Glass fiber-reinforced polymer (GFRP) composites have been used in civil construction because of their high strength, lightweight, and corrosion resistance. However, their thermal sensitivity due to the polymer resin requires further understanding of the fire performance of these structures, because the heat from the fire could cause glass transition and decomposition of GFRP composites and degrade their mechanical properties. Fire dynamic simulations were conducted in this study to investigate heat propagation, which considered airflow aerodynamics, in typical single-story residential houses with walls and roofs in the form of GFRP web-flange sandwich structures. The temperature progressions and gradients in the GFRP wall and roof members were quantified, which allowed for the identification and further understanding of the locations and development of glass transition and decomposition in the GFRP composites during fire exposure. The effects of the building floor layouts, fire source locations, additional fire resistance gypsum plasterboard, and a fresh air supply were further discussed and clarified.