Windows plays an important role in heat transfer in buildings. One of the energy reduction alternatives that can be incorporated into modern building design is the installation of efficient windows. The windows should allow thermally acceptable thermal comfort and have a pleasant design while being energy efficient. Good thermal conditions in educational buildings, especially learning spaces, promote the educational process. One variable that affects the thermal comfort condition is indoor air temperature. In this paper, using Computational Fluid Dynamics (CFD) simulation techniques, the effects of window glass types on the indoor air temperature of thermal comfort in a discussion room at Universiti Teknologi MARA (UiTM) Cawangan Pulau Pinang, Permatang Pauh campus are studied. The simulation result will be compared to standard regulations by the American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) Standard 55–2017. Three different types of window glass were selected in this study: float glass, reflective glass, and low E-coated glass windows. It was found that the indoor air temperatures for certain points of float and reflective glass windows are above the range limit by ASHRAE Standard 55–2017 but the air temperature for low-E coated glass windows is in the range limit. Compared to float and reflective glass, low E-coated glass can effectively reduce heat transfer through the windows. Therefore, low E-coated glass windows provide better thermal comfort in indoor air temperatures.