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While the operational energy use of buildings is often regulated in current energy saving policies, their embodied greenhouse gas emissions still have a considerable mitigation potential. The study aims at developing a multi-objective optimization method for design and renovation of buildings incorporating the operational and embodied energy demands, global warming potential, and costs as objective functions. The optimization method was tested on the renovation of an apartment building in Denmark, mainly focusing envelope improvements as roof and exterior wall insulation and windows. Cellulose insulation has been the predominant result, together with fiber cement or aluminum-based cladding and 2-layered glazing. The annual energy demand has been reduced from 166.4 to a range between 76.5 and 83.7 kWh/(m2 y) in the optimal solutions. The fact that the legal requirements of 70 kWh/(m2 y) are nearly met without building service improvements indicates that energy requirements can be fulfilled without compromising greenhouse gas emissions and cost. Since the method relies on standard national performance reporting tools, the authors believe that this study is a preliminary step towards more cost-efficient and low-carbon building renovations by utilizing multi-optimization techniques.

The energy-saving potential in buildings (e.g. buildings proposed for an energy upgrade in an energy policy context) is often overestimated because implicit factors, such as rebound effects, are ignored. In order to get an accurate estimate of the realisable energy-saving potential in a building stock, these factors, as well as how they differ among buildings with different characteristics, must be accounted for.On the building stock level, detailed information about the actual conditions in each building (e.g. indoor temperatures, domestic hot water consumption, internal heat loads, etc.) is rarely available. In its place, fixed assumptions are often made, usually disregarding the characteristics of the buildings. Therefore, a method that is based on available building stock data is needed for adjusting this technical energy-saving potential.This study investigated how the heat consumption in residential buildings might be expected to change due to an energy upgrade, using a hybrid bottom-up model of the Danish residential building stock. Pseudo-rebound effects, inherent to the thermal standard of the building, were quantified in a sample of 134.000 buildings with different characteristics.Results showed that estimating the heat-saving potential on the basis of the thermal characteristics alone (i.e. the technical heat-saving potential), would lead to a considerable overestimation of the realisable heat-saving potential in the residential building stock. However, the size of the realisable heat-saving potential was found to vary considerably among buildings with different characteristics, despite having the same technical potential. This indicated that the technical heat-saving potential should be corrected differently in buildings with different characteristics.