| 1. |
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| 2. |
- Harderup, Lars-Erik
(författare)
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Fallstudie i provhus med uteluftventilerat vindsutrymme : Mätningar och simuleringar
- 2022. - 1
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- On a cold-ventilated attic, there is always an outer roof that must be tight against snow and meltwater, which means that there are also materials in the construction that make it more or less vapour tight. In traditional roofs, the waterproofing layer often consists of an asphalt-impregnated paperboard on a tonged and grooved board. As an alternative to the conventional solution, a less diffusion-tight product is used instead. According to (Arfvidsson et al., 2017), this can sometimes be a suitable solution. However, the risk of moisture damage during the construction phase must be considered.Field measurements have been carried out in a test house close to LTH in Lund to investigate whether there will be any differences in the climate on a cold attic and its surrounding building parts with a traditional outer roof compared to a modern product with less vapour resistance. The case study results show no decisive differences in moisture conditions when comparing two different sur-face materials on a tonged and grooved board. The outer roofs examined was traditional roofing felt and a diffusion-open product. In cases where differences could be found, these were small but usually to the advantage of the diffusion-open product.Results from a relatively extensive literature study are reported, with a separate sum¬mary for each report. The literature study shows that the interest in cold roofs ventilated with outdoor air is of great interest, both nationally and inter-nationally. In many cases, approximately the same conclusions are reached. Namely that outdoor ventilated attics are a risk construction, especially if they are well insulated. There is also a warning to additionally insulate existing build-ings without first conducting a thorough analysis of what this can lead to from a humidity point of view. The literature study also contains articles on parallel roofs ventilated with outdoor air and compact roofs with diffusion-open roof coverings. Many reports within this area emphasize the importance of well-thought solutions and careful work execution.
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| 3. |
- Hiller, Carolina
(författare)
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What have residents got to do with it? : Variations in energy use and energy-related behaviours in single-family houses
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- To achieve global energy goals, energy use in residential buildings must decrease. The implementation of technical measures is crucial but alone it is not sufficient; residents need to change their behaviour as well. However, households are not a homogeneous group in terms of their energy use and behaviour; rather, the use varies between households and over time. To promote energy savings in buildings, these variations need to be explored. The main objectives of this thesis were therefore to examine how energy use in single-family houses varied and how energy-related behaviours of households influenced the use of energy. The examined energy variations included changes over time, differences between households and variations of energy use throughout the day. The impact on these variations from the residents' activities and everyday behaviours was studied as well. A partially multidisciplinary approach was employed, whereby the following methods were combined: energy data analyses with interviews, energy performance measurements with calculations, and time-use diaries with energy measurements. A literature review was also conducted. The participating households lived in electrically heated, detached, single-family houses, built in Sweden in the 1980s. The residences spanned three different housing areas, each of which encompassed similar houses.The thesis showed that on an aggregated level, the energy use was stable over years of occupancy. An individual household's energy usage could, however, both increase and decrease over time, depending on several activities occurring over the years. On a group level, the daily electricity load curves differed between weekdays and weekend days, with clear power peaks in the morning and evening on weekdays. That is, during these peak hours the households contributed to potential power deficits in the energy system. Large differences between similar houses' energy use were demonstrated, similar to findings in other research. Differences of a factor of two to three between the highest and lowest energy usages were discovered; for water use, the differences were even greater, namely a factor of six. The studies found that there were many ways to be a high or a low consumer. That is, most of the households exhibited a range of different energy-related behaviours contributing to their energy use. In addition, there was a spread between households in how long they performed various activities. Moreover, the thesis showed a parallel use of electronic devices of the same type, which meant that each household member owned their own set of devices, potentially leading to an increased use of electricity at the household level.The findings in the thesis are of value when measures are designed to encourage residents to save energy and reduce power peaks. By field measurements, the empirical studies provided technical and resident-related information that is useful when estimating and verifying energy use of buildings. Additionally, the thesis contributed to the field of multidisciplinary research on household energy use as both technical and social perspectives were in focus – an approach that not only attempted to measure actual energy data, but also to reveal the behaviours that were concealed behind the data.
