Swedish Building Research Articles

Transforming a residential building cluster into electricity prosumers in Sweden: Optimal design of a coupled PV-heat pump-thermal storage-electric vehicle system

Smart grid is triggering the transformation of traditional electricity consumers into electricity prosumers. This paper reports a case study of transforming an existing residential cluster in Sweden into electricity prosumers. The main energy concepts include (1) click-and-go photovoltaics (PV) panels for building integration, (2) centralized exhaust air heat pump, (3) thermal energy storage for storing excess PV electricity by using heat pump, and (4) PV electricity sharing within the building cluster for thermal/electrical demand (including electric vehicles load) on a direct-current micro grid. For the coupled PV-heat pump-thermal storage-electric vehicle system, a fitness function based on genetic algorithm is established to optimize the capacity and positions of PV modules at cluster level, with the purpose of maximizing the self-consumed electricity under a non-negative net present value during the economic lifetime. Different techno-economic key performance indicators, including the optimal PV capacity, self-sufficiency, self-consumption and levelized cost of electricity, are analysed under impacts of thermal storage integration, electric vehicle penetration and electricity sharing possibility. Results indicate that the coupled system can effectively improve the district-level PV electricity self-consumption rate to about 77% in the baseline case. The research results reveal how electric vehicle penetrations, thermal storage, and energy sharing affect PV system sizing/positions and the performance indicators, and thus help promote the PV deployment. This study also demonstrates the feasibility for transferring the existing Swedish building clusters into smart electricity prosumers with higher self-consumption and energy efficiency and more intelligence, which benefits achieving the ‘32% share of renewable energy source’ target in EU by 2030.

Planning and operation of an integrated energy system in a Swedish building

More flexibility measures are required due to the increasing capacities of variable renewable energies (VRE). In buildings, the integration of energy supplies forms integrated energy systems (IES). IESs can provide flexibility and increase the VRE penetration level. To upgrade a current building energy system into an IES, several energy conversion and storage components are needed. How to decide the component capacities and operate the IES were investigated separately in studies on system planning and system operation. However, a research gap exists that the system configuration from system planning is not validated by actual operation conditions in system operation. Meanwhile, studies on system operation assume that IES configurations are predetermined. This work combines system planning and system operation. The IES configuration is determined by mixed integer linear programming in system planning. Actual operation conditions and forecast errors are considered in system operation. The actual operation profiles are obtained through year-round simulations of different energy management systems. The results indicate that the system configuration from system planning can meet energy demands in system operation. Among different energy management systems, the combination of robust optimization and receding horizon optimization achieves the lowest yearly operation cost. Meanwhile, two scenarios that represent high and low forecast accuracies are studied. Under the high and low forecast accuracy scenarios, the yearly operation costs are about 4% and 6% higher than that obtained from system planning.

Primary energy and CO2 emissions implications of different insulation, cladding and frame materials for residential buildings

In this study, we analyse and compare the primary energy use and carbon dioxide (CO2) emissions associated with different insulation, cladding and frame materials for a constructed concrete frame multi-storey residential building in Sweden. Our approach consists of identifying individual materials giving the lowest primary energy use and CO2 emissions for each building envelope part and based on that, modelling different material combinations to achieve improved alternatives of the concrete frame building with the same operation energy use based on the Swedish building code or passive house criteria. We analyse the complete materials and energy chains, including material losses as well as conversion and fuel cycle losses. The analysis covers the primary energy use to extract, process, transport, and assemble the materials and the resulting CO2 emissions to the atmosphere. The results show wide variations in primary energy and CO2 emissions depending on the choice of building envelope materials. The materials for external walls contribute most to the primary energy and CO2 emissions, followed by foundation, roof and external cladding materials. The improved building alternatives with wood construction frames, wood external cladding, expanded polystyrene as foundation insulation and cellulose insulation in the external walls and roof result in about 36 - 40% lower production primary energy use and 42 – 49% lower CO2 emissions than the improved concrete alternative when achieving the same thermal performance. This study suggests that strategies for low-energy buildings should be combined with resource-efficient and low carbon materials in the production phase to mitigate climate change and achieve a sustainable built environment.

