Change over Time in the Thermal Conductivity of Ten-Year-Old PUR Rigid Foam Boards with Diffusion-Open Facings

Abstract

To estimate the long-term change in thermal conductivity of PUR rigid foam, various accelerated ageing processes (e.g. 70 °C ageing procedure) are used. Results of ageing processes are safety increments to cover a lifetime in practice of between 25 and 50 years. To compare estimated increments with the change over time in thermal conductivity of real boards, a research project was started. The research project was sponsored by the German Polyurethane Producers’ Association (IVPU) and funds of the German Minister of Economics over the AIF (Association of Industrial Research Institutes). The tables and diagrams show the thermal conductivity of PUR boards in full thickness and the cell gas composition over a period of ten years. The shape of the curves and the measured values are compared with the typical diffusion coefficients and thermal conductivity of cell gases. The development of the curves shows that the fixed increments in the European PUR standard EN 13165, 2001–10 for pentane blown PUR foams are correctly calculated. These fixed increments provide assurance for the users of PUR rigid foam boards over very long periods (e.g. 25 years) and give confidence to the builders and the building supervisory authorities.