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| 4. |
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| 5. |
- Ekström, Tomas
(författare)
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Predicting the Energy Performance of Buildings : A Method using Probabilistic Risk Analysis for Data-driven Decision-support
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- As most countries worldwide continue to mitigate climate change, one area of focus is a building's energy efficiency. Buildings currently account for approximately 40 per cent of the total energy use in the European Union. One solution for reducing the energy demand from buildings is by continually implementing more stringent building regulations. Consequently, the importance of accurate and efficient building performance simulations to predict the energy performance of a building design increases with more stringent regulation reducing the margin of error. However, a performance gap exists between the predicted energy performance and a building's actual energy performance.This research uses the concept of risk, which consists of probability and consequence, to bridge the knowledge gap and explain and predict the energy performance gap. This research aimed to develop and test a method for using a predictive model to quantify a building design's risk level and evaluate design options. The developed method uses probabilistic risk analysis for quantifying and predicting the energy performance of buildings, resulting in a data-driven decision-support when deciding the building design. The method was developed in steps, presented in several studies. The studies used the research strategy of case studies to test the method and compared the outcome against field measurements and was designed to develop, test, verify and validate the method.One case study used the traditional deterministic approach for quantifying energy performance focused on identifying financially viable renovation packages to passive house level and comparing and optimising different energy performance levels for the building stock. The results showed the potential and limitations of the current method for building performance simulations in evaluating the design space and quantifying the energy performance and costs of different design options.An explorative phase followed, identifying alternative methods and comparing these to the traditional deterministic approach based on the knowledge gained. Finally, qualitative methods were used to evaluate and discern when and for what purpose the alternative probabilistic methods might be advantageous to apply.Based on the outcome of this work, the development of the probabilistic risk analysis method began, resulting in several studies focusing on different aspects of the method. The first study developed and tested an experimental version of the method in a case study, verifying the resulting predictive model against field measurements for the energy performance. The outcome showcased the potential with the developed method and identified several aspects needing further investigation and development. One aspect was regarding the accuracy of the predictive model, requiring further investigation into the data quality used as a basis for the model. The other was how to quantify the consequences of not attaining the design criteria and develop the method to compare design options and support the decision-making process using a data-driven approach. However, the data resolution from the field measurements was coarse, reducing the analytical potential by only comparing the aggregated total.Thus, one purpose with the following case study was to increase the resolution to enable additional analytical comparisons and focused on the data quality. The study evaluated how different levels of data quality impact the predictive model's accuracy. The outcome showcased the importance of data quality and the impact on the predictive model.The subsequent study evaluated how to develop the method to include optimising the building design. The implemented optimisation step compares design options and how the stakeholder viewpoints impact the analysis and models' scope when quantifying the risk. Also evaluated was how the selected design criteria impact a project's risk level. The evaluation illustrates how quantifying the risk level could improve the decision-making process, either when deciding on a building design or the design criterion to use.With the outcomes of this project, the probabilistic methods for quantifying energy performance and consequences of decisions and how to apply them are more accessible to the building sector. The main findings from these studies were the benefits of implementing the probabilistic approach to quantify building designs' energy performance and how this could support the decision-makers during the design process while also clarifying the current limitations to overcome. However, this method adds several new dimensions for data gathering, performing the simulations and analysis, and visualising and conveying the results using different plots. Furthermore, instead of providing a single value based on deterministic approaches for predicting the energy performance of a building design, the probabilistic approach provides a distribution of possible outcomes based on empiric data of uncertainties from which to quantify the probability of failure. Finally, the results also showed the importance and impact of data quality and a structured process for gathering data.
