Green roofs are complex systems, with a vegetation layer covering the outermost surface of the building shell. An effective design may confer environmental and energy benefits. Most field studies evaluating green roof performance have been conducted in warmer climates with few studies of full-scale green roofs in cold regions. No study has so far evaluated the energy performance of a green roof in a sub-arctic climate. This study demonstrates the heat flow and thermal effect of an extensive green roof versus a black bare roof area on a highly insulated building in the sub-arctic town of Kiruna, Sweden, for the period from November 2016 to February 2018. Measured temperature and heat flux values were consistently higher and more variable for the black roof than the green roof, except during the snow-covered winter months when the responses were similar. The cumulative heat flux showed that the net heat loss was greater through the black than the green roof, but the values remained low. Overall, the study confirms that the energy benefit of a green roof on a highly insulated building in a subarctic climate is low.

Green roofs are complex technology systems, adopting a vegetation layer on the outermost surface of the building shell. A proper design implement environmental and energy benefits. Green roof are aimed to reduce roof temperature and thus the summer solar gains, without worsening the winter energy performance. Most studies evaluating green roof performance have been conducted in warmer climates. There are very limited studies of green roofs in cold climate. Some research has investigated the thermal effect of the snow layer on green roof. But no study has so far evaluated the energy performance of green roof in sub-arctic climate. This study evaluates the heat flow and thermal effect on a green roof situated on a passive house building in the sub-arctic town Kiruna, Sweden for a period from 25th of October—4th of January. The ongoing measurements of temperature and heat flux is done on an extensive green roof and compared to the same roof covered solely by a roofing felt layer. The fluctuation in temperature was consistently higher for the roof with the roofing felt layer than for the green roof. But the surface temperature of both roofs was getting more and more align as the roofs are covered by snow during November and December. However during December month the green roof had a higher heat flux out of the building compared to the black roof.

As the operational energy use in buildings contributes highly to the total energy used and greenhouse gases emitted in the cold climate regions of Europe, buildings which are more energy-efficient and less carbon-intensive during operation are key to meet sustainability objectives in these regions. Yet, research shows that the practice of passive or low-energy buildings in the sub-arctic climate of northern Sweden is comparatively less than in the southern region. Moreover, previous studies did not explicitly examine the performance of low energy buildings in sub-arctic climate in relation to established building energy efficiency standards. Consequently, knowledge regarding the energy performance of low-energy buildings in such climate is limited. Therefore, the aim is to evaluate the performance, in terms of indoor temperature and energy use for heating, domestic hot water and electricity of a new-built passive house titled “Sjunde Huset” in the sub-arctic town of Kiruna. It is Sweden’s northernmost house designed to fulfil the Swedish passive-house criteria of a maximum heat loss factor of 17 W/m2 and a maximum annual energy use of 63 kWh/m2. The implemented passive design strategies include a highly insulated, compact and airtight building envelope with a vestibule, mechanical ventilation with heat recovery and renewable energy production through photovoltaic solar cells. The house is connected to district heating and is equipped with energy-efficient appliances to allow low occupant energy use. Ongoing performance evaluation is based on building simulation and measurements of energy and temperature in different zones of the building. Energy performance deviations between occupied and non-occupied zones are explored through internal heat gain evaluations. The indoor temperature is also evaluated to assess the temperature variations throughout the year. The ongoing research further evaluate a comparative simulated and measured energy analysis of heating, hot water and electricity based on both the international passive house standard and the Swedish passive house criteria “Feby 12”.

Evaluation of carbon impacts during building design has for too long unilaterally focused on the operational carbon impacts through the application of Energy Efficiency Measures (EEMs), e.g. enhancing the thermal resistance of the building envelope by using additional insulations, Window to Wall Ratio (WWR) etc. Research indicates that there is a need to also include the embodied carbon impacts and optimizing the trade-off between embodied and operational carbon impacts. Multi-objective optimization approaches can be a solution for handling this trade-off. Therefore, a previously developed BIM-based multi-objective optimization approach has been extended to also cover the impact of the carbon footprint. The extended optimization approach was then tested in a case study of a multifamily residential building located in Stockholm to find the optimal design solutions of the embodied versus operational carbon impact trade-off. The results of the case study demonstrate the applicability of the extended approach in handling the trade-off problem and aiding in more environmentally friendly decisions during the design process.

Assessment of the embodied energy associated with the production and transportation of materials during the design phase of building provides great potential to profoundly affect the building’s energy use and sustainability performance. While Building Information Modeling (BIM) gives opportunities to incorporate sustainability performance indicators in the building design process, it lacks interoperability with the conventional Life Cycle Assessment (LCA) tools used to analyse the environmental footprints of materials in building design. Additionally, many LCA tools use databases based on industry-average values and thus cannot account for differences in the embodied impacts of specific materials from individual suppliers. To address these issues, this paper presents a framework that supports design decisions and enables assessment of the embodied energy associated with building materials supply chain based on suppliers’ Environmental Product Declarations (EPDs). The framework also integrates Extract Transform Load (ETL) technology into the BIM to ensure BIM-LCA interoperability, enabling an automated or semi-automated assessment process. The applicability of the framework is tested by developing a prototype and using it in a case study, which shows that a building’s energy use and carbon footprint can be significantly reduced during the design phase by accounting the impact of individual material in the supply chain.