Energy Renovation versus Demolition and Construction of a New Building—A Comparative Analysis of a Swedish Multi-Family Building

This study addresses the life cycle costs (LCC) of energy renovation, and the demolition and construction of a new building. A comparison is made between LCC optimal energy renovations of four different building types with thermal performance, representing Swedish constructions from the 1940s, 1950s, 1960s, and 1970s, as well as the demolition of the building and construction of a new building that complies with the Swedish building code. A Swedish multi-family building from the 1960s is used as a reference building. LCC optimal energy renovations are identified with energy saving targets ranging between 10% and 70%, in addition to the lowest possible life cycle cost. The analyses show that an ambitious energy renovation is not cost-optimal in any of the studied buildings, if achieving the lowest LCC is the objective function. The cost of the demolition and construction of a new building is higher compared to energy renovation to the same energy performance. The higher rent in new buildings does not compensate for the higher cost of new construction. A more ambitious renovation is required in buildings that have a shape factor with a high internal volume to heated floor area ratio.

Numerical Simulations and Empirical Data for the Evaluation of Daylight Factors in Existing Buildings in Sweden

Point Daylight Factor (DFP) has been used for daylighting design in Sweden for more than 40 years. Progressive densification of urban environments, in combination with stricter regulations on energy performance and indoor environmental quality of buildings, creates complex daylight design challenges that cannot be adequately solved with DFP. To support a development of the current and future daylight indicators in the Swedish context, the authors have developed a comprehensive methodology for the evaluation of daylight levels in existing buildings. The methodology comprises sample buildings of various use and their digital replicas in 3D, detailed numerical simulations and correlations of diverse DF metrics in existing buildings, a field investigation on residents’ satisfaction with available daylight levels in their homes, and a comparison between the numerical and experimental data. The study was deliberately limited to the evaluation of DF metrics for their intuitive understanding and easy evaluation in real design projects. The sample buildings represent typical architectural styles and building technologies between 1887 and 2013 in Gothenburg and include eight residential buildings, two office buildings, two schools, two student apartment buildings, and two hospitals. Although the simulated DFP is 1.4% on average, i.e., above the required 1%, large variations have been found between the studied 1200 rooms. The empirical data generally support the findings from the numerical simulations, but also bring unique insights in the residences’ preferences for rooms with good daylight. The most remarkable result is related to kitchens, typically the spaces with the lowest DF values, based on simulations, while the residents wish them to be the spaces with the most daylight. Finally, the work introduces a new DF metric, denoted DFW, which allows daylighting design in early stages when only limited data on the building shape and windows’ arrangement are available.

Transition governance for energy efficiency - insights from a systematic review of Swedish policy evaluation practices

BackgroundThe transition towards a more sustainable energy system is urgent for addressing global environmental and social challenges, and will require transformative changes including improved energy efficiency in the built environment. To reach identified efficiency potentials, various policy instruments have been introduced but their effects are often unclear. In this paper, we argue that the outline of transformative policy strategies will require well-designed evaluations. The objective is to present a theory-based evaluation framework that can be used to assess existing evaluations, in order to support transformative policy strategies. The framework is also applied to provide insights from current Swedish evaluation practices.MethodsThe theory-based evaluation framework presented builds on evaluation theory, policy analysis and transition research and is arranged around methods, value judgements and use of the evaluations. Moreover, key aspects from transition research are included to provide guidance for transformative efforts in the evaluations. The systematic review presented in the paper is qualitative, covering 33 policy evaluations for energy efficiency in buildings in Sweden, commissioned by Swedish governmental authorities over a decade.ResultsThe results of the review reveal a wide range of evaluations undertaken, using a sound methodological evaluation base that builds on a variety of methods for analysis, and application of multi-criteria analyses. Commonly, however, a rather narrow scope was applied and we note a missed opportunity for triangulation of findings. Key aspects for capturing transformative efforts, such as system-, scale- and multi-actor approaches, as well as visioning, experimentation and learning, were considered to varying extents, but could be more explicit and elaborate.ConclusionIn all, we find the proposed theory-based evaluation framework useful for assessing and discussing both robustness and transformative efforts of current policy and evaluation practices. The review of the Swedish policy evaluations further indicates sound evaluation practices, and a foundational structure for identifying and analysing transformative efforts. To fully support transformative changes, we suggest a wider system perspective and a more thorough multi-actor approach and actor involvement in the evaluations. We also stress the need to further link evaluation theory with transition research to design evaluations that can support transformative changes in society.

