GREEN BUILDING CONGRESS 2011 NEW DELHI

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1 DEVELOPING GUIDELINES FOR ENERGY EFFICIENCY IN RESIDENTIAL BUILDINGS IN INDIA Background The Energy Conservation Building Code (ECBC) has addressed the need for energy efficiency to prepare for the growth of the commercial building sector. It is now seen that there is a phenomenal growth in group housing for the middle class in an around the urban centers across the country. It is also anticipated that the combination of -Changing lifestyles of middle class households, a growing desire of air conditioned comfort and a shift towards multistorey residential buildings is going to create a new frontier of escalating energy demand. GREEN BUILDING CONGRESS 2011 NEW DELHI GREENTECH, SORANE, TARA NIRMAN KENDRA AND ASHOK B.LALL ARCHITECTS THEREFORE, THERE IS A NEED TO DEVELOP GUIDELINES FOR ENERGY EFFICIENCY IN RESIDENTIAL BUILDINGS IN INDIA Research Team GREENTECH KNOWLEDGE SOLUTIONS PVT. LTD., New Delhi SORANE SA, Switzerland TARA NIRMAN KENDRA, New Delhi ASHOK B. LALL ARCHITECTS, New Delhi This work has been supported by Embassy of Switzerland, New Delhi. Objective The Guidelines will address : Reduction in Operational Energy Reduction in Embodied Energy while maintaining occupant's thermal comfort and safety Proposed Guideline will give recommendations on following aspects of Residential building designs : Spatial Configuration and Building Densities Research Status This is work in progress. A methodology for work under the above mentioned aspects is proposed. Preliminary sample surveys and simulation are conducted. General inferences are drawn from the work done so far. Spatial Configuration and Building Densities Rationale Due to the need to curtail suburban spread for a more sustainable compact city form, there is an inevitable rise in the density of urban residential development. It is now common for city planning authorities to encourage Floor Space Index (FSI) of up to 4 ; FSI of 1.5 to 2 is becoming commonplace. Surface Layer Heat Islands and Canopy Layer Heat Islands would have a bearing on indoor temperature, thermal comfort and consequently on cooling loads. Research has shown that, The heat island effect has a direct correlation with radiation absorption characteristics of the ground & roof surfaces and the absence of vegetative cover. The contribution of anthropogenic heat Vehicular fuel combustion, home appliances, electromechanical equipments in buildings and air conditioners is also understood. The influence of spatial configuration of built & open space and the thermal mass of buildings on ambient conditions around buildings is not so well understood. Recharge of Ground Water Water percolation Ground water almost finished

