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  • 1.
    Allard, Ingrid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Hassan, Osama
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Energy evaluation methods for  residential buildings in Nordic countries2012In: Proceeding of the Technoport Conference, Elsevier, 2012Conference paper (Refereed)
    Abstract [en]

    To meet the goals of the directive 2010/31/EU on the energy performance of buildings, the building sector in Europe now faces a transition towards more energy efficient buildings. Research and development of new energy solutions and technology will be necessary for the transition and the importance of measuring and evaluating building energy performance increases. This paper attempts to review and evaluate different methods that are commonly used to analyze energy performance in residential buildings in Nordic countries, primarily in Sweden, Norway and Finland. A short international review of regulations is also included. Some advantages and disadvantages of each method are discussed, as well as commonly used methods in the three countries. Although the three Nordic countries have similar climate conditions and building traditions, the study shows that there exist relatively large variations in defining parameters related to energy performance in residential buildings, such as energy use, heated area, and climate zones. The outcome of the regulations could be investigated by adapting the codes on a selected set of buildings. Common analyzing methods, or parts of methods, are found to be used in several countries. These aspects may be considered in further work to develop more accurate and easily comparable methods to evaluate energy performance for residential buildings in cold climate.

  • 2.
    Allard, Ingrid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Hassan, Osama
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Methods for air tightness analysis for residential buildings in Nordic countries2012In: Methods for air tightness analysis forresidential buildings in Nordic countries, Southampton: WIT Press, 2012, p. 311-322Conference paper (Refereed)
    Abstract [en]

    Envelope air tightness is one factor that has impact on the energy performance ofbuildings. The goals of the directive 2010/31/EU, on energy performance ofbuildings, raise the importance of building energy performance analysis in theprocess. Measurements of air tightness can be useful both when evaluatingbuilding energy performance and developing new building techniques. The aimof this paper is to review and evaluate methods to measure air tightness in bothnew and existing residential buildings in Sweden, Norway and Finland, based onan international literature study and a survey. The methods are categorized basedon a number of criteria to determine their suitability in different situations.Advantages and disadvantages of the methods are discussed, as well ascommonly used methods in the three countries. The review shows that thestandard ISO 9972 is used for verification in all three countries, but alternativesexist that might be more suitable in certain situations. Simpler methods are usedin the building process to increase air tightness. To achieve a comparablemeasurement, both common methods and commonly defined units are needed.

  • 3.
    Allard, Ingrid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Hassan, Osama A. B.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Methods for energy analysis of residential buildings in Nordic countries2013In: Renewable & sustainable energy reviews, ISSN 1364-0321, E-ISSN 1879-0690, Vol. 22, p. 306-318Article, review/survey (Refereed)
    Abstract [en]

    To meet the goals of the directive 2010/31/EU on the energy performance of buildings, the building sector in Europe now faces a transition towards more energy efficient buildings. Research and development of new energy solutions and technology will be necessary for the transition and the importance of analyzing building energy performance increases. This paper aims to review and evaluate different methods that are commonly used to analyze energy performance in residential buildings in Nordic countries, primarily in Sweden, Norway and Finland. A short international review of regulations is also included. The goal is to find commonly used methods and possibilities for the future. The introduced methods are summarized, categorized and compared based on their advantages and disadvantages. Although the three Nordic countries have similar climate conditions and building traditions, the review shows relatively large variations in the definitions of energy performance for residential buildings, as well as variations in how measurements and calculations are used in the methods for energy performance analysis. In the conducted review, methods, or parts of methods, are also found to be used. The methods used to analyze energy performance are found to be more similar than the concepts of energy performance itself in the three countries. These aspects may be considered in further work to develop an international policy practice for energy performance of residential buildings in cold climate.

  • 4.
    Allard, Ingrid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nair, Gireesh
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Energy evaluation of residential buildings: Performance gap analysis incorporating uncertainties in the evaluation methods2018In: Building Simulation, ISSN 1996-3599, E-ISSN 1996-8744, Vol. 11, no 4, p. 725-737Article in journal (Refereed)
    Abstract [en]

    Calculation and measurement-based energy performance evaluations of the same building often provide different results. This difference is referred as "the performance gap". However, a large performance gap may not necessarily mean that there are flaws in the building or deviations from the intended design. The causes for the performance gap can be analysed by calibrating the simulation model to measured data. In this paper, an approach is introduced for verifying compliance with energy performance criteria of residential buildings. The approach is based on a performance gap analysis that takes the uncertainties in the energy evaluation methods into consideration. The scope is to verify building energy performance through simulation and analysis of measured data, identifying any performance gap due to deviations from the intended design or flaws in the finished building based on performance gap analysis. In the approach, a simulation model is calibrated to match the heat loss coefficient of the building envelope [kWh/K] instead of the measured energy. The introduced approach is illustrated using a single-family residential building. The heat loss coefficient was found useful towards identifying any deviations from the intended design or flaws in the finished building. The case study indicated that the method uncertainty was important to consider in the performance gap analysis and that the proposed approach is applicable even when the performance gap appears to be non-existing.

  • 5.
    Allard, Ingrid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nair, Gireesh
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Energy performance indicators in the Swedish building procurement process2017In: Sustainability, ISSN 2071-1050, E-ISSN 2071-1050, Vol. 9, no 10, article id 1877Article in journal (Refereed)
    Abstract [en]

    In Sweden, all new buildings need to comply with the National Board of Housing, Building and Planning’s requirement on specific purchased energy (kWh/m2). Accordingly, this indicator is often used to set design criteria in the building procurement process. However, when energy use is measured in finished buildings, the measurements often deviate significantly from the design calculations. The measured specific purchased energy does not necessarily reflect the responsibility of the building contractor, as it is influenced by the building operation, user behavior and climate. Therefore, Swedish building practitioners may prefer other indicators for setting design criteria in the building procurement process. The aim of this study was twofold: (i) to understand the Swedish building practitioners’ perspectives and opinions on seven building energy performance indicators (envelope air leakage, U-values for different building parts, average U-value, specific heat loss, heat loss coefficient, specific net energy, and specific purchased energy); and (ii) to understand the consequences for the energy performance of multi-family buildings of using the studied indicators to set criteria in the procurement process. The study involved a Delphi approach and simulations of a multi-family case study building. The studied indicators were discussed in terms of how they may meet the needs of the building practitioners when used to set building energy performance criteria in the procurement process.

  • 6.
    Allard, Ingrid
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Östin, Ronny
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    A methodology to investigate the building energy performance gap2015In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118Article in journal (Other academic)
    Abstract [en]

    In order to evaluate compliance with requirements on building energy performance, it is necessary to find strategies to process discrepancies from the results of forward simulations in the design stage and of measurements in the operated stage. The gap between designed performance and measured performance is referred to as the “performance gap”. It can be divided into a procurement gap (between intended design and verified performance) and an operational gap (between verified performance and non-normalized measurements).  