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| 6. |
- Linderoth, Oskar
(författare)
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Hydration, pore structure, and related moisture properties of fly ash blended cement-based materials : Experimental methods and laboratory measurements
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Cement-based materials, such as mortar and concrete, are the most employed construction materials in the world. Cement is an important component; it reacts with water to form a glue, called cement paste, which causes the material to harden. Today, cement production accounts for a significant portion of the world’s annual carbon dioxide emissions. Replacing parts of cement with other materials that have cement-like properties, such as fly ash, can help reduce the climatic impact.Fly ash is a residual product from coal-fired power plants that has previously landed on landfills. Replacing part of ordinary cement with fly ash changes the chemical composition and reactivity of the material. Knowledge of how these changes affect material properties is necessary to fabricate long-term durable structures with fly ash blended cement-based materials. This applies not least to the pore structure and related moisture properties because most processes that degrade cement-based materials are both penetrating and moisture dependent. The aim of this study was to contribute new data and knowledge in this area.Unlike ordinary cement, fly ash has little ability to react directly with water. For fly ash to react with water, it depends on the reaction of cement with water. This causes cement-based materials with fly ash to cure more slowly during in the first days. However, this study shows that materials with fly ash have a lower degree of reaction and are more porous well-beyond the first days of curing. The latter part can be partly explained by the fact that the fly ash reaction binds less water than the cement reaction. Instead, fly ash uses part of the products formed by cement for its reaction.Although the volume of pores increases with increasing fly ash replacement, this study shows that the material’s ability to transport water in the vapour and liquid phase decreases. The porous structure in fly ash blended cement-based materials seems to be more heterogeneous and less connective than that in materials with only ordinary cement. This is of considerable practical importance because the ability to transport moisture controls the drying of the material; for example, the time required before moisture-sensitive flooring materials can be applied to a concrete surface.Furthermore, the present study show that fly ash makes the curing and material properties more temperature sensitive. The reaction of fly ash is considerably delayed at low temperature. The effects are similar to those previously documented for ordinary cement during the first days but differ over longer time. For ordinary cement, low temperature leads to the formation of a more homogenous porous structure that allows the reactions to proceed for a longer amount of time. After a long time, materials with ordinary cement cured at low temperature seem to have the most well-developed properties. These long-term effects of low temperature are not observed as clearly for fly ash blended materials. The results highlight that it is especially important to protect structures with fly ash blended cement-based materials from low temperatures.Finally, the laboratory work in this study involved some method development. A new measurement and evaluation routine was employed, to show that heat development can be measured from the reactions between cement (with and without fly ash) and water for up to a year after mixing. Previous studies have argued that this is not possible after the first few weeks of reaction. The results create new opportunities for researchers and the industry to study long-term reactions in cement-based materials. In this study, we also presented a new method for determining the amount of binder (e.g., cement and fly ash) in small samples of cement-based material. The method makes it possible to compare the measurement results for small samples of mortar or concrete obtained from a larger volume of material (i.e., with unknown compositions).
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| 7. |
- von Platten, Jenny
(författare)
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In the Name of Energy Efficiency : Justice and energy poverty in the energy transition of Swedish housing
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The energy transition of housing is accelerating in parallel with economic inequality reaching historically high levels. There is thus an opportunity to reduce inequalities in living conditions, but also a risk that the costs of the transition are unequally distributed and aggravate existing inequalities. In order to seize the opportunity for a just transition, and in tandem enable a meaningful introduction of energy poverty to the Swedish political agenda, the aim of the presented thesis is to explore how the energy transition of Swedish housing is affecting social justice and vulnerability to energy poverty. This is done by novel conceptualisations, that draw on existing theory particularly relevant for the current context, of what a just energy transition of Swedish housing entails, and how energy poverty can be understood in the Swedish context; but also by adding empirical rigour to the discussion in analysing how costs and burdens of the transition have been shared between income groups, and how vulnerabilities to energy poverty are distributed among households. Overall, the findings show that the strong focus on energy efficiency in transition policy tends to structurally burden low-income residents. This could be seen in how low-income residents, who were shown to have low per capita energy use for housing, had carried a disproportionate cost burden for energy retrofitting over the past years; in how new policy imposing cold rent in the worst-performing buildings predominantly affected low-income households, and consequently elevated the risk for energy poverty in an already vulnerable part of the housing stock; and in how flexible energy use is consistently assumed to be an ability equally distributed across society. By incorporating flexibility in the conceptualisation of energy poverty, it could be determined what characteristics of a household contribute to their ability to dodge the current energy price peaks, but also who are most likely to be winners and losers in future energy systems increasingly reliant on demand-side flexibility. In conclusion, the findings in this thesis show that injustices have occurred in the energy transition over the past decade; that these injustices are structural and not coincidental; and that there are risks of injustices continuing to occur and inequality being built into future energy systems. By disclosing the implications of past decisions, the presented thesis provides credible accounts of the need for increased integration of social perspectives in energy policy, and offers practical support for more just pathways ahead. As such, it challenges dominating transition narratives that, in the name of energy efficiency, structurally have put low-income households at the frontline of the energy transition of Swedish housing.