Today, climate change is an issue of great concern. In addition, the building sector is considered to be one of the major energy users causing considerable amount of greenhouse gas emissions. Although, energy-efficient buildings are built today that use low amount of energy during operation, the embedded energy from construction and production of building material can still be relatively high. This paper focuses on the application of Building Information Modeling (BIM) using Environmental Product Declaration (EPD) to assess the environmental impacts from building materials and production to enable the designers to make environmentally friendlier decisions. Toward this approach, we propose a model which is examined in a case study of a roof structure on a commercial building which was constructed by off-site prefabricated roof-elements. As a result, the feasibility of the proposed model is appreciated in the assessment of the carbon footprint and embodied energy of the building materials and components. The proposed model needs to be further developed regarding the specification of the materials and components to make the information exchange between the BIM model and EPD in the environmental assessment of the building design more practicable.

Reducing the energy consumption of buildings is an important goal for the European Union. However, it is therefore of interest to investigate how different member states address these goals. Countries like Sweden and Germany have developed different strategies for energy conservation within the building sector. A longitudinal comparison between implemented energy conservation key policy instruments in Sweden and Germany and a survey regarding the management of energy requirements in the building process shows that:– No evidence is found that energy consumption is of great importance for producing competitive offers, either for Swedish or German clients.– The Swedish market-driven policy has not been as successful as the German regulation policy in decreasing the energy consumption of new buildings.– Building standards and regulations regarding energy performance affects how professionals are educated and the way energy requirements and demands are managed throughout the building process.In conclusion, the client's demand will govern the development of energy efficient buildings. Therefore, in order to use market-driven policies, the desired parameters must be of concern for the customer to influence the majority of building projects to be more energy efficient than is specified in national standards and regulations.

From a sustainable development perspective, buildings should be designed to be as energy-efficient as possible, as the contribution of buildings to total energy consumption has steadily increased, reaching between 20% and 40% in the developed countries. One of the main challenges for achieving this goal is to develop more cost-effective systems and processes for energy renovation and modernising of the building stock of Europe. This challenge is addressed in this thesis. The research presented herein has had the overall purpose to identify and explore obstacles in the design process of constructing more energy-efficient buildings. Three research questions have guided the research work: (1) How can life cycle cost be used to predict the cost benefits of energy efficient buildings?; (2) How can the handling of energy performance requirements in the design process for buildings be improved?; (3) How do client requirements, political governance and regulations affect the design of energy performance in buildings? The research is based on literature reviews, interviews and surveys, as well as case and computational studies. A computational study was performed with three different building types situated in Finland using three different energysaving design concepts for each building. Energy consumption and construction costs were analysed for each case and the financial viability was analysed using the discounted payback method. Individual interviews were carried out to determine to what extent life cycle cost calculations are used in the construction sector and how energy performance is taken into account in model-based design processes for buildings. A decision-making framework and an axiomatic design model for a performance-based design process was then developed and the conceptual model was compared with a real case of low energy design in Sweden. Finally, a survey explored energy conservation strategies in the design of buildings in Germany and Sweden and a longitudinal investigation of key policy instrument regarding energy conservation in Germany and Sweden was conducted to support the main findings of the survey. The main results of the research work show that: * There is no evidence that the design of energy performance is considered differently in the design process for buildings in Sweden and Germany, even if regulations and building codes differ between the two countries. However, the somewhat steeper reduction in space heating in Germany compared with Sweden could be due to the stricter regulation in the building codes in Germany over the last decade. * The transparency of the design and the associated decision-making about energy performance can be improved by using the requirement management model developed, which is based on axiomatic principles and the proposed decision-making framework for evaluating, structuring and detailing the requirements from the conceptual to the detailed design stages. * Energy performance design can give cost benefits over a specific time for a building, as measured by the resulting life cycle costs. In general, life cycle cost analysis can be a tool for evaluating cost benefits over time and provide support for the decision-makers, but the challenges and uncertainties of its use have to be taken into account in the decision-making process. To conclude, the "energy gap" between regulations and what is technologically possible can be reduced to a certain extent by facilitating the energy design process with a performance-based design process and decision-making tools that support the evaluation of life cycle performance. However, it seems that regulation is a more important driver for the development of technology for low energy housing than market forces so the regulatory limit should therefore be set with respect to what is possible and not with respect to current practice.

The economic viability of novel energy-efficient design concepts has been evaluated in Finnish educational buildings. The total energy consumption of representative target buildings with each design concept has been found using the whole-building simulation tool IDA Indoor Climate and Energy 4.0, and the financial viability has been assessed using the discounted payback period method. Different thermal insulation and air tightness properties of the building envelope, and different ventilation's heat recovery efficiency assumptions and heat distribution options have been investigated. The results suggest that a prudent attitude should be taken toward the investments in ultra-low-energy designs. Total energy-saving potential of 25-32% can be obtained. The payback periods varied from 15 to more than 40 years. The results can be generalized in cold climates and techno-economic conditions similar to Finland