    In this work we introduced a methodology for performance gap analysis, based on separating the procurement- and operational gap. An important component to do this is calibrations of calculations using measured data. The suggested methodology allows for more detailed verifications of building energy performance and can be used to study how indicators reflect the performance gap. The proposed methodology is tested using data from a well-documented and measured operated single family building, in sub-arctic climate in Sweden.

    The indicators studied in the verification were carefully analyzed. The methodology was found reliable based on the obtained results and a sensitivity analysis. An overall observation is that the applicability of the methodology depends on the accuracy of the hybrid method. The accuracy of the performance gap analysis per definition depends on the available information of the operated building, and consequently to access to extensive measured data.

  • 7.
    Andersson, Staffan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Östin, Ronny
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Predictions of energy demand in buildings using neural network techniques on performance data1996In: Proceedings of the 4th fourth symposium on building physics in the nordic countries, 1996, p. 51-58Conference paper (Refereed)
  • 8.
    Andersson, Staffan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Sjögren, Jan-Ulric
    Östin, Ronny
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Building performance based on measured data2011In: World Renewable Energy Congress – Sweden, 8–13 May, 2011, Linköping, Sweden: Energy End-Use Efficiency Issues / [ed] Moshfegh, Bahram, Linköping: Linköping University Electronic Press , 2011, p. 899-906Conference paper (Refereed)
    Abstract [en]

    With increasing liability for builders, the need for evaluation methods that focuses on the building’s performance and thus excludes the impact from residents’ behavior increases. This is not only of interest for new buildings but also when retrofitting existing buildings in order to reduce energy end-use.

    The investigation in this paper is based on extensive measurements on two fairly representative type of buildings, a single family building in Ekerö, Stockholm built 2000 and two apartment buildings in Umeå (1964) in order to extract key energy performance parameters such as the building’s heat loss coefficient, heat transfer via the ground and heat gained from the sun and used electricity.

    With access to pre-processed daily data from a 2-month periods, located close to the winter solstice, a robust estimate of the heat loss coefficient was obtained based on a regression analysis. For the single family building the variation was within 1% and for the two heavier apartment buildings an average variation of 2%, with a maximum of 4%, between different analyzed periods close to the winter solstice.

    The gained heating from the used electricity in terms of a gain factor could not be unambiguously extracted and therefore could only a range for the heat transfer via ground be estimated. The estimated range for the transfer via ground for the two apartment buildings were in very good agreement with those calculated according to EN ISO 13 370 and corresponded to almost 10% of the heating demand at the design temperature. For the single family building with an insulated slab and parts of the walls below ground level, the calculations gave slightly higher transfer than what was obtained from the regression analysis. For the estimated gained solar radiation no comparison has been possible to make, but the estimated gain exhibited an expected correlation with the global solar radiation data that was available for the two apartment buildings.

  • 9.
    Andersson, Staffan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Sjögren, Jan-Ulric
    Östin, Ronny
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Prestanda- och betendeuppföljning av byggnaders energianvändning: etapp12010Report (Other academic)
  • 10.
    Azizi, Shoaib
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nair, Gireesh
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Comparative Study of Influential Factors on Implementation of Energy Efficiency Measures in Single-Family Houses in Cold Climate2018Conference paper (Refereed)
    Abstract [en]

    A combination of factors, which include occupants and building related aspects, could motivate homeowners to implement energy renovation (ER). This study applies a comparative approach to assess perspectives of single-family homeowners towards different energy efficiency measures (EEMs). The aim is to unveil the factors that are effective on the residents’ attitude and decision making to implement an EEM or a set of EEMs. The analysis is based on a questionnaire survey conducted during spring 2017 among1550 owners of single-family houses in seven municipalities in northern Sweden. Approximately, 35% of respondents expressed their interest to install energy efficient household appliances and solar photovoltaic (PV) systems. The analysis suggests significant relations between the homeowners’ interest to implement thermal envelope measures and the quality of the house such as age and indoor environmental problems such as cold surfaces. The group of respondents, who reported their heating cost to be high, are more likely to be interested in implementing thermal envelope measures than other measures such as HVAC. Several socio-economic factors are found to be significantly related with homeowners’ interest to implement EEMs.

  • 11.
    Brembilla, Christian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Lacoursiere, Claude
    Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
    Soleimani-Mohseni, Mohsen
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Investigation of thermal parameters addressed to a building simulation model2015In: Energy, Science and Technology 2015: Book of Abstracts. The energy conference for scientists and researchers / [ed] Karlsruher Institute of Technology (KIT), Karlsruher, Germany: Karlsruher Institute of Technology (KIT) , 2015, Vol. 1, p. 128-Conference paper (Refereed)
    Abstract [en]

    Introduction The uncertainty of setting input parameters in a building model can have a major impact on the simulated output. The tolerance of thermal parameters is a necessary information that helps modeler to know the influence of eachfactors on the outcomes. This paper shows the allowable tolerance of thermal parameters in order to build anaccurate building model.

  • 12.
    Brembilla, Christian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Lacoursiere, Claude
    Umeå University, Faculty of Science and Technology, High Performance Computing Center North (HPC2N).
    Soleimani-Mohseni, Mohsen
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Investigations of thermal parameters addressed to a building simulation model2015In: Proceedings of BS2015, India, Hyderabad: International Building Performance Simulation Association (IBPSA), 2015, , p. 2741-2748p. 2741-2748Conference paper (Refereed)
    Abstract [en]

    This paper shows the tolerance of thermal parameters addressed to a building simulation model in relation to the local control of the HVAC system. This work is suitable for a modeler that has to set up a building simulation model. The modeler has to know which parameter needs to be considered carefully and vice-versa which does not need deep investigations. Local differential sensitivity analysis of thermal parameters generates the uncertainty bands for the indoor air. The latter operation is repeated with P, PI and PID local control of the heating system. In conclusion, the local control of a room has a deterministic impact on the tolerance of thermal parameters.

  • 13.
    Brembilla, Christian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    One dimensional model of transient heat conduction through multilayer walls/slabs: The functionality of insulation and brick materials in terms of decrement factor and time lag2016Manuscript (preprint) (Other academic)
    Abstract [en]

    Multilayer wall is a common type of building envelope used in buildings located in cold climates. The building envelope is typically composed by internal and external masses made by bricks or concrete separated by a large thickness of insulation material. This paper investigates the thermal behavior of a multilayer wall subjected to temperature excitation on both wall sides. The analysis is conducted by discretizing the continuous space and time variables of the mathematical model identified in the heat equation. Euler backwards solves the numerical model of multilayer wall by providing an unconditionally stable solution. The step response test shows the correct working of the model which reaches the steady state solution. The results of this paper are expressed in terms of temperature of each wall layer against the time. In particular, (i) the large thickness of insulation material separates thermodynamically the outside external mass from the internal mass, (ii) 20 cm thickness of insulation material damps the heat wave with a decrement factor of 3.41 °ͦC and a time lag of 1 hour, (iii) the external brick layer damps the heat wave with a decrement factor of 1.97 °ͦC and a time lag of 5 hours.