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| 8. |
- Bengtsson, Mathilda, et al.
(författare)
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Metoden ByggF-PST : Tillämpning av ByggaF på tillverkning av prefabricerade småhus i trä. Version 1.0
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Metoden som presenteras i detta dokument är en tillämpning av ByggaF påprefabricerad småhustillverkning av hus med träbaserad stomme kallad:”ByggaF för Prefabricerade småhus med trästomme”, hädanefter omnämnd somByggaF-PST. ByggaF-PST är en metod som säkerställer, dokumenterar ochkommunicerar fuktsäkerheten i hela byggprocessen, från planering tillbruksskede. Metoden innebär ett arbetssätt för att uppfylla samhällets krav påfuktsäkerhet och innehåller rutiner och hjälpmedel för alla aktörer, frånsmåhustillverkare, konsulter, materialleverantörer och entreprenörer.
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| 9. |
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| 10. |
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| 11. |
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| 12. |
- Yang, Yuchen
(författare)
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Climate Change and Residential Energy Use in Europe : Assessing Future Energy Demands and Renewable Generation Potentials
- 2021
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In recent years, climate change and the corresponding expected extreme weather conditions have been widelyrecognized as potential problems. The construction industry is taking various actions to achieve sustainabledevelopment, implement energy conservation strategies, and provide climate change mitigation. In addition tomitigation, it is crucial to adapt to climate change, and to investigate the possible risks and limitations of mitigationstrategies. Although the importance of climate change adaptation is well-understood, there are still challenges inunderstanding and modeling the impacts of climate change, and the consequent risks and extremes.This licentiate dissertation aims to assess the impact of climate change on the building energy performance andindoor thermal comfort in 38 major European cities distributed in five difference climate zones. In addition, this studyalso investigates the potential of renewable energy generation considering solar PV and wind energy generations.To do this, an ensemble of multiple future climate scenarios with high temporal and spatial resolutions have beenused in this work, enabling us to account for climate variations and extreme events. A set of future climate big datagenerated by RCA4 regional climate model (RCM) were used. In total, 13 future climate scenarios covering fiveglobal climate models (GCMs) and three representative concentration pathways (RCP 2.6, RCP 4.5 and RCP 8.5)were used for the 90-year span of 2010-2099, divided into three 30-year periods (2010-2039, 2039-2069 and 2069-2099).Results show that extreme long and short-term climate events can cause significant changes in energy demand,particularly peak loads during extreme events. This work provided more insights into the importance of consideringboth long- and short-term variations of climate, including extreme events, when assessing future energy solutionsand the energy performances of building stocks.The availability of fine temporal and spatial resolution climate datais crucial for assessing the plausible energy demands of buildings; however, it is important consider climateuncertainties, multiple scenarios, and extreme climate events.Finally, the database of results for each city andclimate zone allows decision makers and designers to count for future climate uncertainties in the early stages ofbuilding design.
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| 13. |
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| 14. |
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| 15. |
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| 16. |
- Åhs, Magnus, et al.
(författare)
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The prediction of moisture and temperature distribution in a concrete reactor containment
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The objective in this research has been to predict the current and future moisture and temperature distribution in a concrete reactor containment, RC. The overall objective in this project was to create a model to be able to predict the moisture and temperature distribution in the concrete wall of the RC of a Pressurized Water Reactor, PWR. In addition, one objective was to design a model to simulate the climate exposure through an operational time of about 60 years. In order to accomplish this, the material properties to be used in a transient moisture and heat transfer model had to be estimated.A three dimensional finite element model was developed to simulate the moisture and temperature conditions during the first 30 years of operation and also to predict the coming 30 years of an RC. The model uses the relative humidity as the driving potential. The model also presents methods to take into account the temperature dependency of the moisture properties, such as the moisture fixation i.e. sorption isotherm and the moisture transport properties, i.e. the diffusion coefficient. Thermal properties were considered to be const ant, .i.e. they were assumed not to be affected by the moisture content.The developed hygro-thermal model was applied in COMSOL Multiphysics, a mathematical software, and used in a number of simulations. The model is developed to predict moisture and temperature distributions in a RC when there is a significant temperature gradient through the concrete structure, which is the case in a PWR. The exterior surface of the RC is exposed to the natural climate.The results from the simulated moisture distributions of a concrete RC were compared with results from measurement performed on a Swedish concrete RC, Ringhals. The simulated moisture distributions in this project and the moisture distribution determined on the Swedish concrete RC were found to qualitatively correspond to each other. There was no possibility to compare the moisture distribution quantitatively.
