A methodology to evaluate the optimal insulation thickness for heating and cooling needs in different climatic zones for buildings made of reinforced concrete with cavity walls

: The study aims to define a methodology to evaluate the optimal insulation thickness with reference to the annual energy balance, including both heating and cooling seasons, for different climatic zones, based on three real case studies. The reduction of the heating needs due to the insulation of walls in places with cold climates is a consolidated concept. However, the effects of a high level of insulation of the envelope on the cooling needs has not yet been deeply analysed. The heating and cooling needs have been computed according to UNI/TS 11300 Italian standard by means of a commercial numerical model, varying the sizes of the buildings, the climatic zone, and the level of insulation. All the simulations concern buildings made of reinforced concrete frames with cavity walls, because of their wide diffusion as typical building technology of post war constructions. The work highlights the negative impact of the coating on the cooling needs, especially in the climatic zones with lower degree days. In almost all the climatic zones, the cooling need decreases its peaks during the hottest months (e.g., July or August), while the monthly load increases in the mild months (e.g., May, September) due to the additional thermal load which is no longer dispersed by means of the envelope. In conclusion, a range of optimal thicknesses for insulation for the different Italian climatic zones has been identified based on the total energy need of the building (cooling and heating).