  • 14.
    Brembilla, Christian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Renman, Ronny
    Östin, Ronny
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Soleimani-Mohseni, Mohsen
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    The impact of control strategies on space heating system efficiency in low-energy buildings2018Manuscript (preprint) (Other academic)
    Abstract [en]

    In this study efficiency factors measures the thermal energy performance for space heating. This study deals with the influence of control strategies on the effriciency factors of space heating and its distribution system. An adaptive control is developed and applied to two types of heating curves (linear and non-linear) for a low-energy building equipped with renewable energy sources. The building is modelled with a hybrid approach (law driven + data driven model). The design of the floor heating is calibrated and validated by assessing the uncertainty bands for low temperatures and mass flow rate. advantages and disavantages of linear and non-linear heating curves are highlighted to illustrate their impact on space heating thermodynamic behaviour and on the efficiency factors of the space heating system.

    Practical application: The study reveals that applying commercial building energy simulation software  is worthwhile to determine reliable performance predictions. Oversimplified building models, in particular when considering building thermal mass, are not capable of simulating the thermodynamic response of a building subjected to different control strategies. The application of different heating cuirves (linear and non-linear) to massless building models leaves the amount of mass flow rate delivered to the space heating unchanged when the building is subjected to sharp variations of the outdoor temperature.

  • 15.
    Brembilla, Christian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Soleimani-Mohseni, Mohsen
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Hybrid heating system for open-space office/laboratory2015In: Energy, Science and Technology 2015: Book of Abstracts. The energy conference for scientists and researchers / [ed] Karlsruher Institut für Technologie (KIT), Karlsruher, Germany: Karlsruhe, KIT , 2015, Vol. 1, p. 315-315Conference paper (Refereed)
    Abstract [en]

    Open-space office/laboratory are quite common in Scandinavia and they are usually designed for multipurposework. There are office area where is possible to work standing up and in the same time to work at the desk. Forthis purpose a hybrid heating system made by electric convectors and panel radiators is investigated. Two stepresponse tests of the hybrid heating system are performed at the laboratory of Umeå University. The first test isexecuted during the week, disturbances from heat sources degrading the quality of the results. The second test isperformed during week-end. The error analysis shows a maximum discrepancies of +0.6 °C between measuredand simulated data. However, a thermal time constant of the room can be deducted and use it for controlling purposes.

  • 16.
    Brembilla, Christian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Soleimani-Mohseni, Mohsen
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Transient model of a panel radiator2015In: Energy, Science and Technology 2015: Book of Abstracts. The energy conference for scientists and researchers / [ed] Karlsruher Institut für Technologie (KIT), Karlsruher, Germany: Karlsruher Institut für Technologie (KIT) , 2015, Vol. 1, p. 321-321Conference paper (Refereed)
    Abstract [en]

    This paper shows a detailed transient model of a panel radiator considered as a system of multiple storageelements. The experiment records the temperature surface of the panel in the process of heating up. Thequalitative results of the experiment suggest the more appropriate technique for modelling this technology. The transient model performs the modelling with horizontal thermal capacitances connected in series. This modelcalculates the temperature of exhaust flow, heat emission towards indoor environment, temperature gradient onpanel surface, dead and balancing time identified numerically on the chart.

  • 17.
    Brembilla, Christian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Soleimani-Mohseni, Mohsen
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Transient model of a panel radiator2015In: Proceedings of BS2015: 14th Conference of International Building Performance Simulation Association, Hyderabad, India, Dec. 7-9, 2015, India, Hyderabad: International Building Performance Simulation Association (IBPSA), 2015, , p. 2749-2756p. 2749-2756Conference paper (Refereed)
    Abstract [en]

    This paper shows a transient model of a hydronic panel radiator modelled as a system of multiple storage elements. The experiment´s results suggest the more suitable technique for modelling this technology. The panel radiator is modelled numerically with eight thermal capacitance connected in series by keeping a memory of the heat injected in the thermal unit. The comparison of the performance among lumped steadystate models and transient model, in terms of heat emission and temperature of exhaust flow, shows the potential of the latter approach. To conclude, (1) the transient phase is essential for modelling stocky panels, and (2) this type of modelling has to be addressed for evaluating the performance of low energy buildings.

  • 18.
    Brembilla, Christian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Vuolle, Mika
    EQUA simualtion.
    Östin, Ronny
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Practical support for evaluating efficiency factors of a space heating system in cold climates: modelling and simulation of hydronic panel radiator with different location of connection pipes2017In: Energy Efficiency, ISSN 1570-646X, E-ISSN 1570-6478, Vol. 10, no 5, p. 1253-1267Article in journal (Refereed)
    Abstract [en]

    Plenty of technical norms, included in the EPBD umbrella, assess the performance of buildings or its sub-systems in terms of efficiency. In particular, EN 15316 and its sub-sections, determine the system energy requirements and the system efficiencies of space heating system. This paper focuses on the estimation of efficiencies for emission of hydronic radiators. The assessment of efficiencies for emission occurs by evaluating the amount of heat emitted  from the heat emitter and the extra thermal losses towards building envelope. The heat emitted from radiators varies during the heating up/cooling down phases. A factor that influences the heat emitted during these phases is the location of connection pipes of the radiator. Connection pipes can be located on opposite side or at the same side of the radiator. To better estimate the heat emitted from radiators a transient model with multiple storage elements is used in a building simulation model. Sensitivity analysis encompasses all  the possible variations on extra thermal losses due to the building location in different climates, the heaviness of active thermal mass and the type of radiator local control. The final outcome of this paper is a practical support where the designer can easily assess the efficiencies for emission of hydronic radiators  for Swedish buildings. As main result, (i) the efficiency for control of space heating system is higher in Northern climates than in Southern climates, (ii) heavy active thermal masses allow higher efficiencies for emission than light active thermal masses, (iii) connection pipes located on the same side of the radiator enable higher efficiencies for emission than pipes located on opposite side.

