Abstract: Architecture in some of the densest cities in India (and the world) demands highly conscious spatial consumption with office design standards reaching efficiencies as low as 50sq.ft./person. Consequently, high internal gains and stress on available resources have led to innovative developments in the way these buildings need to be designed and built. Sustainable architecture must not only have a reduced impact on the environment but also needs to be flexible enough to cater to the changing usage of the building over an extended time period. Affordability or cost effectiveness, a key development factor in emerging nations often overrules the intention of sustainability, making it essential for these design strategies to be economically viable too. The critical balance between efficiencies for structure, area, occupants and resources needs to be established right from the conception level. Exploring the potential of adaptive comfort can help realize the possibility of using protected open spaces for user- interactive functions of a programme. The paper outlines the dynamics of an integrated design approach to practicing sustainable architecture in India, through an office building in Hyderabad. Located in the most prolific climate typologies in India, the design results demonstrate a balance of sustainability, spatial efficiency, economy and occupant satisfaction taking shape into 4 climate-responsive buildings. Keywords: Energy, Sustainability, Office-Design, Density, Commercial

Background Practicing environmental architecture in a developing country like India has unique advantages as well as challenges. Vernacular architecture is deeply rooted in passive design while urbanization has led to highly populous cities with 60% of the urban population living in metropolitan cities like New Delhi, Mumbai, etc. This has resulted in overcrowding, lack of space and consequently sky-rocketing real-estate rates equivalent to any other metropolitan city in developed nations. Design efficiency for the built environment is hence crucial and must bring together a comprehensive understanding of the principles of structural flexibility, optimised indoor environment controls, occupant comfort creating a holistic sense of identity for the overall macroclimate. The metrics of Sustainability, Affordability, Identity and Figure 1.Key parameters for commercial architecture

Climate Analysing the climate is the first step towards understanding the possible passive strategies applicable to the site. This process is critical in setting the project parameters for comfort and usability of open spaces. The prevalent tropical climate in India demands a combination of passive strategies for year-round comfort. Considering conventional occupancy for commercial buildings (9am-6pm), the external conditions indicate the potential to employ evaporative cooling strategies for the hot-dry period of the year. Physiological cooling is the most effective strategy for extremely humid situations demanding approaches that utilize the prevalent East-West winds at over 2.5m/s. High intensity of solar radiation adds to the challenge of creating a glare-free, 100% day-lit working environment while ensuring effective solar control (for reducing cooling loads). The Indian Model for Adaptive Comfortstudy (Green Rating for Integrated Habitat Assessment (GRIHA)-Appendix-1, The Energy and Resources Institute, 2015) addresses the thermal adaptability of people living in tropical climate typologies inherent to the country

Active Systems Thermal comfort has proven to be crucial in achieving occupant satisfaction as well as workplace productivity. Setting comfort targets when the end user is not involved makes it essential to consider not only the adaptive factor but also expectations of comfort which may vary for different climate typologies. Working spaces demand consistent and controlled indoor environments for minimal distraction during focused tasks. Although minimal, the cooling loads as a result of microclimate creation and robust envelope design needed to be countered with active systems to achieve the desired comfort levels indoors. Multiple cooling systems were analysed to achieve the most optimised solution specific to the project constraints. Innovative mechanical cooling systems including radiant cooling, under-floor systems as well as ceiling fans were explored in exclusive as well as combination scenarios. Feasibility analysisstudies concluded with the selection of under-floor cooling system for controlled thermal comfort requirements in working spaces. The primary advantage was that the system offers flexibility in internal layouts enabling any future changes in market standards and user requirements. An iterative process was followed where finally the mechanical system allowed higher operative temperatures at elevated air speeds of 0.5-1m/s using ceiling fans was finally concluded (Figure-6). Under-floor cooling systems are generally useful due to the stratification of air in high-volume spaces. Adding airmovement at ceiling level is undesirable in such cases as it is expected to counter the process. However, floor heights limited to 3.9-4.5M are unable to benefit from stratification since temperature variations only upto the range of 0.5-1°C are achieved. Enhanced air-movement in such spaces hence, significantly adds to the physiological comfort. The overall advantages offer flexibility to the architecture as well as active systems

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