Ventilation control approach for acceptable indoor air quality and enhancing energy saving in Thailand

Nowadays many people spend most of their time indoors, so the quality of indoor air has significantly impacted human health and comfort. The purpose of the present work was to determine the thermal comfort and suitable air intake rate for Thai people in air-conditioned buildings. A field study was conducted in three types of building from six provinces of Thailand; 698 occupants responded to the questionnaire while simultaneous indoor air quality measurements were taken. The results showed the suitable air intake rate is 9 L/s (19 cfm) per person for office buildings, 12 L/s (25 cfm) per room for hotel buildings and 7.5 L/s (16 cfm) per person for institutional buildings. The thermal acceptability of Thai people varied between 23±0.5 °C and 26±0.5 °C. The mean neutral indoor temperature is 24 °C. The result derived from this study is a prescribed cyclical on-off ventilation control approach for maintaining an acceptable indoor air quality with efficient energy usage for air-conditioned buildings. The numerical simulation and real-time investigation in a small size office, 4.80x3.90x2.55 m³, with 1-2 occupants, was used for analysing the efficiency of this approach. The study revealed that the optimised ventilation cycle time is composed of 2 cycles as follows: 1) 90 minutes cycle time with 70 minutes switched 'on' and 20 minutes switched 'off'; 2) 60 minutes cycle time, with 50 minutes switched 'on' and 10 minutes switched 'off'. The results showed that this approach can maintain the indoor carbon dioxide (CO₂) concentration below 1000 ppm in the experiment room and the energy consumption can be reduced by up to 9% of the original ventilation load. This ventilation control approach has proved to be feasible for use in new buildings and in the retrofit of existing buildings in relation to economical cost, combined with the absence of a need for a sophisticated controller or expensive equipment such as CO₂ sensors. This ventilation approach is particularly suitable for integration into Thai air-conditioned buildings as it can provide acceptable indoor air quality and reduce electrical energy consumption.