The insulation materials are used to improve thermal performance of buildings and their performance should be kept in required value during building life time, however long term change of thermal conductivity is observed for most of insulation materials. It is well known that the thermal conductivity of insulation foams increases with time due to the emission of the blowing agents from the insulation foams and the transfer of the air into them.
In this paper, the aging of thermal conductivity in various insulation foams is discussed with measured data and numerical analysis. Two kinds of accelerated test are conducted and the aging characteristics of various foams are examined. The estimation equations of thermal conductivity change of insulation foams are shown and applied to the measured materials. The effective diffusion coefficient of the blowing agents is obtained by comparing the simulation results and the measured value.