and CFLs, applications like daylight-controlled lighting systems with sensors which switch off the lights during the day and switch them on at sunset are getting increasingly popular, and so are occupancy sensors which turn on the lighting system only when they sense people in the room.
However, to make our buildings green in the true sense, we need to integrate them with solar systems and feed the surplus electricity generated through solar power into a smart grid network. A domestic solar water heater can easily replace a 2-kW electric geyser, saving up to 1,500 units of electricity annually. PV systems, on the other hand, can be built-in at the construction stage for new buildings and retrofitted on existing buildings as well to save on inflated power bills.
But all said and done, many new buildings in India continue to be designed in utter disregard for energy optimisation, resulting in a substantial loss of energy and financial resources. The situation calls for regulation of efficiency measures for buildings. Spelling out the guidelines for energy-efficient buildings, the Bureau of Energy Efficiency had introduced the Energy Conservation Building Code (ECBC) for new commercial buildings in May 2007. While the target for the 12th plan is to make 75 percent of all new commercial buildings ECBC-compliant, it is up to state governments to enforce the code after modifying it as per their requirements. So far, only seven states have adopted ECBC.
Though India aims to reduce the emissions intensity of its GDP by 33–35 percent by 2030 from the 2005 levels, it is easier said than done. We have a long way to go as the stock of energy-efficient buildings comprises just 1 per cent of the total building stock. It is projected that by 2050, India will see a 400 percent escalation in floor area. But energy efficiency in the residential segment has not been a priority. We cannot achieve a significant scale unless we standardise efficiency measures for residential buildings, which make up for 75 percent of India’s construction market. Let’s put things on fast track by overcoming the financial barriers hindering the adoption of energy efficiency measures for buildings through relaxations in duty, incentives, tax benefits and attractive financing schemes.