Life-cycle environmental and economic assessment of nearly zero-energy buildings: a case study in Norway

Buildings are responsible for several environmental impacts, e.g., high energy use and greenhouse gas emissions, during the whole life cycle. The reduction of such negative impacts can nowadays be boosted through the adoption... [ view full abstract ]

Buildings are responsible for several environmental impacts, e.g., high energy use and greenhouse gas emissions, during the whole life cycle. The reduction of such negative impacts can nowadays be boosted through the adoption of energy efficiency measures for the new and existing building stock. Latest trends have focused on passive houses and zero-energy buildings (ZEBs), which have been discussed in the energy policies of several countries. For instance, the recast of the EU Directive on Energy Performance of Buildings (EPBD) states that all new buildings should be nearly ZEBs (nZEBs) by 2020.

The construction of nZEBs is significant in the context of the Sustainable Development Goals, as it is not only associated to environmental benefits but also to economic and social advantages, such as the reduction of utility bills and the generation of new jobs. Furthermore, nZEB projects can represent a significant source of business for the stakeholders involved in the entire building process.

In the last years, specific methodologies have been employed for the environmental and economic evaluation of buildings throughout the life cycle, e.g., life cycle assessment (LCA) and life cycle cost (LCC) analysis. Several case studies have already been analyzed, including nZEBs, although such methodologies are more often implemented independently than jointly.

Further analyses on the combined environmental and economic impacts of nZEBs are therefore needed towards a better understanding of their overall sustainability performance. Moreover, a discussion on the possible integration of sustainability analyses into the business models of nZEB projects would be useful, given the gaps in the current research and practical approaches.

This research work shows the outcomes of the application of the LCA and LCC methodologies on a specific case study in Norway. Several performance indicators, i.e., global warming potential (GWP), cumulative energy demand (CED), and net present cost (NPC), have been assessed for a nZEB recently built for the Norwegian Defense Estates Agency. These indicators have been computed for the project as built and for some alternatives that include different solutions for materials and technical systems.

The results confirm the significance of the construction phase for both the environmental and economic impacts in nZEBs. In particular, the alternatives with the highest use of wood as building material have the lowest GWP and NPC values, while the alternative with the highest use of photo-voltaic panels has the lowest CED.

The findings of this research work might be used in the decision-making context for the assessment of the environmental and economic impacts of different solutions in nZEBs. Furthermore, the results might be useful for both academics and practitioners who are interested in nZEBs and would like to increase their knowledge about the combined environmental and economic performance of such buildings.