The potential beneficiaries of this guide include building owners, designers, energy modelers, users, building developers, building facility managers and operators, building product manufacturers, and other stakeholders. A wide diversity of building costs, services, and comfort levels requires application-specific design for optimizing energy efficiency. A small portion of the office stock consists of unconditioned, lower-cost indigenous buildings; with arguably acceptable low-energy solutions for comfort levels adapted to regional and climatic considerations. The bulk of the existing stock consists of mass-produced business-as-usual office buildings with a typically lower level of services , or fitted with ad hoc air conditioning to provide ostensibly higher level of services. However, the BAU trend is toward the construction of new, air-conditioned, sophisticated buildings that provide international levels of service. With the exponential increase in the floor space of this type of buildings, the projected growth in building cooling demand will be explosive.Several building physical systems have been adopted from western applications without accounting for the regional, climatic, cultural, and economic context. On the other hand, several region specific systems already exist in indigenous buildings that are able to offer higher performance for minimal cost, but the methods used to design such buildings are rapidly disappearing,plastic pots for seedlings because of a lack of visible documentation and analysis of the techniques.
India needs appropriate localization of energy-efficient technologies to meet the needs of various regions, with respect to weather, standards, materials, construction, and technological maturity . Buildings in India were traditionally built with high thermal mass and used natural ventilation as their principal ventilation and cooling strategy. However, contemporary office buildings are energy-intensive, increasingly being designed as aluminum and glass mid- to high- rise towers . Their construction uses resource-intensive materials, and their processes and operations require a high level of fossil fuel use. A large share of existing and upcoming Indian office space caters to high-density of occupancy and multiple shift operations. Whereas the average for U.S. government offices is 20 m2 /occupant and for US private sector offices is 30 m2 /occupant, Indian offices have a typical density of 5–10 m2 /occupant. Business Processing Office spaces have three-shift hot seats—a situation that while conserving space because of its multiple usage also leads to considerably higher EPI levels. . Moreover, with the increased demand for commercial office spaces from multinationals and IT hubs, and the current privileges being accorded to Special Economic Zones , the trend is toward larger buildings with international standards of conditioned spaces, dramatically increasing the energy footprint of Indian offices .Building energy consumption in India has seen an increase from 14% of total energy consumption in the 1970s to nearly 33% in 2004-2005.
The gross built-up area added to commercial and residential spaces was about 40.8 million square meters in 2004-05, which is about 1% of annual average constructed floor area around the world and the trends show a sustained growth of 10% over the coming years, 4 highlighting the pace at which the energy demand in the building sector is expected to rise in India. In 2004– 2005, the total commercial stock floor space was ~516 million m2 and the average EPI across the entire commercial building stock was ~61 kWh/m2 /year. Compare this to just five years later in 2010, when the total commercial stock floor space was ~660 million m2 and the average EPI across the entire commercial building stock almost tripled to 202 kWh/m2 /year . Energy use in the commercial sector is indeed exploding, not just due to the burgeoning of the Indian commercial sector- India is expected to triple its building stock by 2030 , but also through the increase in service-level requirements and intensity of energy use. Thus there are two intertwined effects: an increase in total building area and an increase in the EPI. According to India’s Bureau of Energy Efficiency , electricity consumption in the commercial sector is rising at double the rate of the average electricity growth rate of 5%–6% in the economy. To deliver a sustained rate of 8% to 9% through 2031-32 and to meet life time energy needs of all citizens, India would need to increase its primary energy supply by 3 to 4 times and electricity generation capacity about 6 times.
According to UNEP, approximately 80%–90% of the energy a building uses during its entire life cycle is consumed for heating, cooling, lighting, and other appliances. The remaining 10%–20% is consumed during the construction, material manufacturing, and demolition phases. 6 To manage and conserve the nation’s energy, it is imperative to aggressively manage building energy efficiency in each commercial building being designed and operated in India. By increasing energy efficiency in buildings and other sectors such as agriculture, transportation, and appliances, it is estimated that the total Indian power demand can be reduced by as much as 25% by 2030. 7 To this end, the best practices outlined below identify processes and strategies to boost the energy efficiency in buildings, while also focusing on cost efficiency and occupant comfort.Just as no two buildings are identical, no two owners will undertake the same energy management program. It is also improbable to include all the listed best practices into one building, since some of them will conflict with each other. The practices are presented individually; however, they should not be thought of as an “a la carte” menu of options. Rather, designers and engineers, developers, and tenants need to work together to capitalize on the synergies between systems . From the demand side, this means implementing a suite of measures that reduce internal loads as well as external heat gains . Once the demand load is reduced, improve systems efficiency. Finally, improve plant design. This is illustrated through the Best Practice strategies and Data Points in this guide. The supply side can then add value by provision of renewables, waste heat sources, and other measures that are beyond this guide’s scope .The guide illustrates innovative strategies and technologies across office buildings in India. It focuses on cross-cutting, whole-building strategies, as well as systematic measures for each load type . Tables of quantitative metrics allow for apples to-apples comparisons, and provide hard targets. The “standard” data in the tables reference numbers from ECO III bench marking or the National Building Code of India. This “standard” data is representative of the median or 50th percentile of commercial buildings in India. For “better” practice data,blueberries container either the Energy Conservation Building Code or better performing buildings have been referenced, and are representative of the top quartile. For the “best” practice data , the top 5th percentile, or best-in-class buildings have been referenced. To design and operate an energy-efficient building, focus on the energy performance based on modeled or monitored data, analyze what end uses are causing the largest consumption/waste, and apply a whole-building process to tackle the waste. For instance, peak demand in high-end commercial buildings is typically dominated by energy for air conditioning. However, for IT operations, the consumption pattern is different. In the latter, cooling and equipment plug loads are almost equally dominant loads.