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| 17. |
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| 18. |
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| 19. |
- Adalberth, Karin
(författare)
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Energi för att bygga bruka riva småhus, Bo92 : Den nya trästaden
- 1994
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I denna rapport redovisas energiberäkningar för tre småhus på Bo 92 i Örebro. Syftet med rapporten är att beräkna och analysera det totala energibehovet och mängd byggnadsmaterial från 'vaggan till graven' för småhus. Med det totala energibehovet menas summan av energibehovet under produktion (materialtillverkning, materialtransporter och uppförande av byggnaden), förvaltning (brukande av byggnaden) samt destruktion (rivning och borttransport).
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| 20. |
- Adalberth, Karin
(författare)
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Energianvändning i småhus, Bo92. D. 1, Beräkningar : Den nya trästaden
- 1994
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I denna rapport redovisas teoretiska beräkningar av energibehov till uppvärmning, tappvarmvatten och hushållselektricitet, energitransporter genom småhusens grunder och energiflöden genom köldbryggor. Beräkningarna omfattar 26 småhus på Bo 92 i Örebro med olika typer av grundläggning, värmeisolering, fönster, värme- och ventilationssystem. Beräkningarna har utförts med datorprogrammen ENORM, CRAWL, SLAB och HConP.
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| 21. |
- Adalberth, Karin
(författare)
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Energy Use and Environmental Impact of New Residential Buildings
- 2000
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The objective of this thesis is to investigate the energy use and environmental impact of residential buildings. Seven authentic buildings built in the 1990s in Sweden are investigated. They are analysed according to energy use and environmental impact during their life cycle: manufacture of building materials, transport of building materials and components to the building site, erection to a building, occupancy, maintenance and renovation, and finally demolition and removal of debris. Results show that approx. 85 % of the total estimated energy use during the life cycle is used during the occupation phase. The energy used to manufacture building and installation materials constitutes approx. 15 % of the total energy use. 70-90 % of the total environmental impact arises during the occupation phase, while the manufacture of construction and installation materials constitutes 10-20 %. In conclusion, the energy use and environmental impact during the occupation phase make up a majority of the total. At the end of the thesis, a tool is presented which helps designers and clients predict the energy use during the occupation phase for a future multi-family building before any constructional or installation drawings are made. In this way, different thermal properties may be elaborated in order to receive an energy-efficient and environmentally adapted dwelling.
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| 22. |
- Adalberth, Karin
(författare)
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Energy Use in Multi-Family Dwellings during their Life Cycle
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this study is to analyse the total use of energy in four multi-family houses during their life cycles, and to compare the use of energy during the different periods in the life cycle. The aim is also to investigate how energy use during the life cycle changes with different construction parts, e g if the thermal insulation thickness or the framework is changed. Results show that the energy used to manufacture building and installation materials during the production phase is approx. 800-1,200 kWh m2 usable floor area. This corresponds to 10-15 per cent of the total energy use during the life cycle. A majority of the energy is used during the period of occupancy for e g space heating, ventilation, domestic hot water production, household electricity and lighting. During this period 5,000-7,500 kWh/m2 usable floor area is used (the life span of the occupancy is assumed to be 50 years). The energy use during this period equals 80-85 per cent of the total use during the life cycle. Results also show a small difference between buildings with different kinds of framework. The difference is very small. It is thus impossible to conclude that one framework is more energy- efficient than another. Instead, the best way to design an energy-efficient building would be to install a heat recovery system in the exhaust air and use windows with a low U value. These solutions may decrease the total energy use during the whole life cycle for one of the studied houses, by 13 and 6 per cent respectively.
