Abstract

The net-zero emissions building (nZEB) performance is investigated for building operation and embodied emissions in materials for Norway’s cold climate. An nZEB concept for new residential buildings was developed in order to understand the balance and implications between operational and embodied emissions over the building’s life. The main drivers for the CO2 equivalent (CO2eq) emissions were revealed for the building concept through a detailed emissions calculation.
Previous investigations showed that the criterion for zero emissions in operation is easily reached by the nZEB concept (independent of the CO2eq factor considered). Nevertheless, embodied emissions from materials appeared significant compared to operational emissions. It was found that an overall emissions balance, including both operational and embodied energy, is difficult to reach and would be unobtainable in a scenario of low carbon electricity from the grid i.e. low CO2eq factor for electricity. In order to make these conclusions robust, a sensitivity analysis was performed on the dominant sources of CO2eq emissions, as well as, on how it impacts the emission balance during the building lifetime. In the baseline work, embodied emissions were evaluated using the EcoInvent database in order to get a consistent life cycle assessment (LCA) method for all the building materials. The first step of this sensitivity analysis is therefore performed to compare embodied emissions when specific Norwegian Environmental Product Declarations (EPD) were used instead of generic data from EcoInvent thus making data more representative for the Norwegian context. In addition, the photovoltaic (PV) system, which supplies renewable electricity to the building, also contributes significantly to the embodied emissions. The second step of the analysis evaluates different PV system design options in order to find the one with highest net emissions reduction. Finally, since the building concept was based on a highly-insulated building envelope, the dominant source of emissions during building operation turned out to be electric appliances. The third step of the analysis thus discusses the energy consumption of electric appliances and how it could be reduced through more efficient products, especially the so-called hot-fed machines (i.e. washing machines, tumble dryer and dishwasher).

Abstract

The ambition level for the zero emission neighbourhood Aadland is that the area will be self supplied with both thermal and electric energy. This paper presents how emissions from operation of the 500 dwellings are offset by on-site renewable energy production. The paper also describes a procedure for how to deal with embodied emissions from materials in an early stage design phase. The study verifies that it is possible to reach a zero emission balance for the neighbourhood. Zero emission from operation is achievable as an average for the neighbourhood. For individual zero emission buildings this also includes embodied emissions from materials and construction in a lifecycle perspective. Qualitative requirements for emissions from materials are defined for all buildings in the neighbourhood.

Abstract

The net-zero emissions building (nZEB) performance is investigated for building operation (EO) and embodied emissions in materials (EE) for Norway's cold climate. nZEB concepts for new residential and office buildings are conceived in order to understand the balance and implications between operational and embodied emissions over the building's life. The main drivers for the CO₂ equivalent (CO_2e) emissions are revealed for both building concepts through a detailed emissions calculation. The influence of the CO_2e factor for electricity is emphasized and it is shown to have significant impact on the temporal evolution of the overall CO_2e emissions balance. The results show that the criterion for zero emissions in operation is easily reached for both nZEB concepts (independent of the CO_2e factor considered). Embodied emissions are significant compared to operational emissions. It was found that an overall emissions balance including both operational and embodied energy is difficult to reach and would be unobtainable in a scenario of low carbon electricity from the grid. In this particular scenario, the net balance of emissions alone is nonetheless not a sufficient performance indicator for nZEB.

This report deals with how to define what a Zero Emission Building (ZEB) is with explanation and analysis of different parameters related to embodied emissions of CO₂ equivalents. The report can be used as a guidance tool on how to assess embodied emissions, and also on what parameters should be evaluated in such an assessment.

Different ambition levels for ZEBs may include life stages, operation, material, construction and end-of-life and can be documented according to EN 15978. Calculation procedures should include system boundaries, embodied emissions from materials, transport, the construction process and waste handling according to the ambition level. CO_{2 eq} emissions factors, service life estimates and payback scenarios for CO₂ emissions need to be considered.

The report does not contain one single clearly defined method, but rather a state-of-the-art summary on the different issues and refers to other relevant national and international work in the field of ZEB definitions. The issues presented here are in early stages of development and will need to be verified and further developed.