  • 19.
    Brembilla, Christian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Östin, Ronny
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Predictions' robustness of one-dimensional model of hydronic floor heating: novel validation methodology using a thermostatic booth simulator and uncertainty analysis2018In: Journal of Building Physics, ISSN 1744-2591, E-ISSN 1744-2583, Vol. 41, no 5, p. 418-444Article in journal (Refereed)
    Abstract [en]

    Hydronic floor heating models provide predictions in estimating heat transfer rates and floor surface temperature. Information on the model performance and range of validity of its results are often lacking in literature. Researchers have to know the accuracy and robustness of the model outcomes for performing energy and climate comfort calculations. This article proposes a novel validation methodology based on the uncertainty analysis of input data/parameters of one-dimensional model of hydronic floor heating tested in a thermostatic booth simulator and compared with experimental measurements. The main results are: (1) prediction accuracy between 0.4% and 2.9% for Tf and between 0.7% and 7.8% for qup when the serpentine has tube spacing (p) of 0.30 m, (2) prediction accuracy between 0.5% and 1.4% for Tf and between 8.7% and 12.9% for qup with p = 0.15m and (3) Tfld mostly affects predictions with oscillations between 6.2% and 2.2% for qup. This model provides robust and reliable predictions exclusively for qup when p = 0.30m.

  • 20.
    Brembilla, Christian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Östin, Ronny
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Soleimani-Mohseni, Mohsen
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Paradoxes in understanding the Efficiency Factors of Space Heating2018In: Energy Efficiency, ISSN 1570-646X, E-ISSN 1570-6478Article in journal (Refereed)
    Abstract [en]

    Efficiency factors are here defined as the thermal energy performance indicators of the space heating. Until recently, the efficiency factors were assumed as one value for space heating located inany climate. This study addresses the problem of how the outdoor climate affects the efficiency factors of a space heating equipped with 1D model of hydronic floor heating. The findings show how the efficiency factors, computed with two numerical methods, are correlated with the solar radiation. This study highlights the paradoxes in understanding the results of efficiency factors analysis. This work suggests how to interpret and use the efficiency factors as a benchmark performance indicator.

  • 21. Bränberg, Agneta
    et al.
    Holmgren, Ulf
    Chrsitensen, Bendt
    Eklund, Robert
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Ramstedt, Madeleine
    Undervisningens forskningsanknytning2014Conference paper (Refereed)
  • 22.
    Cheng, Xiaogang
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. College of Telecommunications and Information Engineering, Nanjing University of Posts and Telecommunications, Nanjing, China; School of Electrical Engineering and Computer Science, Royal Institute of Technology, Stockholm, Sweden.
    Yang, Bin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. School of Environmental and Municipal Engineering, Xi’an University of Architecture and Technology, Xi'an, China.
    Liu, Guoqing
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    A total bounded variation approach to low visibility estimation on expressways2018In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 18, no 2, article id 392Article in journal (Refereed)
    Abstract [en]

    Low visibility on expressways caused by heavy fog and haze is a main reason for traffic accidents. Real-time estimation of atmospheric visibility is an effective way to reduce traffic accident rates. With the development of computer technology, estimating atmospheric visibility via computer vision becomes a research focus. However, the estimation accuracy should be enhanced since fog and haze are complex and time-varying. In this paper, a total bounded variation (TBV) approach to estimate low visibility (less than 300 m) is introduced. Surveillance images of fog and haze are processed as blurred images (pseudo-blurred images), while the surveillance images at selected road points on sunny days are handled as clear images, when considering fog and haze as noise superimposed on the clear images. By combining image spectrum and TBV, the features of foggy and hazy images can be extracted. The extraction results are compared with features of images on sunny days. Firstly, the low visibility surveillance images can be filtered out according to spectrum features of foggy and hazy images. For foggy and hazy images with visibility less than 300 m, the high-frequency coefficient ratio of Fourier (discrete cosine) transform is less than 20%, while the low-frequency coefficient ratio is between 100% and 120%. Secondly, the relationship between TBV and real visibility is established based on machine learning and piecewise stationary time series analysis. The established piecewise function can be used for visibility estimation. Finally, the visibility estimation approach proposed is validated based on real surveillance video data. The validation results are compared with the results of image contrast model. Besides, the big video data are collected from the Tongqi expressway, Jiangsu, China. A total of 1,782,000 frames were used and the relative errors of the approach proposed are less than 10%.

  • 23.
    Cheng, Xiaogang
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. Nanjing Univ Posts & Telecommun, Coll Telecommun & Informat Engn, Nanjing, Jiangsu, Peoples R China; Royal Inst Technol, Sch Comp Sci & Commun, Stockholm, Sweden.
    Yang, Bin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Liu, Guoqing
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Li, Haibo
    A variational approach to atmospheric visibility estimation in the weather of fog and haze2018In: Sustainable cities and society, ISSN 2210-6707, Vol. 39, p. 215-224Article in journal (Refereed)
    Abstract [en]

    Real-time atmospheric visibility estimation in foggy and hazy weather plays a crucial role in ensuring traffic safety. Overcoming the inherent drawbacks with traditional optical estimation methods, like limited sampling volume and high cost, vision-based approaches have received much more attention in recent research on atmospheric visibility estimation. Based on the classical Koschmieder's formula, atmospheric visibility estimation is carried out by extracting an inherent extinction coefficient. In this paper we present a variational framework to handle the nature of time-varying extinction coefficient and develop a novel algorithm of extracting the extinction coefficient through a piecewise functional fitting of observed luminance curves. The developed algorithm is validated and evaluated with a big database of road traffic video from Tongqi expressway (in China). The test results are very encouraging and show that the proposed algorithm could achieve an estimation error rate of 10%. More significantly, it is the first time that the effectiveness of Koschmieder's formula in atmospheric visibility estimation was validated with a big dataset, which contains more than two million luminance curves extracted from real-world traffic video surveillance data.

  • 24.
    Cheng, Xiaogang
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. College of Telecommunications and Information Engineering, Nanjing University of Posts and Telecommunications, Nanjing, China.
    Yang, Bin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Liu, Guoqing
    Li, Haibo
    A pilot study of online non-invasive measuring technology based on video magnification to determine skin temperature2017In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 121, p. 1-10Article in journal (Refereed)
    Abstract [en]

    Much attention was paid on human centered design strategies for environmental control systems of indoor built environments. The goal is to achieve thermally comfortable, healthy and safe working or living environments in energy efficient manners. Normally building Heating, Ventilation and Air Conditioning (HVAC) systems have fixed operating settings, which can't satisfy human thermal comfort requirements under transient and non-uniform indoor thermal environments. Therefore, human thermal physiology signal such as skin temperature, which can reflect human body thermal sensation, has to be measured over time. Several trials have been performed by minimizing measuring sensors such as i-Button and mounting measuring sensors into wearable devices such as glasses. Infrared thermography technology has also been tried to achieve non-invasive measurements. However, it would be much more convenient and feasible if normal computer camera could record images, which could be used to obtain human thermal physiology signals. In this study, skin temperature of hand back, which has a high density of blood vessels and is normally not covered by clothing, was measured by i-button sensors. Images recorded by normal camera were amplified to analyzing skin temperature variation, which are impossible to see with naked eyes. The agreement between i-button sensor measuring results and image magnification results demonstrated the possibility of non-invasive measuring technology by image magnification. Partly personalized saturation-temperature model (T = 96.5 × S + bi) can be used to predict skin temperatures for young East Asia females.

