Exploring impact of opaque building envelope components on thermal and energy performance of houses in lower western Himalayans for optimal selection

• Empirical data about thermal performance of houses in tropics through field-study.
• Building energy simulation is done to find potential annual energy savings.
• Thermal mass, wall and roof insulation are good for thermal comfort in composite climate.
• HVAC load in buildings can be reduced significantly by using wall and roof insulation.

The building envelope plays crucial role of both protecting its occupants from external environment and controlling indoor environment to maintain indoor thermal comfort condition and energy-efficiency. The main aim of present day building design should be eliminating the need for mechanical heating and cooling equipment wherever possible. A novel approach is applied in this study to find empirical data through field experimentation conducted in the study area to derive the proposal suitable for the buildings of that location. Field studies of naturally ventilated residential buildings were conducted at Mandi town, located in western Himalayan Indian state of Himachal Pradesh with composite climate, during winter and summer months of 2013 and 2014 to assess the impact of opaque building envelope materials on indoor thermal condition. Further, energy performance of residential buildings is analyzed using e-QUEST building-energy simulation tool to find the potential annual energy consumption and energy savings during the functioning of buildings. The study found that the use of thermal mass in wall and roof construction can maintain indoor thermal comfort during winter and summer months in composite climate. The study also found that the application of wall and roof insulation can maintain indoor thermal comfort condition in modern houses during winters and summers and can also improve energy-efficiency of partially and fully air-conditioned buildings significantly – the heating, cooling and mechanical ventilation load can be reduced up to 60%, 40% and 40% respectively; the peak energy demand during summer and winter can also be reduced. Further research area is also identified.