Older people generally want to live in their own homes for as long as possible. This can be facilitated by home modifications, but improving the thermal quality of their living environment remains under-researched. This paper discusses the application of building performance simulation to explore strategies to improve the homes’ thermal environment and their effects on older people’s thermal comfort, with the aim of developing design guidelines. Indoor temperature data recorded hourly were used to calibrate simulation models of four sample houses. Six strategies that affect thermal comfort were tested based on the thermal preferences of six older adults’ personas. Results show significant differences in the effectiveness of the strategies depending on the thermal preferences of the occupants, the house types, the seasons, and the climate zones. The study highlights the importance of considering occupant diversity and contextual factors when using building simulation to explore design strategies.