  • 25.
    Fischl, Geza
    et al.
    Umeå University, Faculty of Science and Technology, Umeå School of Architecture.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Design av terapeutiska miljöer2012In: Byggnadsrelaterad ohälsa i Kvarkenregionen: nio delprojekt om miljökänslighet, luftkvalitet och sjuka hus ur ett tvärvetenskapligt perspektiv : slutrapport för projektet Kompetenscentrum Byggnad - Luftkvalitet - Hälsa 2 (KLUCK 2) / [ed] Martina Österberg, Vasa: Yrkeshögskolan Novia , 2012, p. 103-110Chapter in book (Other academic)
    Abstract [sv]

    Terapeutiska miljöer kan ha en kraftfull, läkande effekt på patienter – de sänker stressnivån vilket gör att patienternas medicinska tillstånd förbättras. Entydiga forskningsresultat visar att t.ex. vistelse i naturen, motion, fysisk rörelse och förbättrade sociala aktiviteter gör att patienters återhämtningsförmåga stärks och stressnivån sjunker. De terapeutiska miljöerna ger en ökad känsla av kontroll, stärkt integritet och förbättrat social stöd. Genom att erbjuda positiv stimulans, såsom konst eller musik, förstärks den goda upplevelsen ytterligare. Trots att man i olika evidensbaserade forskningsstudier bevisat att terapeutiska miljöer har positiv inverkan på patienters hälsa och välbefinnande är dessa miljöer mindre kända hos allmänheten, som därför inte heller efterfrågar dem i samband med vård. Förmodligen är utbildning av allmänheten en framkomlig väg att för att höja medvetenheten om terapeutiska miljöers hälsofrämjande effekt.

  • 26. Glader, Annika
    et al.
    Östman, Leif
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Fuktskadade byggnader: kompetensutveckling inom byggbranschen2015Report (Other academic)
    Abstract [en]

    When solving problems with the indoor environment, the diversity of names of operators in the construction industry has caused problems for clients in the selection of qualified building investigators. The overlaps in education systems and the lack of qualification boundaries have caused problems also for educators and students. To meet the need for expertise in the field, one has so far been relying on voluntary, fee-based training courses. Still, this system has not been able to meet the need. A working group, within the moisture and mould programme in Finland, has developed a plan for the development of education and skills for those who work with investigations and renovations of moisture and mould damaged buildings. Most polytechnics with construction education have some form of training concerning the indoor environment and renovation, although the number of hours for classroom teaching varies greatly. Some schools have already sufficiently comprehensive training to meet some of the new proposals on skill requirements. Novia University of Applied Sciences is responsible for the education of construction engineers and builders in Swedish in Finland and have, within the project TEMA, started the development of Swedish training materials and strategies.

  • 27. Lidberg, T.
    et al.
    Olofsson, T.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics. School of Technology and Business Studies, Dalarna University, 791 88, Falun, Sweden.
    Trygg, L.
    System impact of energy efficient building refurbishment within a district heated region2016In: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 106, p. 45-53Article in journal (Refereed)
    Abstract [en]

    The energy efficiency of the European building stock needs to be increased in order to fulfill the climate goals of the European Union. To be able to evaluate the impact of energy efficient refurbishment in matters of greenhouse gas emissions, it is necessary to apply a system perspective where not only the building but also the surrounding energy system is taken into consideration. This study examines the impact that energy efficient refurbishment of multi-family buildings has on the district heating and the electricity production. It also investigates the impact on electricity utilization and emissions of greenhouse gases. The results from the simulation of four energy efficiency building refurbishment packages were used to evaluate the impact on the district heating system. The packages were chosen to show the difference between refurbishment actions that increase the use of electricity when lowering the heat demand, and actions that lower the heat demand without increasing the electricity use. The energy system cost optimization modeling tool MODEST (Model for Optimization of Dynamic Energy Systems with Time Dependent Components and Boundary Conditions) was used. When comparing two refurbishment packages with the same annual district heating use, this study shows that a package including changes in the building envelope decreases the greenhouse gas emissions more than a package including ventilation measures. 

  • 28. Lidberg, Tina
    et al.
    Ramirez, Ricardo
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Norrman Eriksson, Ola
    An approach to illustrate strategies to improve energy efficiency at a municipal level2014Conference paper (Refereed)
  • 29.
    Lindbergh, Lars
    et al.
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Business Administration.
    Jacobsson, Mattias
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Business Administration.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wilson, Timothy
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Business Administration.
    Public Housing in Sweden: The Umeå Two-Step2017In: NFF Proceedings: Bodö, 23-25 August 2017, 2017Conference paper (Other academic)
    Abstract [en]

    Comparative housing analyses often find that Swedish public housing represents an interesting story because it provides a good class of rental housing to all sections of the population. This approach has been called the “Swedish public housing model”. An in-depth case study has been used to develop a system-wide understanding of a participant’s involvement in its housing market. In this case study, the public utility/energy and water-sewage/solid waste companies played a significant role in the company’s ability to serve the local community. It thus behooves us to compare and connect the different components in the public housing company business model to complete the analysis of success in the value chain. Two-levels describe the situation. At the first level, the municipal public housing (MPH) organization is seen as functioning as a tenant-oriented, quasi-municipal utility within a value network composed of the municipality + the energy utility + the water-sewage/solid waste company. At the second level, a Shaffer analysis shows general harmony among the operations of each organization.  In particular, the MPH provides value-for-money rentals within the municipality and helps tenants turn their flats into homes. Additionally, continued appreciation of its base assets and apparent economies of scale were instrumental in the success of the operations at the tactical level. Insofar as the Swedish public housing model is undergoing a shift to be more “business-like”, this study indicates how the model successfully works at the individual company level. Because there are certain commonalities with other organizations in public management, observations may be relevant in their successful operations.

  • 30.
    Lindbergh, Lars
    et al.
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Business Administration.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Vesterberg, Jimmy
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Andersson, Staffan
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wilson, Timothy
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Business Administration.
    Reflections on sustainable Ålidhem: a case study in Swedish municipal public housing refurbishment2018In: Property Management, ISSN 0263-7472, E-ISSN 1758-731X, Vol. 36, no 2, p. 203-220Article in journal (Refereed)
    Abstract [en]

    Purpose: This work is initiated under the premise that reliable evaluation methods are necessary to ensure investments in energy conservation, and the purpose of this paper is to contribute to that literature. It describes some pilot changes and their impact in an actual field study oriented toward upgrading municipal public housing (MPH) units.