2 Spatial Configuration and Building Densities Methodology The range of building height and the ground coverage that is commonly in practice today was adopted to generate a spread of Builtupness cases. Three idealized typologies of plan configuration are taken for study at varying degrees of builtupness : Pavilion Type: Tower structure with central core and residential units around it. Street Type: Row linear housing Courtyard Type: Residential units enclosing open space ENVIMET softwarewas used to predict ambient temperature conditions around buildings. A typical summer day was studied. Rationale Given that the window of opportunity for reversing climate change has a horizon of the next ten years and also that the boom of residential building construction is expected to be at its height in the same decade, the contribution of embodied energy to CO2 emissions draws our attention. Carbon dioxide emissions on account of the energy consumed in production of residential buildings (Embodied energy ), as against their consumption of the operational energy, will be significant in the context of rapid urban development / m h 600 k W Embodied Energy (kwh/m2) Years Operational Energy (kwh/m2) Inferences Based on the observations of this study some design recommendations maybe made: Design for low rise developments with adequate vegetation appears to be more advantageous model. Vegetation plays a significant role in reducing heat island effect. Building configurations favoring passage of natural breezes e.g. courtyard forms with open corners are desirable. For medium densities a combination of low rise with occasional high rise block is preferred. Pavilion Street Court This is on account on three factor the adoption of more energy intensive construction materials and techniques compared to traditional construction methods switch over to multistory frame construction using reinforced cement concrete relatively modest operational energy consumed in the residential sector. At a conservative estimate the impact of embodied energy at the start of a residential building s life is as much as operational energy spent over 10 years. Methodology A data base of currently valid embodied energy in production of materials in India taking into account improved industry practices was established. Embodied Energy analysis of typical multistory building shows that approximately 80 percent of the embodied energy of the total buildings is attributed to structural systems and external walls. The structural and external walling systems embodied energy is calculated for following types of buildings using the construction materials data of a representative building of each type : A. Building as usual -G+3 Hybrid Structure using burnt brick for walling. -G+8 RCC Frame with burnt brick infill. B. Environmentally conscious design -G+3 Hybrid Structure using load bearing Fly ash brick wall. -G+10 with Aerated Concrete Block Walling. Embodied Energy and Co2 Emissions per Unit area of net residential space of the above examples is compared. Embodied Energy Reinforcement steel MJ/Kg Cement MJ / Kg Reinforcement Steel 55% Brickwork 8% Fenestration 6% Plaster 2% Paint 2% Flooring 4% Concrete 23% ANALYSIS OF TYPICAL LOW RISE (G+3) TYPICAL STRUCTURE Steel, when viewed in relation to the quantity used, contributes the maximum to the embodied energy. Although it constitutes just 2% of the material by weight in the building structure, but it is responsible for 34% of embodied energy and 26% of CO2 emissions Cement s contribution to CO2 emissions is proportionally higher than steel, even though steel (at 27.3MJ/kg) has a much higher embodied energy than cement (3.2MJ/kg). This might be due to the difference in the carbon factor of various fossil fuels and their quantities used in the production process.

3 Rationale and Methodology Energy Consumption in Middle Class Home is a function of lifestyle, thermal comfort aspirations thermal characteristics of the building envelope and local climate. The present focus is on composite climate and warm humid climate zones. For low rise buildings, considerable reduction in embodied energy might be possible by careful designing and using materials with low embodied energy. The embodied energy of IIPH is 30% lower than that of DDA. The material for wall construction has a major impact on the total EE in load bearing construction. In high rise buildings, there an indication that EE/sq.m increases with height of building. This may suggest greater efforts required for steel efficient structural design. The range of CO2 emissions shows that in a well designed low rise building emissions are 30-40% less than an average high rise building incorporating a RCC frame structure. Giving preference to low rise buildings (G+4) in residential development and using low embodied energy materials for external walling of a potential % reduction in EE/Sq. M. of residential space compared to BAU. It is anticipated that energy consumption will rise principally on account of homes resorting to air conditioning to obtain comfort. In order to establish a reference baseline in relation to which energy conservation may be measured, an empirical preliminary database of energy consumption patterns is to be gathered and analyzed. The complement of energy consumption on account of thermal comfort as a proportion of the total energy consumption is inferred The potential of reducing cooling loads for comfort by integrating passive and active cooling systems is modeled by computer simulation. Sample Household Survey The data for Abhiyan Apartments in Delhi (78 households) for theyear , , shows a trend of increased average monthly electricity consumption per household. Sample Household Survey For Delhi-NCR, average EPI of residences was computed as 47 kwh/m2/year. For Chennai, average EPI of residences was computed as 38 kwh/m2/year. In a typical Chennai home airconditioning and ceiling fans electromechanical aids for comfort consumes approximately 55 % of the energy bill. There is an emerging trend of houses with EPI above 80 kwh/sq.m./year which are typically houses with 2 or more air conditioners and 4 or more occupants. This trend is visible in both climate types. Monthly EPI distribution for sample residential developments in Composite Climate (Delhi-NCR) and Warm & Humid Climate (Chennai) -The graph indicates high peak for energy requirements during summer period in composite climate. In warm and humid climate, space cooling is for extended duration but with low amplitude of peak. This is due to lower peak temperatures and utilization of cool evening sea breeze for natural ventilation. November could be considered as base month in composite climate, where energy is mainly used for operation of lighting and basic household appliances. There is practically no requirement of energy for space cooling or heating during November.

