Impact of future scenarios on building renovation strategies

Abstract

The present situation is that buildings worldwide account for 40% of the global energy consumption. This in turn leads to a large amount of emissions which have an impact on the ecological diversity and our environment due to global warming. The target of the international energy agency (IEA) is to achieve a reduction of 80% for global emissions by 2050. In order to address this issue, this thesis aims to find an optimal renovation strategy in terms of lowest environmental impact through life cycle assessment (LCA) as well as assessing the robustness towards future scenarios in a sensitivity analysis. The focus is set on the illustration of the potential of new renovation technologies in comparison with common strategies presently utilised. In order to derive a reliable recommendation, the reference project of the research program “house of tomorrow – plus” localised in Kapfernberg, Austria is studied.

The starting point of this study is by assuming that the consideration of the building parameters, which are expected to have the greatest relevance to the overall environmental impact, are sufficient for the derivation of reliable LCA results. Based on this assumption, the study is approached by elaborating various renovation scenarios (e.g. inclusion of solar thermal area or change of energy supply to district heating) and by modelling as well as evaluating the environmental impact in a life cycle inventory assessment (LCIA). The indicators utilised for this assessment are cumulative energy demand (CED), global warming potential (GWP 100a) and ecological scarcity 2006 (UBP). In a next phase, the impact of future energy scenarios due to climate change combined with a diversification of electricity mixes is assessed for the various renovation scenarios in a sensitivity analysis. Its result indicates the robustness of each renovation scenario. On the basis of this methodological approach, the results of the scenarios are compared, interpreted and a recommendation on the optimal renovation strategy is stated.    

The optimal renovation strategy is found in a high- quality refurbishment of the thermal envelope by including prefabricated façade elements to the thermal envelope which include solar thermal collectors as well as photovoltaic panels. In terms of environmental indicators this renovation will always be beneficial due to its lowest impact. Also, a change of energy supply to district heating is beneficial for all construction standards and should be implemented on all future renovations. Additionally, the sensitivity analysis on the high- quality strategy determined that a surplus of electricity production by increase of PV area is not feasible as the operational impact reacts very sensible to a change of the electricity mix to more renewable resources (feature of the included sensitivity analysis).  Especially for plus-energy buildings it is therefore necessary to find the optimum balance between diminishing returns due to the changes in energy mixes and financial investment over the entire lifetime of the building.

This study identifies the benefits gained by a high- quality refurbishment and analyses its robustness based on future scenarios. As there is an urgent need of refurbishing a large share of our building stock in a short period of time in order to reduce the global emissions by 80% by 2050, the stated renovation strategy with a high degree of prefabrication would represent a major step towards achieving these targets.