    Design/methodology/approach: The research for this paper was connected to an MPH refurbishment project situated in northern Sweden. The overall energy efficiency goal within the project was a 40-50 percent reduction in the supplied energy for central electricity, domestic hot water and space heating. In order to evaluate if these goals were feasible, a measurement system was installed in a pilot building and in a neighboring building used as a reference. The evaluation was conducted by comparing the post-retrofit performance of the pilot building with the performance of the reference building when it was kept in its initial state (a comparison possible because both buildings had initial similarities).

    Findings: Impacts could be quantified insofar as a reference (control) building in the same environment was sustained for comparison purposes. A 43 percent improvement was observed in energy utilization in the pilot building compared to its reference companion (99.8 vs 174.5 kWh/m2 per year). When the approach described herein was applied to new construction, the present goal of 65 kWh/m2 was approached as measured by Swedish standards.

    Practical implications: Results should be of interest to academics in the housing field, professionals involved in refurbishment and residents themselves, renting MPH flats.

    Originality/value: This study is unique in the following ways: first, it really was a field experiment with a control, thus it did not have any exogenous interference in interpreting results. To the best of our knowledge, this is the first study of its kind. The second interesting characteristic was that results were subsequently used in the refurbishment of other buildings in the complex and in the construction of others. The major value of the paper may be associated with its timing. It comes at a time when the Kyoto agreement has raised concerns about sustainability, but also at a time when many buildings are facing a need for refurbishment.

  • 31.
    Lindbergh, Lars
    et al.
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Business Administration.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Vesterberg, Jimmy
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Wilson, Timothy L.
    Umeå University, Faculty of Social Sciences, Umeå School of Business and Economics (USBE), Business Administration.
    Project Ålidhem: a case study of a sustainable Swedish municipal public housing installation2017In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 121, p. 11-17Article in journal (Refereed)
    Abstract [en]

    A refurbishment project conducted within a municipal public housing complex is described and discussed through Project Ålidhem in northern Sweden. The overall energy efficiency goal within the project was a 40-50% reduction in the supplied energy for domestic hot water, building electricity and space heating. In the pilot study, a 43% improvement was observed. This paper focuses on the performance of four buildings constructed under a Delegation for Sustainable Cities program that specified an energy efficiency goal of 65 kWh/m2. This goal was approached, but not attained. Observations of utilization in four free-standing buildings were 68.3, 76.8, 87.2 and 87.6 kWh/m2 per year respectively, which are described and discussed herein.

  • 32.
    Mahlia, T.M. Indra
    et al.
    University of Malaya.
    Ng, H.M.
    University of Malaya.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Andriyana, A.
    University of Malaya.
    Energy and cost savings of optimal thickness for selected insulation materials and air gaps for building walls in tropical climate2012In: Energy Education Science & Technology, Part A: Energy Science and Research, ISSN 1308-772X, Vol. 29, no 1, p. 649-662Article in journal (Refereed)
    Abstract [en]

    Air conditioning usage in buildings is one of the major energy consumption sources due to thermal comfort requirement in tropical climate. An efficient building thermal insulation can reduce the energy consumption for cooling systems due to heat transfer from ambient. Therefore, it is crucial to study the effectiveness of energy saving by thermal insulation for buildings. In this study, the savings of ten selected building thermal insulation materials on the energy consumption of air-conditioning for cooling are evaluated based on tropical climate condition in Malaysia. The life-cycle cost analysis is conducted is calculated based on the energy savings. The results have revealed that life cycle cost is varying from 73 to 85%/m2 wall and energy saving from 85 to 92%/m2wall, which can be achieved depending on the insulation material used at their optimal thickness. The insulations Stropor exhibit optimal results in terms of economic benefits. The energy savings of air gap in the wall construction is also investigated for the selected insulation material. It is found that additional 0.64%/m2w all of life cycle cost savings can be achieved by applying 6 cm air gap at the selected insulation at optimal thickness.

  • 33.
    Maria, Boman
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Golriz, Mohammad R
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    The Solar Contribution to the Energy Use for Heating of Residential Buildings2004In: Proceedings of the CIB World Building Congress, 2004Conference paper (Refereed)
    Abstract [en]

    The energy use of residential buildings in cold and mild climates with the influence of the solar gaincan be simulated with the support of TEKLA 2.0. The model is adjusted to single-zone buildings thathave a uniform internal temperature. The calculations are based on the standard EN 832, whichincorporates dated or undated references and provisions from other publications. The predicted resultscorrespond well with the measured data from a monitored occupied residential reference building InUmeå, Sweden.A parameter study was made with TEKLA 2.0 on simulated data of the reference building for climateconditions in Umeå, Kiruna and Lund, Sweden. It indicates that the parameters that have the mostinfluence on the thermal performance of the building according to the components are the U-value ofthe wall, the thickness of roof insulation and the U-value of windows. The parameters that have themost influence on the solar gain are the daily average global solar radiation and the directions of thewindows provided.

  • 34.
    Meier, Alan
    et al.
    Lawrence Berkeley National Laboratory, USA.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Lamberts, Roberto
    Federal University of Santa Catarina, Brazil.
    What is an energy efficient building2002In: ENTAC 2002 - IX Meeting of technology in the built environment, 2002, p. 3-12Conference paper (Refereed)
    Abstract [en]

    Proposed regulations in Brazil call for minimum energy efficiencies in building design and appliance manufacture. These regulations are expected to translate into lower operating costs for the occupants, reduced energy demand for the utilities, and potentially lower carbon emissions for the country. The concept of “energy efficient” buildings has immediate implications on regulations, economics, energy demand, and the environment. A definition is also needed to compare building energy performance or to assess absolute energy efficiency. We propose three criteria for an energy efficient building: 1) the building must be equipped with efficient equipment and materials appropriate for the location and conditions; 2) the building must provide amenities and services appropriate to the building’s intended use; and 3) the building must be operated in such a manner as to have a low energy use compared to other, similar buildings. An efficient building must, at a minimum, be above average in all three aspects. When setting minimum efficiency standards, a definition of energy efficiency based on minimum life cycle costs is likely to result in much stricter standards—and greater energy savings—than a strategy based on eliminating the least efficient units.

  • 35. Myhren, Jonn Are
    et al.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Bergdahl, Martin
    Lågtemperaturuppvärmning med tilluftsradiator och värmeåtervinning i frånluft: en varsam renovering av flerbostadshus för energieffektivisering2014Book (Other academic)
  • 36.
    Nair, Gireesh
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Allard, Ingrid
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Åstrand, Anders
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Building professionals' views on energy efficiency compliance requirements2017In: 11th Nordic Symposium on Building Physics, NSB 2017 / [ed] Geving S., Time B., Elsevier, 2017, Vol. 132, p. 988-993Conference paper (Refereed)
    Abstract [en]

    In Sweden, the national building code (BBR) stipulates the specific energy use as an indicator to verify whether a newbuilding is complying with its design-phase energy performance values. However, previous studies have shown that there may belarge differences between the calculated specific energy and the actual monitored energy use. The differences are attributed tovarious reasons including the actual energy behaviour of the occupants as compared to the standard values used in thesimulations. This may lead to disputes between the client and the contractor on the responsibility of meeting the energyrequirements.In this study an adapted version of Delphi methodology was used to understand the building professionals’ view on variousindicators used to verify building energy performance. The study showed that professionals are concerned with the use of specificenergy as an indicator in the building procurement process as they do not have control over the occupants’ energy behaviour.Majority of the professionals expressed a large confidence in the average U-value of the building, component U-values and thespecific heat loss figure by the Swedish center for zero-energy buildings as indicators of building energy performance.