4 Simulation Study for Delhi 1 Good Natural Ventilation can provide adaptive comfort for a considerable time (30-35% of the time as per simulation results) of the year. While designing the building, suitable openings (20-30% Window-to-wall ratio and windows evenly distributed to allow cross ventilation) should be provided for natural ventilation Ventilation can also be achieved through mechanical systems i.e. assisted ventilation. If natural ventilation is not good in the building then assisted ventilation can provide the adaptive comfort. Efficient envelope can significantly reduce the heat ingress and improve the adaptive comfort in summers. With improved envelope natural ventilation is more effective ; comfort duration is doubled from 20% to 40% of the time in a year. Typical envelope measures include external wall insulation, roof insulation and double glazing with shading. It is very important to put the insulation on the outer side of the wall/roof so that the coolness is stored in the walls/roof which will help in maintaining the room temperature lower. 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Impact of Building Envelope with Natural Ventilation Daytime.BAU Nighttime.BAU Daytime.ECBC Nighttime.ECBC Apr May Jun Jul Aug Sep Simulation Study for Delhi 1 The simulation results compare the Business As Usual (BAU) case with the High Performance Energy Conservation Building Code (ECBC) case as per the specifications If we prioritize the cooling systems and consider adaptive comfort, load on air-conditioner can be significantly reduced. Simulation results show that with the use of natural ventilation and evaporative coolers (with adaptive comfort), the air-conditioner is required only for 1/3rd of the time during the cooling season (April-September). Evaporative coolers are very well suited for this climate as in the peak summer months (May-June), they can provide adaptive comfort for around 40% of the time. The ECBC efficient envelope reduces cooling load by approximately 40% compared to BAU. Simulation Study for Delhi 2 Another energy simulation* was carried out with TRNSYS energy and systems simulation software on an existing 7-storey building in New Delhi. The parametric study aimed at assessing the Energy Saving Potential of different design strategies includingpassive Design Strategies and Alternative Active Cooling Systems, as well as a combination of both passive and active strategies. This may be considered an idealized design. The Passive Design Strategies included: Solar Protection in the way of Exterior Blinds and Overhangs Natural Ventilation 10 cm Outside Insulation (Expanded Polystyrene) Double Glazing with low Solar Heat Gain Coefficient White finishes on Exterior Walls Alternative Active Cooling Systems included : Indirect adiabatic cooling and, for the remaining cooling load, a new generation high-performance air conditioner with an evaporative condenser. The optimal solution combines both passive design and active cooling solutions, achieving more than 85% savings in the cooling load. Simulation Studies indicate a potential of % saving in operational energy compared to BUA Summary of Work in Progress SPATIAL CONFIGURATION AND BUILDING DENSITIES Planning regulations and developing controls are indicated in order to minimize urban heat island effect. These will include maximization of soft ground and green cover, minimization of motorized vehicle and road surfaces Further work is necessary to understand the correlation between density / building configuration and urban heat island. Guidelines would contain tips on optimizing orientation / shading / passage of breeze for different densities and spatial configurations. EMBODIED ENERGY: BUILDING STRUCTURE & FINISHES A general recommendation for giving preference to low rise (G+3) is indicated. Innovative structural design to minimize steel content is strongly indicated. Low embodied energy walling materials substitute for burnt brick or concrete block are clearly recommended % savings on account of embodied energy is an indicated target. BUILDING ENVELOPE AND OPTIMIZED SPACE CONDITIONING Residential buildings need to incorporate all passive strategiesin anticipation of the desire for air conditioned comfort Design Guidelines need to explore technical integrations and feasibility of natural / assisted ventilation and adiabatic cooling 60% energy savings is an indicated target where air conditioned comfort is desired.

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