Twelve Years of Energy Efficiency in Historic Buildings in Sweden

Abstract The Swedish National Research programme for Energy Efficiency in historic buildings was initiated in 2006 by the Swedish Energy Agency. This article gives an overview of the programme: objectives, projects and the general results of the programme. The research programme aims to develop knowledge, methods and technical solutions that contribute to energy efficiency in historically valuable buildings without destroying or damaging the historical value of the buildings, including decoration, furnishings, interiors or equipment. The programme is not limited to listed and monumental buildings but covers a wider range of historic buildings that account for a large part of the energy use in the building sector. For one and two-family houses, around 25 % of the energy use is associated with buildings built before 1945. The same number for multifamily houses is around 15 %. The programme is currently in its third consecutive four-year-stage. Previous four-year-stages were completed in 2010 and 2014. Over time, the scope of the programme and the projects have developed from mainly dealing with indoor climate control in monumental buildings towards addressing more general issues in the much larger stock of non-listed buildings. Technical research, based on quantitative analysis, dominate throughout all three stages, however most projects have had interdisciplinary components. The results from the programme have been presented in 31 journal papers, 67 conference papers, five books and five PhD theses. The projects have also contributed to CEN standards and resulted in a number of Bachelors and Master’s theses. An equally important long-term effect of the programme is that the number of Swedish researchers in the field have increased from practically none in 2007 to 18 senior researchers and twelve PhD students from ten universities in 2014. The research programme on Energy Efficiency in historic buildings is unique in an international context. Hopefully it can serve as an example for other countries on how to address an important interdisciplinary research challenge.

Numerical and Experimental Study on Modular-Based Timber Structures

Building with prefabricated light-frame volume modules is a prevalent and innovative construction method for low and mid-rise timber buildings. Compared to traditionally site-built constructions this method is very advantageous due to its high prefabrication level and the fast on-site assembly of the modules. The focus of this project is to study and optimise the global shear stiffness of the volume modules and to secure a large enough shear and uplift stiffness of the mechanical (or friction based) connections between the modules. Some companies assume that the friction between the modules is sufficient to transfer the wind stabilization forces down through the entire building. Regarding structural safety, connection design is an important task that needs to be numerically studied and experimentally verified. The paper presents numerical and experimental results obtained from two ongoing research projects concerning modular-based timber buildings in Sweden. The final aim of this work is to develop an efficient three dimensional finite-element model to analyse both the global and detailed structural behaviour of these types of buildings. To study the overall shear stiffness of the volume modules, eight different test-modules are to be tested. The test results will be used to calibrate the numerical model.

A development process for extending buildings vertically – based on a case study of four extended buildings

PurposeThe purpose of the study, upon which this paper is based, was to contribute an improved understanding of the vertical extension of buildings, by presenting a development process for its implementation in which the key aspects to consider when planning such extensions are highlighted.Design/methodology/approachThe approach is based on linking the diffusion of innovation together with case study research to stimulate further development in vertically extending buildings. Four cases of vertically extended buildings in Sweden were selected for the study.FindingsThe development process highlights seven key areas for decisions when planning a vertical extension. These areas are: opportunities for vertical extension; strategies for implementation; detailed planning process; concept development; evaluation; building permit; and procurement. The development processes and lessons learnt from each case are presented, covering both success and failure.Research limitations/implicationsThe research is based on four cases of vertically extended buildings. The findings offer valuable insights into the development process which should provide the research community with an improved understanding of the challenges faced.Practical implicationsThe findings will help planners, housing owners, housing developers and facility managers better understand the conditions that favour successful implementation of vertical extensions.Originality/valueThe paper provides the reader with an understanding of the challenges faced in the vertical extension of a building and the means of overcoming them to create a simplified development process.