  • 37.
    Nair, Gireesh
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Azizi, Shoaib
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    A management perspective on energy efficient renovations in Swedish multi-family buildings2017In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 132, p. 994-999Article in journal (Refereed)
    Abstract [en]

    Sweden has around 2.5 million dwellings in multi-family buildings, which constitute about 55% of the total dwelling units. The multi-family building ownership in Sweden can be categorized into municipal, private and co-operative ownership. Approximately 40% of apartments in multi-family buildings belong to municipal housing companies, while the rest is equally shared by private companies and co-operative housing associations. These organizations have different priorities, limitations and concerns related to energy renovations. Accordingly, in this sector the decisions to invest in energy efficiency improvement depends to a large extent on the type of ownership.

    In this study we analyzed the perspectives of different types of building ownership on energy efficient renovation. The analysis is based on detailed interviews of 4 senior managers representing the multi-family buildings under different ownership categories. Along with this we also interviewed a municipality energy adviser. All the interviewees are based in in North Sweden. The drivers to facilitate the rate of adoption of energy renovation in such buildings are discussed.

  • 38.
    Nair, Gireesh
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nordlund, Annika
    Umeå University, Faculty of Social Sciences, Department of Psychology. Umeå University, Faculty of Social Sciences, Department of Geography and Economic History, Economic and social geography, Transportation Research Unit (TRUM).
    Hudson, Christine
    Umeå University, Faculty of Social Sciences, Department of Political Science.
    Comparative evaluation of city dwellers’ perspectives on household energy use based on housing tenure: survey results from Northern Sweden2019In: Cold Climate HVAC 2018: Sustainable Buildings in Cold Climates / [ed] Johansson, Dennis, Bagge, Hans, Wahlström, Åsa, Switzerland: Springer Publishing Company, 2019, 1, p. 791-802Chapter in book (Refereed)
  • 39.
    Nordlund, Annika
    et al.
    Umeå University, Faculty of Social Sciences, Department of Psychology.
    Nair, Gireesh
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Hudson, Christine
    Umeå University, Faculty of Social Sciences, Department of Political Science.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Att utveckla en stadsdel på ett hållbart sätt: en fråga om energi, transporter och människor2018Report (Other academic)
  • 40.
    Nordwall, Ulf
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    A quantitative approach for valuating architectural qualities2011In: The Open Construction and Building Technology Journal, ISSN 1874-8368, Vol. 5, p. 105-112Article in journal (Refereed)
    Abstract [en]

    Architectural qualities is often valuated based on a describable nature with a more personal interpretation, such as living space, size of ground plot, the number of sanitation rooms, or standard points according to the property taxation. Models with values of a more measurable qualitative nature, such monetary parameters,are less used. Within other research areas, for example the environmental and economic field, there are examples of well used qualitative models. One example is the Contingent Valuation (CV) model. It can be used to measure values in terms of willingness to pay on a hypothetic market. In this paper we introduce adirect quantitative approach for evaluating architectural qualities based on the theory of CV. The architectural qualities investigated are: the patina and mellowness of building components, usage flexibility within the apartment, and properties and characteristics of the surroundings.

    The method has been applied on a smaller case-study of 150 people living in cooperative and rented flats at Ålidhem, Ålidbacken and Östermalm in Umeå, Sweden. The case study was used merely to demonstrate and evaluate the methodology. The study indicated that the introduced three architectural values could be investigated with the used CV approach. It was found that the tenants had a measureable willingness to pay for those qualities. This supports a notion that valuations of architectural qualities are not entirely subjective and dependent on the individuals. Consequently the study supports the proposal to use qualitative measures to grade and compare such qualities.

  • 41.
    Nordwall, Ulf
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Architectural caring. Architectural qualities from a residential property perspective2013In: Architectural Engineering and Design Management, ISSN 1745-2007, E-ISSN 1752-7589, Vol. 9, no 1, p. 1-21Article in journal (Refereed)
    Abstract [en]

    A common definition of architectural qualities in general and the values of the qualities in particular can differ significantly in the understanding of different operators in the building construction sector. One platform to define and investigate architectural qualities is to use a property management perspective and focus on the tenants and their individual well-being in the accommodation. In this study, architectural qualities were investigated in three residential areas with multi-family buildings in Sweden: Backa Röd, Högsbohöjd and Nybodahöjden. The data were collected from interviews with building industry people and the residential tenants. Three architectural qualities became the foundation for the interviews: properties and characteristics of the surroundings, usage flexibility within the apartment, the patina and mellowness of building components. The investigation of collected data was inspired by a method called grounded theory (GT). In this study, GT was used to discover and develop a theory of architectural caring, where architectural qualities have a bearing on the nature of a residential area. We found that a central focus in the residential property management perspective is architectural caring. To care for the houses, materials, construction and the neighbourhood environment is to care for the residents and give them a sense of belonging.

  • 42.
    Nordwall, Ulf
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Hållbara hus i kallt klimat / Sustainable buildings in a cold climate2018Book (Other academic)
    Abstract [sv]

    Boken beskriver hur hållbar arkitektur kan vara utformad i subarktiskt och arktiskt klimat. Detta visas genom 31 exempel på hållbart byggande i Finland, Sverige, Norge, Svalbard, Island, Grönland, Kanada och USA. Projekten presenteras ur sex hållbarhetsperspektiv - energi, material, återbruk, platsen, klimat och funktion. Varje hus presenteras med bilder och arkitektens beskrivning av huset.Varje projekt har även text på engelska.

