The performance evaluation method for wooden fire preventive construction with combustible insulation in the Ministerial approval procedure has been significantly rationalized, as the rating for fire preventive performance have been clarified according to the insulation material property at high temperature. The following technical knowledge made this rationalization possible. Under the condition that the insulation material is protected by interior and exterior fire resistive materials, combustible insulation does not burn intensely, but melts and thermally decomposes from the heated side. Therefore, the fire preventive performance of the exterior wall does not decrease even if combustible insulation is used.