The equipment plug load is mostly comprised of uninterrupted power supply load from IT services and computers, and a smaller load is from raw power for elevators and miscellaneous equipment. Figure 8 shows typical energy consumption end-use pies — energy conservation measures need to specifically target these end uses. By doing so, one can tap into a huge potential for financial savings through strategic energy management. However, a utility bill does not provide enough information to mine this potential: metering and monitoring at an end-use level is necessary to understand and interpret the data at the necessary level of granularity. Energy represents 30% of operating expenses in a typical office building; this is the single largest and most manageable operating expense in offices. As a data point, in the United States, a 30% reduction in energy consumption can lower operating costs by $25,000 per year for every 5,000 square meters8 of office space. Another study of a national sample of US buildings has revealed that buildings with a “green rating” command on an average 3% higher rent and 16% higher selling price. 9 Whether in the US or India, improvements to energy efficiency can often be attained through no-cost or low cost ECMs that lower the first costs of construction and equipment. Optimizing building loads can lead to lower first costs and operating costs. By targeting low-hanging fruit through early-stage ECMs, the first costs saved through these can be applied toward more expensive technology solutions like high-quality glazing or sensors that can further the energy and cost benefits later in the building life cycle. Hence, it is important to decide which measures to prioritize initially, and then what to cross-subsidize eventually. For example, if one is able to save costs by reducing the number of lighting fixtures and taking advantage of high daylight levels in a space, then those savings can be used to install daylight sensors. The latter can provide a large cost benefit with a relatively short payback time by driving down the operational hours for artificial lighting. The ECMs at the whole building level using systems integration can greatly benefit the EPI of a building. Table 1 shows whole building energy use metrics, using Standard , Better , and Best Practices at the whole building level.Optimizing day lighting and lighting can provide better views and improve the visual acuity of the occupants. Well-designed mechanical systems can improve indoor air quality while reducing initial equipment and operating energy costs. Workplace productivity can increase by providing individual controls, and with direct access to daylight. Given that the bulk of working time is spent indoors, a better indoor environment can boost worker performance and reduce sick leave that could equate to monetary benefits to businesses.Displacement ventilationdelivers the air at low speeds using the principle of air stratification. Here, air is delivered at close to floor level for primarily conditioning the occupied volume and extracted at the ceiling height rather than conditioning the unoccupied higher volume first. Well designed DV systems provide better indoor air quality since the air in the occupied zone is generally fresher than that for mixing ventilation. There are no perceived air drafts. Any released pollutants rise rapidly to above the occupied zone. Large cooling energy savings are possible, as it uses a higher supply air temperature at 18°C, which also increases the efficiency of mechanical cooling equipment and lowers equipment requirements. Underfloor Air Distributiontechnology uses the underfloor plenum beneath a raised floor to provide conditioned air through floor diffusers directly to the occupied zone. A thoughtful design can overcome the usually cited challenges of uneven floor surfaces, difficulty in providing added airflow to the perimeter of the building, and perceived control difficulty. The advantages of a well-designed UFAD system are: improved thermal comfort, occupant satisfaction, ventilation efficiency and indoor air quality, reduced energy use and the potential for reduced floor-to-floor height in new construction. Radiant Cooling works on the principle that water can store 3,400 times more thermal energy per unit volume than air. It offers the potential to reduce cooling energy consumption and peak cooling loads when coupled with building thermal mass. Some radiant systems circulate cool water in dedicated panels; others cool the building structure . Because radiant surfaces are often cooled only a few degrees below the desired indoor air temperature, there are many opportunities for innovative cooling energy sources, such as night cooling and ground-coupled hydroponic loops. The heating and cooling supply water temperatures for radiant systems operate at higher set points compared to traditional systems. The radiant cooling system supply water temperature would typically operate at 15°C–18°C for cooling, whereas typical supply water temperatures for a traditional forced air system are around 5.5°C–7.5°C. The central cooling equipment can operate more efficiently at these temperature set points.In a typical office space, the airflow required to cool and ventilate the space can be three to four times greater than that required to just ventilate the space. If the space cooling is decoupled from the ventilation, especially through a hydroponic system, the central air handling system and associated distribution system can be downsized accordingly.