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A large amount of energy is used to heat and cool buildings in the construction industry. Moreover, wood frame buildings’ relatively low thermal mass limits energy efficiency and thermal comfort. Thermal energy storage via latent heat can effectively increase the thermal inertia of the building envelope, minimising the indoor temperature fluctuations and improving the occupant thermal comfort. This paper evaluated the energy efficiency and thermal comfort of an air-conditioned wood frame building by using biobased phase change materials (PCM) as the middle layer of a building envelope. Numerical simulations were conducted to investigate the effect of different factors (PCM melting point, surface area, thickness, and position) by adding a PCM layer into building walls to reduce annual heating and cooling energy consumption. The results of the numerical simulations showed that a phase change material layer can effectively decrease the energy demand of buildings, especially in cold areas. Based on the conditions investigated, the optimum solution can reduce the cooling, heating and annual energy consumption by 47%, 34% and 38%, respectively, compared to a reference building without a PCM layer. Moreover, an economic and environmental study of buildings containing biobased PCM is presented.