Durability of insulating materials: a comparison between traditional and nanocomposite mortar thermal insulating, basing on the thermal conductance measured by means of the heat flow meter approach

Every insulating material has to meet the double requirement of thermal performance and durability. While the conductivity grants a proper thermal resistance, durability represents a crucial planning aspect to assess the long-term building performance from the point of view of costs and environmental impact. Differently from traditional insulators, the recent nanotechnological mortars claim to provide dramatic insulating performances and there is no consolidated evidence about both reliable thermal performance (e.g. CE marking, ETA, third party laboratory tests) and durability. The present paper compares the durability and thermal performance of two different scenarios by means of the heat flow meter approach: a stone wall covered with nanotechnological insulating mortar and a brick wall insulated with polystyrene. The thermal conductance of the former case shows a difference between measured and self-declared values of about +500% after the end of the installation cycle. Two years later, the conductance almost doubles, showing very poor thermal performance and durability, against the not representative, self-declared values. In the latter case, the wall thermal conductance after about 30 years is still aligned with the original design performed in 1995, showing very good durability of the performance declared in the original, standard compliant design dating back to the time.