Review of Constructions and Materials Used in Swedish Residential Buildings during the Post-War Peak of Production

One of the greatest challenges for the world today is the reduction of greenhouse gas emissions. As buildings contribute to almost a quarter of the greenhouse gas emissions worldwide, reducing the energy use of the existing building stock is an important measure for climate change mitigation. In order to increase the renovation pace, there is a need for a comprehensive technical documentation that describes different types of buildings in the existing building stock. The purpose of this study is to analyse and describe existing residential buildings in Sweden. The data are based on published reports from 1967 to 1994 that have not been publicly available in a database for other researchers to study until now. Data from the reports have been transferred to a database and analysed to create a reference for buildings and/or a description of building typology in Sweden. This study found that there is a rather large homogeneity in the existing residential building stock. However, it is not possible to use a single reference building or building technique to cover the majority of the existing buildings. In Sweden, common constructions for exterior walls in multi-dwelling buildings which should be used for further studies are insulated wood infill walls with clay brick façades, lightweight concrete walls with rendered façades and concrete sandwich walls. The most common constructions for one- and two-dwelling buildings are insulated wooden walls with clay brick façades or wooden façades. Furthermore, roof constructions with insulated tie beam and roof constructions where the tie beam is a part of the interior floor slab are frequently used and should be included in further studies.

Evaluation of thermal comfort in a historic building refurbished to an office building with modernized HVAC systems

ABSTRACTEnvelopes with low thermal performance are common characteristics in European historic buildings, causing higher energy demand and insufficient thermal comfort. This paper presents the results of a study on indoor environmental quality (IEQ), with special focus on thermal comfort, in the historic City Hall of Gävle, Sweden, now used as an office building. There are two modern heat recovery ventilation systems with displacement ventilation supply devices. The district heating network heats the building via pre-heat supply air and radiators. Summer cooling comes from electric heat pump ejecting heat into the exhaust ventilation air. A building management system (BMS) controls the heating, ventilation and air-conditioning (HVAC) equipment. The methodology included on-site measurements, BMS data logging and evaluating the occupants’ perception of a summer and a winter period indoor environment using a standardized questionnaire. In conclusion, indoor environmental quality in this historic building is unsatisfactory. Stuffy air, too high, too low and varying room temperatures, lighting problems and noise are constant issues. Although it is equipped with modern ventilation systems, there are still possibilities for improving thermal comfort by improved control strategies, since upgrading the building’s envelope is not allowed according to the Swedish Building Regulations in historic buildings with heritage value.

Acoustic Comfort Investigation in Residential Timber Buildings in Sweden

This article presents parts of a wide survey on acoustic comfort in Swedish family buildings, specificallywith focus on timber light-weight buildings. The scope of the whole research is to investigate acousticcomfort dimensions after collecting and combining data from standardized acoustic measurements andsubjective responses from a questionnaire survey. Certain noise sources were reported as dominantwithin living environments, impact noise from neighbors being the most important. Installation noisefrom inside the building and outdoor low-frequency noise disturb also a lot. However, the overall levelof acoustic comfort in contemporary wooden buildings seems satisfactory.

Lifecycle profit analysis of prefabricated multi-active façades

PurposeThe purpose of this paper is to identify appropriate concepts of multi-active façades for the renovation of multifamily buildings in Sweden and to determine which, if any, are financially viable.Design/methodology/approachA lifecycle profit (LCP) analysis was used to examine financial viability through a ten-step process, which included identifying concepts, assessing costs and prices, calculating the LCP and performing sensitivity analysis. Two existing buildings – one low rise and the other high rise – were used as reference models.FindingsThe findings were contradictory. Implementing any of the multi-active façade concepts on the high-rise building would be financially beneficial. The opposite was, however, the case for the low-rise building. Two factors causing this contradiction have been identified: the façade material before renovation and the size of the building.Research limitations/implicationsThe study is limited to two case buildings situated in Sweden; however, similar buildings represent a significant amount of the existing building stock. Part of the purpose of the study is also to investigate the merits of LCP analysis to evaluate energy-efficient retrofitting. The study implicates the benefits and pitfalls of LCP analysis needed to be considered by researchers and practitioners alike.Originality/valueThe research findings contribute to the understanding of energy-efficient retrofitting of existing multifamily buildings based on prefabricated multi-active façade concepts.

Building status obtained before renovating multifamily buildings in Sweden

The aim of this study was to analyse how energy use, building physics properties and indoor environment data have been obtained in the initial evaluation phases of multifamily building renovations in Sweden. Between 1964 and 1975, approximately one million homes were built in Sweden. These buildings are now in need of renovation. To perform proper status assessment of a building before a renovation is important both to make decisions on renovation measures on correct information as well as to be able to perform follow-ups of renovation projects. The analyses in this study was performed with questionnaires in eight case studies. Studied data included energy use, building physics properties and indoor environmental factors. The study shows that information about a building's status, and the subsequent renovation process, is often linked to one or just a few people involved in the project without any systematic documentation. When they leave their employment, due to changing jobs or retirement, documentation about the condition of the building, material choices and decision processes is often lost.

