Aoife Houlihan Wiberg

Net-zero buildings: incorporating embodied impacts

The design and assessment of net-zero buildings commonly focus exclusively on the operational phase, ignoring the embodied environmental impacts over the building life cycle. An analysis is presented on the consequences of integrating embodied impacts into the assessment of the environmental advantageousness of net-zero concepts. Fundamental issues needing consideration in the design process – based on the evaluation of primary energy use and related greenhouse gas emissions – are examined by comparing three net-zero building design and assessment cases: (1) no embodied impacts included, net balance limited to the operation stage only; (2) embodied impacts included but evaluated separately from the operation stage; and (3) embodied impacts included with the operation stage in a life cycle approach. A review of recent developments in research, standardization activities and design practice and the presentation of a case study of a residential building in Norway highlight the critical importance of performance indicator definitions and system boundaries. A practical checklist is presented to guide the process of incorporating embodied impacts across the building life cycle phases in net-zero design. Its implications are considered on overall environmental impact assessment of buildings. Research and development challenges, as well as recommendations for designers and other stakeholders, are identified.

Life cycle emissions analysis of two nZEB concepts

The net-zero emissions building (nZEB) performance is investigated for building operation (EO) and embodied emissions in materials (EE) for Norways 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 buildings life. The main drivers for the CO2 equivalent (CO2e) emissions are revealed for both building concepts through a detailed emissions calculation. The influence of the CO2e factor for electricity is emphasized and it is shown to have significant impact on the temporal evolution of the overall CO2e emissions balance. The results show that the criterion for zero emissions in operation is easily reached for both nZEB concepts (independent of the CO2e 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.

Industry- and Research-driven Education in Sustainable Architecture: Transitioning Towards a Professional M.Sc. Programme on Zero Emission Built Environments

“A project is a vehicle to bring about change” [1] Strong pressure from industry, students and society has led the Norwegian University of Science and Technology (NTNU) in Trondheim to introduce a 2-year international, interdisciplinary M.Sc. program in Sustainable Architecture in fall 2010. The program expanded from a 1-semester specialization course in energy- and environment-friendly architecture (22.5 ECTS) to a 120-ECTS 2-year program of four consecutive semesters. All courses within the program can also be selected as independent topics by regular architecture students who only want to specialize in low-carbon architecture during one semester. The program is connected to the Norwegian Centre for Environment-friendly Energy Research (CEER) in Zero Emission Buildings which was created under the leadership of NTNU (Director) and SINTEF (CEO) in 2009 [2]. The ZEB centre works closely with educational and research institutions, industry and public administration in Norway and abroad. The collaboration en...

Life Cycle GHG Emissions from a Wooden Load-Bearing Alternative for a ZEB Office Concept

A major contributor to global greenhouse gas emissions is the production of concrete and steel for the construction industry IPCC (2007). To combat global warming, innovative solutions are needed in the construction industry to reduce emissions from both energy and material use in buildings. In a previous study the first phase of a GHG emissions analysis for a Norwegian ZEB office concept was presented. The aim of which was to achieve a zero emission balance where operational and material emissions are accounted for ZEB OM. The results from the first phase showed that the load bearing system accounted for a large share of the embodied emissions. In addition, the ZEB OM ambition level was not met, thus emphasizing the need for further work on alternative solutions and material choices. This paper presents the results of a comparative study between this original office concept study and a predominantly wooden alternative loadbearing structure consisting of wood trusses, glue laminated beams and columns. The wooden alternative is comparable since it has been dimensioned to fulfil the same technical requirements for bearing capacity, sound and fire resistance. In addition, the system boundary was extended to include three alternative end-of-life scenarios. It was found that the wooden alternative structure almost halved the emissions compared to the original concrete and steel ZEB office concept model. This trend is the same in the cradle to gate and all three end-of life scenario’s. The analysis clearly shows that emissions from the production process outweigh any emissions from the material’s end-of-life treatment. This means that the material choice plays a major role in embodied emissions, as well as it being crucial to reduce the required construction material quantity.