Long-term performance of super insulating materials in building components & systems - IEA-EBC Annex 65

For households, heating and mobility are the two main loads of their energy burden. A large amount of the energy used for heating air and water is wasted through heat leaks of building envelopes and tank walls. For new building, it's possible to reach very low energy consumption thanks to a good design of building, a good airtightness, some solar gains in winter and efficient solar protections in summer but mainly and above all a good thermal insulation. In new building, the thickness of the insulating layer is ranking between 15 to 30 cm, with traditional insulating materials. This thickness in not acceptable for retrofitting and there is a growing interest in the so-called "super-insulating materials" (SIM), especially for internal thermal insulation. Except for a few types of cellular foams, all traditional insulating materials rely on still air embedded in cavities, pores or cells which prevent any convection. This is why the thermal conductivity of such materials reaches a minimum value, of about, 29 mW.m -1 .K -1 . To go beyond this limit and achieve superinsulation, three main principles can be applied to reduce thermal conductivity: - 1: Removing the gas : this technique is used for Vacuum Insulation Panels (VIP) - 2: Entrapping the ga s in tiny pores with a size lower than the mean free path of the entrapped gas in order to limit energy transfer between molecules: this technique is used for aerogel or other Advanced Porous Materials (APM). - 3: Changing the gas : this technique is similar to the one use for double glazing filled with argon or kr ypton Using one of these three options, the thermal conductivity of SIM is generally below 15 m.W.m -1 .K -1 and can reach very low values (close to 5 mW.m -1 .K -1 ). Only VIP and APM are now available on the market and integrated in building products but there is still a lack of information about long-term performances and installation techniques in order to foster the use of SIM in the building sector. The challenges of the IEA-EBC Annex 65 entitled "LongTerm Performance of SIM in Building Components & Systems" is to provide answer to these questions.