Final and primary energy use for heating new residential area with varied exploitation levels, building energy performance and district heat temperatures

Abstract There is great potential to build new energy-efficient building blocks in combination with efficient energy supply systems. Such a development will contribute to achieve national energy and climate goals as well as the overall aim for a sustainable development. Here, we analyze final and primary energy use for heating a new residential area by using district-heating. The area, located in Vaxjo, in south Sweden has potentially varied land exploitation levels, energy performance of buildings and district heat supply/return temperatures. The results show that the district heating demand will be reduced by about 52-56% if buildings in the area meet the Swedish passive house criteria instead of the Swedish building code. The exploitation levels of construction in the area strongly influence the total heating demands. A dense instead of a low exploitation will increase the area’s heating demand more than four times. But, the heat demand density of the residential area has quite a small impact on the total heat losses of the distribution network in contrast to changed supply and return temperatures. The distribution heat losses could be reduced by up to 50% with lower supply/return temperatures. However, a reduction of district heat supply/return temperatures to 50/20oC increases electricity use for boosting hot water temperature to avoid the risk of legionella bacteria. This causes a shift from district heat production to electricity production and increases the primary energy use. The results of this study can be used for further considerations of costs and benefits of energy supply options for new residential areas.

Cost-optimized energy-efficient building envelope measures for a multi-storey residential building in a cold climate

In this study we analyse cost-optimal building envelope measures including insulation for attic roof, ground floor and exterior walls, and efficient windows and doors for new buildings. The analysis is based on a multi-storey building in south of Sweden with an expected lifetime of at least 100 years. We integrate dynamic energy simulation, total and marginal economic analysis, and consider different scenarios of real discount rates and annual energy price increases. Our analysis shows that cost-optimal thicknesses of insulations for the building envelope elements are significantly higher than those required to meet the current Swedish building code’s minimum energy requirements. For windows, the cost-optimal U-value is about the same as required to fulfil the minimum requirement of the Swedish building code. Overall, large energy and cost savings are achieved when the cost-optimal measures are cumulatively implemented. Compared to the reference, annual space heating reduction of 28-43% is achieved for the building with the cost-optimal measures under the analysed period of 50 years. The cost savings varied between 21 and 188 k€.

Effects of end-of-life management options for materials on primary energy and greenhouse gas balances of building systems

In this study we have analysed the life cycle primary energy and greenhouse gas (GHG) balances of concrete-frame and timber-frame multi-storey building alternatives, designed to meet the current Swedish building code, considering different end-of-life scenarios. The scenarios include recycling of concrete and steel, cascading by recycling of wood into particle board and energy recovery at the end-of-life of the board, energy recovery of wood by combustion, and landfilling of wood with and without landfill gas (LFG) recovery. The energy recovered is assumed to replace fossil coal or gas. Our analysis accounts for energy and GHG flows in the production and end-of-life phases. We estimate the GHG emission changes achieved per unit of difference in finished wood in buildings or in harvest forest biomass between the timber buildings and the concrete building. The results show that the timber building systems give significantly lower life cycle primary energy balances than the concrete building system for all the end-of-life options. The concrete building system gives higher life cycle GHG balances than the timber alternatives for all the end-of-life options, except when wood is landfill without LFG recovery. The end-of-life primary energy and GHG benefit of wood materials is most significant for energy recovery while the benefit of cascading is low. However, replacing fossil gas instead of fossil coal significantly reduce the carbon benefits of the timber alternatives. The benefits of recycling steel and concrete are small. This study shows that end-of-life options for building materials can offer opportunities to reduce energy use and GHG emissions in the built environment.

