Indoor thermal comfort analysis of TABS with untreated natural ventilation in a warm and humid climate – An experimental study

•Investigated the thermal comfort of the occupants’ using TABS.•Impact of untreated natural ventilation on thermal comfort for TABSs is evaluated.•Sensitivity analysis was performed.•Optimized flow regime for energy saving and thermal comfort of TABS was identified. Thermally activated building systems (TABS) are the most environment-friendly and energy-efficient cooling technology. These cooling methods, which use pipe-encapsulated building surfaces to minimize the indoor cooling load, have been used in this work. The primary objective of the research is to measure the energy use, thermal comfort and the impact of cooling surface area and water inlet flow velocities on the performance of TABS with natural ventilation assistance in a warm and humid environment. Experimental studies were conducted to investigate the impact of cooling surface area and water inlet flow velocities on the performance of thermally active buildings with natural ventilation assistance. Natural ventilation had a significant impact on advancing and increasing the average indoor air temperature by 1.5 °C when compared to the neutral adaptive comfort band. The increase in the water inlet velocity from 0.35 to 1.5 m/s substantially removes the thermal energy stored in the TABS system by reducing the average indoor temperature by 2 °C. The predicted percentage dissatisfied (PPD) was approximately 40% of all cooled surfaces. The energy consumption for 1 m/s water inlet velocity, which provides similar thermal comfort for higher flow rates, is 1.3 kWh. Therefore, from the study, 1 m/s water inlet velocity is found to be the optimal value, where comfort and energy consumption are within an acceptable range. Hence, the operating parameters under which the building envelope is cooled would significantly impact the performance of the thermally activated building system.