K. Dharmasastha

Bio: K. Dharmasastha is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Thermal comfort & Roof. The author has an hindex of 2, co-authored 3 publications receiving 43 citations.

Thermal comfort in traditional buildings composed of local and modern construction materials

Abstract: In recent years, there is a renewed interest towards the passive cooling features of ancient building architectures, which are cost effective, eco-friendly and best suited for the local climate. On the other hand, the modern construction materials, such as cement and steel, are highly durable. Thermal comfort of eight vernacular buildings that use modern construction materials to improve the structural durability was monitored in July 2014. The buildings are located in Hyderabad, India. They have many passive cooling features that include air cavities in the structures to reduce heat transfer, high thermal mass to reduce temperature fluctuation and induced ventilation to remove heat from the indoor. All the passive cooling features investigated were found to have an appreciable influence on the thermal comfort of the indoor space. The ventilated air gaps in the roof reduced the average temperature of the roof interior surface by 1.2 °C. The diurnal temperature fluctuation of the indoor air reduced by 0.9 °C in a building with a higher thermal mass compared to a building with thin walls and roof. All the eight buildings were found to be comfortable most of the time with a slight discomfort during late night and morning hours. The maximum CO 2 recorded was 550 ppm. This indicates that the buildings were adequately ventilated.

Impact of Indoor Heat Load and Natural Ventilation on Thermal Comfort of Radiant Cooling System: An Experimental Study

Abstract: Construction and operation of buildings are responsible for about 20% of the global energy consumption. The embodied energy of conventional buildings is high due to the utilization of energy-intensive construction materials and traditional construction methodology. Higher operational energy is attributed to the usage of power-consuming conventional air-conditioning systems. Therefore, moving to an energy-efficient cooling technology and eco-friendly building material can lead to significant energy savings and CO2 emission reduction. In the present study, an energy-efficient thermally activated building system (TABS) is integrated with glass fiber reinforced gypsum (GFRG), an eco-friendly building material. The proposed hybrid system is termed the thermally activated glass fiber reinforced gypsum (TAGFRG) system. This system is not only energy-efficient and eco-friendly but also provides better thermal comfort. An experimental room with a TAGFRG roof is constructed on the premises of the Indian Institute of Technology Madras (IITM), Chennai, located in a tropical wet and dry climate zone. The influence of indoor sensible heat load and the impact of natural ventilation on the thermal comfort of the TAGFRG system are investigated. An increase in internal heat load from 400 to 700 W deteriorates the thermal comfort of the indoor space. This is evident from the increases in operative temperatures from 29.8 to 31.5 °C and the predicted percentage of dissatisfaction from 44.5% to 80.9%. Natural ventilation increases the diurnal fluctuation of indoor air temperature by 1.6 and 1.9 °C for with and without cooling cases, respectively. It reduces the maximum indoor CO2 concentration from 912 to 393 ppm.

Performance study of thermally activated glass fibre reinforced gypsum roof.

Abstract: Globally, building sector consumes a large amount of energy both for construction and operation. Especially, heating, ventilation and air conditioning contribute for 40 – 50% of total building energy consumption. Thermally Activated Building System (TABS), which is an energy efficient alternative to conventional mechanical air conditioning, can reduce the energy consumption of building operation. TABS is a radiant cooling technology, which utilizes the thermal mass of the building to achieve thermal comfort of the indoor space. In TABS, chilled water circulates through the pipes, which are embedded in the building structure. Chilled water removes the heat from the indoor and provides a comfortable indoor to the occupants. In addition to TABS, use of appropriate building material can enhance the energy-saving potential of buildings not only by reducing the cooling/heating load but also by reducing the embodied energy of the building. A sustainable and eco-friendly building material, namely Glass Fibre Reinforced Gypsum (GFRG) can be integrated with the TABS. The combination of TABS and GFRG is named as Thermally Activated Glass Fibre Reinforced Gypsum (TAGFRG). The present study aims to analyze the impact of various design and operating parameters on the performance of TAGFRG roof. A TAGFRG roof has been designed by embedding water flowing copper pipes along with the provision of air gaps in the structure. A commercial CFD tool has been used to simulate the TAGFRG roof. The design and operating parameters analyzed are diameter, wall thickness and thermal conductivity of pipe, pipe spacing, and temperature and flow rate of supply water.

Studies on sustainable features of vernacular architecture in different regions across the world: A comprehensive synthesis and evaluation

Abstract: Due to the increasing pressure brought by recent global environmental problems, building designers are embracing regionalism and the knowledge of traditional structures, arguing that these structures are energy efficient and highly sustainable. We observe clear evidence of the increasing interest in vernacular architecture among the research community. This study therefore aims to clarify the contents and issues raised in the studies on vernacular architecture and the knowledge and recommendations that can be derived from them. A database of the research is established by collecting many studies from primary sources. Obtained data is carefully refined and categorized into a table where synthesized information is introduced. The results of this study show an uneven geographic and climatic distribution of the studies; the trend in selecting research objectives and research objects; the choice of research methods with a clear shift towards quantitative research methods, and the generic findings from the database of the research. These results can support diverse inquiries about vernacular architecture across the world and be used as a resource or an orientation to support numerous subsequent studies.