Effect of different frame materials on the primary energy use of a multi storey residential building in a life cycle perspective

Primary energy implications over the life cycle of a multi storey residential building with different building systems are explored here. The main structural materials of the buildings include precast concrete, cross laminated timber (CLT) and prefabricated timber modules (modular). The analysis covers energy and material flows from different life cycle phases of the building versions, designed to meet the energy performance of the Swedish building code (BBR) and passive house criteria. The CLT and modular buildings were found to result in lower production primary energy use and higher biomass residues compared to the concrete alternative. The heating value of the recoverable biomass residues from the production phase of the CLT building is significantly larger than the primary energy required for its production. Primary energy use for production and construction constitutes 20–30% and 36–47% of the total primary energy use for production, construction, space heating, ventilation and demolition for the BBR and passive buildings, respectively. Space heating with combined heat and power (CHP) and ventilation electricity for the BBR and passive building versions form 70–79% and 52–63%, respectively, of the total primary energy use for production, construction, space heating, ventilation and demolition for a lifespan of 80 years. The CLT and modular buildings give 20–37% and 9–17% lower total life cycle primary energy use, respectively, than the concrete alternative when space heating is from CHP.

Relative Humidity, RH (%), a Problem or Not in Swedish Buildings

In 1972, the oil producing countries implemented an oil embargo on a number of states, including Sweden. During this period, oil was an important raw material for Sweden. The oil accounted for nearly 40% of Sweden’s total energy supply and was an extremely important source of heating for the Swedish building stock. Subsequently, restrictions from Swedish authorities have been introduced into how energy can be used. The purpose of these restrictions is to reduce energy consumption and a part of this is that new requirements have been introduced on how buildings should be designed. The changes have had negative consequences as people, who live in these types of buildings, claim that they suffer from health problems, which are referred to as “building related illness”. The purpose of this project is to examine how the structural changes regarding air exchange and windows carried out after the oil embargo in 1972, have affected the climate and environment in Swedish buildings. The aim is to investigate whether there are links between these changes and assertions about building-related illness. From an energy point of view, windows are a delicate building component and the project includes studying the effect of using an external roller shutter. Furthermore, the project aims to investigate how the environment and climate in Swedish buildings are experienced at the user level and how authorities assess the scope and effect of the measures they have implemented. The results show that unhealthily low levels of the relative humidity generally prevail in the Swedish housing stock and that the changes in the construction carried out after the oil embargo in 1972, regarding air exchange systems and window designs, reinforce the problem. With regard to various design alternatives, it is necessary in Sweden to consider the prevailing climate and environmental conditions and that the energy efficiency of the buildings is good.

Parametric multi-objective energy and cost analysis in the life cycle of nearly zero energy buildings − an exhaustive search approach

Possible cost saving potentials in planning and construction of high performing nearly zero energy buildings (nZEBs) with advanced energy standards are often not sufficiently assessed, as only a few, out of numerous possible variants of technology sets are considered in the traditional planning process. Often planning and analysis are not carried out in parallel, and the alternative technical options are discarded at an early stage. If, on the other hand, possible variants are realistically compared in the planning phase, a profound decision can be made. nZEB-design is also a multi-objective optimization problem where stakeholder interests' conflict with each other. This research addresses a methodological approach to better understand the effects that technical variables have on energy, environmental and economic performance over the whole life cycle of a multi-family residential building in Sweden. The research goal is to identify the most significant technical nZEB design variables organized into a consistent framework. In this paper, in a first step an exhaustive search method is assessed for a multi-family residential building in Sweden that systematically investigates all possible variant combinations. In a second step the derived results are applied to multiple objectives and optimisation goals for a multi-target decision-making framework so that different actors can decide between optimal solutions for different objectives. This approach seeks to explore a set of optimal solutions rather than to find a single optimal solution. On the one hand, a variety of technologies, such as insulation of the building envelope, ventilation or electricity and heat supply, and on the other hand a variation of the boundary conditions (such as observation period, user behaviour, energy price increases or CO2 costs) was investigated. The results were analysed energetically and economically over the life cycle of the building with the objectives of identifying coherences, deriving trends and optimizations over a time span of 40 years. The results show that the variance in the financing costs (20%) and the net present value (15%) is relatively low, whereas the primary energy demand (66%) and the CO2 (73%) emission vary in a broader range. The optimum cost curve in relation to CO2 emissions is very flat. Low emissions and energy requirements can, therefore, be achieved with different energy concepts as long as the envelope is very efficient. Due to the nature of an exhaustive search approach, it is also possible to find technical solution sets and design strategies with nearly equal financing cost and/or net present values, but with less primary energy consumption and/or CO2 emissions.