In the pursuit of stricter energy standards for buildings to reduce their share of energy use, the use of highly efficient insulation materials like aerogel and vacuum insulation has opened a path towards lighter construction in energy retrofitting, whereas commercially available materials, such as EPS and mineral wool, result in massive wall solutions. However, these new materials are notoriously energy intensive in production, resulting in high levels of embodied energy and emissions.
This work describes a comprehensive greenhouse gas analysis of the use of different insulation materials applied to residential building upgrades to passive house standard. It estimates the potential environmental disadvantages of using such materials in energy retrofitting.
A social housing complex from the late 1960s, located in Oslo, is used as test case. The building is upgraded to passive house standard. The facades are renovated by reducing the wall thermal conductivity to a U-value of 0.10 Wm-2K-1. This is achieved by applying correspondingly appropriate thicknesses of mineral wool, aerogel and vacuum insulation. A cradle-to-grave analysis is then performed on the facade components to determine the global warming potential of each proposed insulation option. Special attention is given to the share of the embodied emission over the building lifetime, by varying the electricity-CO2 conversion factor as well as the lifetime of the renovated building. Comparisons between the resulting energy demand and embodied emissions are presented.
Results show that the shares of embodied emissions of the options with mineral wool, aerogel and vacuum insulation are 13%, 29% and 49% of the total building lifecycle emissions, respectively. Despite the fact that aerogel and vacuum insulation have a global warming potential which is between four and eight times higher than that of mineral wool, the resulting effect is a minimal difference between the retrofitting alternatives. This is due to the limited amount of mass of vacuum insulation and aerogel needed to obtain a U-value equivalent to that of the wall equipped with mineral wool.