Passive design indices: quantification of climatic potential for passive cooling strategies

The study aims to develop indices to assess the climatic potential of passive cooling strategies. Cooling accounts for 40% to 60% of summer energy demand in metropolitan cities with hot climates & air-conditioner (AC) sales in India are growing at 30% per year (CEM 2014). Recommendations based on current climatic zones may not be appropriate as many micro-climatic conditions and variations are found within a few kilometres. The current climate analysis tools do not explore the inter-relationships between climatic parameters. Earlier work showed that it is possible to develop a weather-data-based classification to map the potential of some basic passive design strategies, such as building orientation, layout, plan etc. This study takes that approach forward to establish weather-data-based indices for strategies such as evaporative-cooling, comfort ventilation, radiant cooling, earth cooling, and night ventilation. Weather data variables are identified for each strategy. Adaptive thermal comfort models represent the expected indoor comfort conditions. Typical Meteorogical Year (TMY) weather data of59 Indian cities are analysed to develop the indices. Thermal Autonomy and Discomfort Degree Days are the metrics developed to measure the potential of the passive strategies. An Excel processor and a Power BI user interface tool have been developed. These enable the user to compare the potential for strategies within a climate and compare various locations for their climatic potential for a strategy. The quantification of climatic potential for passive cooling strategies can become a key metric in assessing resiliency for climate change.