Selection criteria of thermal mass materials for low-energy building construction applied to conventional and alternative materials

• Proper analysis of materials use for buildings envelops can lead to the reduction in energy consumption and GHG emission.
• CES selector software is a relevant tool to assess and compare potential materials using specific criteria.
• In terms of thermo physical properties and cost, recycled ceramic materials are more performant than conventional ones.
• The too important embodied energy of recycled ceramics can be balanced by hybridation of vitrification processes.

According to the recent worldwide environmental problems, there is a need to reduce the energy consumption and the green house gas emission of the building sector. Therefore, the properties and performances of the building envelops have to be enhanced before considering any energetic equipments. A particular attention should then be made in the selection of the materials used in buildings. The scope of the present paper is to propose tools for selection and comparison of construction materials and especially thermal mass materials. The CES selector software has been used to compare conventional materials to new recycled ceramics in terms of thermal properties, mechanical properties, cost and embodied energy. The recycled ceramic, made of inert vitrified asbestos containing wastes, is a good alternative material presenting one of the best thermal and mechanical properties for a very low price. Its use as thermal mass material offers a new life cycle with a pay-back of its embodied energy needed for the waste treatment. Nevertheless, the high temperature waste treatment process leads to a too high embodied energy before conventional materials. This aspect highlights the need in new hybrid vitrification processes taking advantage of renewable energies such as concentrated solar technologies. Finally, the dynamic thermal behavior of a wooden house prototype was simulated using the thermal mass materials previously studied. The influence of the selected materials on the inside comfort of the house was analyzed using the French software «Pléiades + Comfie» under dynamic outside temperature variation. The combination of thermal inertia, incoming solar flux control and nocturnal over ventilation leads to a whole indoors temperatures range closed to the comfort standard level.