Impact of grey energy on optimal wall insulation thickness

For decades efforts have been made to reduce the greenhouse gases emissions of buildings by reducing their energy demand with governmental regulations in Europe, pushing towards very low thermal transmittances (U-values) with ever thicker insulation layers for new buildings. However, there is no linear relationship between the insulation thickness and the heat losses. Therefore, above a certain thickness the consumption of buildings does not decrease significantly. Hereafter a life cycle analysis, including emissions before the building becomes operational is applied to evaluate the impact of the increasing thickness of components on the overall emissions. Publicly available product data sheets are used to compare four insulation materials under three scenarios. These analyses yield interesting results showing that energy-intensive insulation materials lead to a negative impact in the overall energy balance after a certain thickness. Even though there is not always a pronounced optimum insulation thickness, it is logical that further reductions in U-value for new buildings should hence be carefully evaluated. The results show that the optimal thickness is around 20 cm for most materials, while the important major savings come from the first 10 cm.