The paper aims to investigate whether it is possible to achieve a net Zero Emission Building (nZEB) by balancing emissions from the energy used for operation and embodied emissions from materials with those from on-site renewables in the cold climate of Norway. The residential nZEB concept is a so-called all-electric solution where essentially a well-insulated envelope is heated using a heat pump and where photovoltaic panels (PV) production is used to achieve the CO_2eq balance. In addition, the main drivers for the emissions are revealed through the CO_2eq calculation for a typical Norwegian, single-family house. This concept building provides a benchmark rather than an absolute optimum or an architectural expression of future nZEBs. The main result of this work shows that the criteria for zero emissions in operation (ZEB-O) is easily met, however, it was found that the only use of roof mounted PV production is critical to counterbalance emissions from both operation and materials (ZEB-OM). The results show that the single-family house has a net export to the electric grid with a need for import only during the coldest months. In the next stage of the work, the concept will be further optimised and the evaluation method improved.

In order to reach the goal of a zero emission building (ZEB), CO2 emission data has to be made available and verified for traditional building materials, new ‘state-of-the-art’ building materials and the active elements used to produce renewable energy. However, an initial literature review found that although there are databases of embodied carbon values for most building materials, the range in results for some materials are varied and inconsistent.

This paper follows on from previous work on the development of a transparent and robust method to calculate CO2eq emissions of the materials used in the concept analysis of the ZEB residential model, single family house. The aim of the concept analysis was to investigate if it was possible to achieve an "all-electric" ZEB-building by balancing operational and embodied emissions by PV-production on the building. The analysis has not considered minimising the embodied emissions but is rather a documentation of the embodied carbon dioxide emissions using traditional materials in the envelope and in the ventilation and heating systems, as well as, those associated with the renewable energy system, such as the photovoltaic panels and solar thermal collectors. Material inventories have been imported from the Revit BIM model, via MS Excel. The material inputs are structured according to the Norwegian table of building
elements, NS 3451-2009 and emission factors (kgCO2eq per functional unit) for the calculations are sourced from SIMAPRO/ Ecoinvent version 2.2.

The goal of these calculations is to estimate, and thus provide an overview of the materials and components in the ZEB residential model, which contribute the most to the embodied carbon dioxide emissions. The calculations are based on the principles of environmental assessment through life cycle analysis. It should be noted that in this first round of calculations, not all life cycle phases are included. In the next stage of the calculations, the model will be optimised and the impact on emissions recalculated accordingly

The main aim of the work has been to do modeling and calculations of the energy use, embodied emission and the total CO2-emission for a typical Norwegian residential building. By doing this we try to reveal and study the main drivers for the CO2-emission, and also which performance is necessary for components and solutions in a Zero Emission Building according to the current Norwegian ZEBdefinition.

Moving away from the annual energy budget and including the emissions of the entire building lifetime during construction, operation, and disposal is a key aspect of ZEB. This can be summarised in an emission inventory of operation and building components and services. The aim of this paper is to investigate the emission balance of both operational and the embodied energy in different highly energy efficient buildings concepts which are worth considering toward achieving Zero emission buildings. In this work four concepts for energy efficient buildings are identified which could provide stepping stones towards a definition of ZEB. These concepts were applied to a generic model (´shoe box model´) of a detached house. The greenhouse gas emissions in kilogrammes CO2 equivalents over buildings lifetime due to embodied and operational energy were accounted for three possible approaches towards achieving a Zero Emission Building. A reference building was used as a base case which is a passive house with reference materials used in the commonly used Norwegian construction. The first alternative aims at zero operational energy disregarding the embodied energy in the materials. The second alternative tries to reduce the embodied energy based on \'low emission\' material choice, without efforts to improve the energy performance. Alternative three combines both measures from alternative 1 and 2. When applying the UCTE electricity mix, representing the present electricity infrastructure, clearly most emissions are related to operation. Therefore alternatives 1 and 2 without operational emissions have significantly lower emissions. Applying other electricity mix representing a de-carbonised electricity grid, the differences are less distinct. And since electricity is also part of the emissions of building materials as electricity factor for the production the results might align even more. Hereby also the location of production gains increased importance. Windows, foundations, slab to ground, floor slabs of the building components and sanitary installation, ventilation system of the building services show high emissions in all four cases. Two main reasons can be identified – lifetime and emission-intensive materials. Lifetimes of components and services have a crucial impact and must be defined clearly. Especially windows and building services have short individual lifetimes and require replacement when considering the entire building\'s lifetime. The use of the same material or unit may lead to an overestimation of emissions. However, the prediction and application of ´better´ future products and lower emissions due to improved production and a de-carbonised energy supply appears problematic. More important might be the handling of the replaced items. Cradle-to-gate conditions do not allow an appropriate treatment in this case.