**Kanittha Pamonpol 1,\*, Thanita Areerob <sup>2</sup> and Kritana Prueksakorn 2,3,\***


Received: 21 January 2020; Accepted: 3 March 2020; Published: 9 March 2020

**Abstract:** Optimum thermal comfort and good indoor air quality (IAQ) is important for occupants. In tropical region offices, an air conditioner is indispensable due to extreme high temperatures. However, the poor ventilation causes health issues. Therefore, the purpose of this study was to propose an improving IAQ method with low energy consumption. Temperature, relative humidity, and CO2 and CO concentration were monitored in a poorly ventilated office for one year to observe seasonal variation. The results showed that the maximum CO2 concentration was above the recommended level for comfort. Simple ventilated practices and placing a number of *Sansevieria trifasciata* (*S. trifasciata*) plants were applied to improve the IAQ with the focus on decreasing CO2 concentration as well as achieving energy saving. Reductions of 19.9%, 22.5%, and 58.2% of the CO2 concentration were achieved by ventilation through the door during lunchtime, morning, and full working period, respectively. Placing *S. trifasciata* in the office could reduce the CO2 concentration by 10.47%–19.29%. A computer simulation was created to observe the efficiency of simple practices to find the optimum conditions. An electricity cost saving of 24.3% was projected for the most feasible option with a consequent reduction in global warming potential, which also resulted in improved IAQ.

**Keywords:** computational fluid dynamics; CO2 concentration; indoor air quality; *Sansevieria trifasciata*; ventilation
