The public and scientific debate about the added value of investments in renovation of buildings has been ignited by the recent heat wave in Europe. Some renovations that were primarily concerned to safe energy in winter through better isolation of walls, doors and windows found themselves less well prepared with isolation against heat and sunlight. Hence, it makes sense to consider both topics, cooling and heating of buildings, jointly.
Reversible heat pumps can do this trick, if isolation has been installed or applied during renovation already. Additionally, materials used for isolation of buildings should show 2 measures for isolation: thermal conductivity and thermal resistance (R-value). Comparing both gives a fair idea about isolation quality in periods of heating and cooling needs. Albedo values are interesting as well as heat input during a sunny day is welcome in winter, but not during summer heat waves. The commonly used Energy Performance Certificate (EPC) for a building needs to be checked whether it is sensitive to excessive heat as well. (Image: BNF in Paris 2026)