  • 43.
    Nordwall, Ulf
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, ThomasUmeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Hållbara hus i kallt klimat: 22 hållbara hus från Bollnäs till Kiruna 1994–20142014Collection (editor) (Other academic)
  • 44.
    Nordwall, Ulf
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Sustainable architecture in northern subarctic and artic climate2018Conference paper (Refereed)
  • 45.
    Ohlsson, Anders K. E.
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Östin, Ronny
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Accurate and robust measurement of the external convective heat transfer coefficient based on error analysis2016In: Energy and Buildings, ISSN 0378-7788, E-ISSN 1872-6178, Vol. 117, p. 83-90Article in journal (Refereed)
    Abstract [en]

    Accurate measurement of the convective heat transfer coefficient hc at external surfaces, e.g. at building facades and roofs, is of fundamental importance for heat transfer studies of the built environment. There are two basic methods for measurement of hc, the Loveday and Ito methods, which use one and two heated sensor units, respectively. To guide in selection of method and operating conditions, and in design of the sensor, we performed an error analysis. This included estimation of systematic errors, comparison between methods, and to established Nusselt number correlations, sensitivity analysis, and an evaluation of the measurement uncertainty. The main conclusion was that both methods, at forced convection, yielded measurement uncertainties at the 4 % level, provided that the Ito method was operated under the new condition, where one of its sensors remained unheated. However, at natural convection conditions, the Ito method cannot be operated with one of its sensors unheated, since hc is then zero at that sensor surface, which violates the method assumption that hc is the same at both sensors. Sensitivity analysis showed that systematic errors will be reduced by decreasing the sensor surface emissivity. The major source of measurement uncertainty was the conductive heat flux estimate.

  • 46.
    Ohlsson, Anders
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Yang, Bin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Ekblad, Alf
    Örebro universitet.
    Boman, Christoffer
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Nyström, Robin
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Stable carbon isotope labelled carbon dioxide as tracer gas for air change rate measurement in a ventilated single zone2017In: Building and Environment, ISSN 0360-1323, E-ISSN 1873-684X, Vol. 115, p. 173-181Article in journal (Refereed)
    Abstract [en]

    Carbon dioxide (CO2) has often been used as tracer gas for measurement of the air change rate l (h1 ) in buildings. In such measurements, a correction is required for the presence of indoor CO2, which commonly consists of atmospheric CO2 mixed with human respired CO2. Here, 13C isotope-labelled CO2 was employed as tracer gas, and cavity ring-down spectroscopy (CRDS) was used for simultaneous measurement of the two isotope analogues 12CO2 and 13CO2. This enabled the simultaneous measurement of the 13CO2 tracer gas, with correction for background 13CO2, and the concentration of indoor CO2, allowing for presence of occupants. The background correction procedure assumes that the isotope delta of the background indoor CO2 equals dB ¼ 19‰, based on the prior information that the carbon isotope ratio RB ¼ 13C/12C of all carbon in the bio-geosphere of earth is in the interval 0.010900 < RB < 0.011237. Evidence supported that l could be accurately measured, using the new 13CO2 tracer method, even when the background 13CO2 concentration varied during the measurement time interval, or when the actual dB value differed from the assumed value. The measurement uncertainty for l was estimated at 3%. Uncertainty in l due to uncertainty in RB, uRB(l), was estimated to increase with a decreasing amount of 13CO2 tracer. This indicated that at least 4 ppm tracer must be used, in order to obtain uRB(l)/l < 2%. The temporal resolution of the l measurement was 1.25/l h.

  • 47.
    Ohlsson, K. E. Anders
    et al.
    Swedish University of Agricultural Sciences, Department of Forest Ecology and Management, Umeå, Sweden.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Quantitative infrared thermography imaging of the density of heat flow rate through a building element surface2014In: Applied Energy, ISSN 0306-2619, E-ISSN 1872-9118, Vol. 134, p. 499-505Article in journal (Refereed)
    Abstract [en]

    Infrared thermography is often used to record an image of the building envelope surface temperature, and thereby acquire qualitative information on its thermal insulation performance. Recently, a thermography method has evolved, which enables quantitative measurement of the 2-dimensional pattern of the density of heat flow rate (q) across the building element surface. However, based on previous estimates of its measurement uncertainty, the capacity of the thermography method to yield accurate results has been questioned. We present here an improved procedure for measurement of q, with an evaluation of measurement errors. The main improvement consists of the simultaneous measurement of surface temperature, surrounding radiative temperature, and air temperature, based on information included in one single thermal camera image. This arrangement allows for accurate measurements of small temperatures differences, and thereby reduced uncertainty in the measurement of q. The measurement bias was evaluated experimentally by a comparison of thermography results against a reference method. Under natural convective conditions, there was a 2.6 W m(-2) constant difference between the two methods. The measurement uncertainty u(q) was estimated as a function of q. Based on this, the lower limit of the measurement working range was determined to be 6 W m(-2), which corresponds to less than 10% relative uncertainty. In the case of forced convection, the thermography method yielded less reliable results. The reason for this was the sensitivity of the results to the choice of model for the convective heat transfer coefficient, and the difficulty to select the position for measurement of the wind speed, which is appropriate for this model.

  • 48.
    Ohlsson, K.E. Anders
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Östin, Ronny
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Sol-air thermometer measurement of heat transfer coefficient at building outdoor surface2018Conference paper (Refereed)
  • 49.
    Ohlsson, K.E. Anders
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Östin, Ronny
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Sol-air thermometer measurement of heat transfer coefficient at building outdoor surface2018In: Energy Procedia, ISSN 1876-6102, E-ISSN 1876-6102, Vol. 132, p. 357-362Article in journal (Refereed)
    Abstract [en]

    Heat flow measurement with a heat flow meter is a standardized method (ISO 9869-1) to estimate thermal transmittance (U-value) of a building element. The heat flow meter is a thin plate mounted on top of the surface of the element, and measures the heat flux q through the plate. The measured q is the product of the difference in temperatures between exterior and interior environment, and the U-value. The heat transferred from the element is based on the radiant and the convective heat transfer.

    ISO 9869-1 specifies that the environment temperature Te “is a notional temperature" and it "cannot be measured directly” (section A.3.1). The air temperature Ta is proposed as a reasonable approximation for the indoor environment, while overcast conditions and absence of significant solar radiation are specified conditions for replacing Te with Ta for the exterior environment.

    The sol-air thermometer (SAT) measures the sol-air temperature Tsa, i.e. the equivalent temperature of the convective and the radiative environment. In the absence of solar radiation, Te = Tsa. SAT is a sensor consisting of a thin flat solid plate, of high thermal conductivity. The front side of the sensor is exposed to the environment, whose Tsa is to be measured, and the backside is thermally insulated. The temperature of the SAT-plate equals Tsa.

    In this work we propose introduction of the measured Te in the existing standard (ISO 9869-1). The method for measurement of Tsa, using the SAT, has been demonstrated experimentally for different periods, without solar radiation present and under stable climatic conditions.

  • 50.
    Ohlsson, K.E. Anders
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Östin, Ronny
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Olofsson, Thomas
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Step-transient method for measurement of the heat transfer coefficient at surfaces exposed to simulated building outdoor environments using the sol-air thermometer2018In: Journal of Building Physics, ISSN 1744-2591, E-ISSN 1744-2583, Vol. 42, no 3, p. 373-387Article in journal (Refereed)
12 1 - 50 of 94
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