The influence of different electricity-to-emissions conversion factors on the choice of insulation materials
Authors: Publication Year: 2014


The current practice of building energy upgrade typically uses thick layers of insulation in order to comply with the energy codes. Similarly, the Norwegian national energy codes for residential buildings are moving towards very low U-values for the building envelope. New and more advanced materials, such as vacuum insulation panels (VIPs) and aerogel, have been presented as alternative solutions to commonly used insulation materials. Both aerogel and VIPs offer very high thermal resistance, which is a favourable characteristic in energy upgrading as the same insulation level can be achieved with thinner insulation layers.

This paper presents the results of energy use and lifecycle emissions calculations for three different insulation materials (mineral wool, aerogel, and vacuum insulation panels) used to achieve three different insulation levels (0.18 W/m2 K, 0.15 W/m2 K, and 0.10 W/m2 K) in the energy retrofitting of an apartment building with heat pump in Oslo, Norway. As advanced insulation materials (such as VIP and aerogel) have reported higher embodied emissions per unit of mass than those of mineral wool, a comparison of performances had to be based on equivalent wall U-values rather than same insulation thicknesses. Three different electricity-to-emissions conversion factors (European average value, a model developed at the Research Centre on Zero Emission Buildings – ZEB, and the Norwegian inland production of electricity) are used to evaluate the influence of the lifecycle embodied emissions of each insulation alternative. If the goal is greenhouse gas abatement, the appraisal of buildings based solely on their energy use does not provide a comprehensive picture of the performance of different retrofitting solutions.

Results show that the use of the conversion factor for Norwegian inland production of electricity has a strong influence on the choice of which of the three insulation alternatives gives the lowest lifecycle emissions.

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