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| 23. |
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| 24. |
- Alexanderson, Johan
(författare)
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Secondary emissions from alkali attack on adhesives and PVC floorings
- 2004
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The report describes three investigations of emissions from alkali attack on adhesives and floorings. The investigations show that low alkali levelling compounds, based on calcium aluminate cement, can act as a protection against secondary emissions of 1-butanol and 2-ethylhexanol, provided that the humidity does not exceed a critical level, which with some safety margin is recommended to be 90% RH. Five tested levelling compounds all had the same principal behaviour. A minimum thickness of the levelling compound is recommended to be 5 mm, although the investigations show that the levelling compounds also had protection capacity at 2 mm. One way of assuring that the humidity is below the critical level is to use self-desiccating concrete. A concrete with water-binder ratio of 0.43 together with a levelling compound proved effective.
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| 25. |
- Anderberg, Anders
(författare)
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Studies of moisture and alkalinity in self-levelling flooring compounds
- 2007
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In recent decades there has been an increasing interest in the indoor environment and its connections with public health. One important topic discussed has been the relation between the moisture in buildings and health. Cementitious materials, when cast, contain excess water since this is necessary for workability and for flow properties. The pore solutions in cementitious materials, besides being high in water content, often have a high pH. High-moisture conditions can cause biological growth. A combination of high moisture conditions and high pH can also result in chemical degradation of other materials, affecting both indoor environment and the technical functioning and appearance of the materials involved. Self-levelling flooring compounds (SLCs) that provide smooth horizontal surfaces are used to level the substrates (mainly concrete slabs) before floor coverings are applied. Although such compounds are used extensively, only limited research on their moisture and alkali properties and their functioning in floor constructions has thus far been conducted. The aim of the present study was to investigate the moisture and alkali properties of SLCs and gain a better understanding of their interaction with other materials in floor constructions. Many traditional methods of determining the moisture properties of building materials are time-consuming and are unsuitable for SLCs. Within the project, new methods, such as a rapid method for the simultaneous determination of both the moisture sorption isotherms and of diffusion coefficients, were developed. Measurements were performed of such moisture properties as the chemical binding of water, the physical binding of it (the moisture sorption isotherm), moisture transport (diffusion), and the rate of surface evaporation and of moisture transport to a concrete substrate, with the aim of better understanding the drying behaviour involved and enabling predictions of the long-term moisture state of SLCs to be obtained. The results served as the basis for a drying model that was developed into a computer-based simulation programme for predicting drying times and long-term moisture states of SLCs. Only very low rates for the transport of hydroxide ions from the concrete substrates to the SLCs and within SLCs were found to occur. This implies that SLCs can be used as barriers for protecting floor coverings and floor adhesives from the high pH of concrete. The alkaline degradation of floor adhesives is dependent upon the pH (hydroxide ion concentration) in the zone of contact of the adhesives with the substrate. Secondary emissions from a floor construction due to alkaline degradation are thus dependent upon the pH-level and the transport of hydroxide ions in the substrate. For highly alkaline substrates, such as concrete, carbonation is essential for avoiding degradation of sensitive materials. This is not the case for SLCs that have considerably lower pH. The carbonated layer at the concrete surface may, however, due to its limited thickness, be unable to serve as a long-term protection in terms of secondary emissions. This is better provided by an SLC of lower alkalinity.
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| 26. |
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| 27. |
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| 28. |
- Arfvidsson, Jesper
(författare)
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Moisture Transport in Porous Media. Modelling Based on Kirchhoff Potentials
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The work presented in this thesis is focused on the development of the new concept to describe isothermal moisture transport using Kirchhoff potentials. The first four papers deal with moisture transport in porous media using Kirchhoff potentials. The last three papers deal with wood. Here the theory is extended to the case of anisotropic moisture transport. The seven papers have the following contents: I The theoretical, numerical and computational basis for isothermal moisture transport in building materials using Kirchhoff potentials is described. It is shown that Kirchhoff potentials simplify the whole process from measurement via mathematical and numerical modelling to numerical calculations. II A fast transient technique for determining the diffusion coefficients in hygroscopic materials is presented. A sample of the material is subjected to a staircase function of steps of relative humidity and the moisture uptake is measured by continuous weighing. III The paper presents a method to calculate the moisture penetration depth and the medium moisture level in a material subjected to a periodic relative humidity variation at the boundary. The moisture flow process may be highly non-linear. IV A method to determine the sorption coefficient in a semi-infinite region is presented. A Boltzmann solution for piece-wise linear transport data is used. For the special case of linear data in two-intervals, explicit formulas to get the sorption coefficient are given. V A theory based on the use of Kirchhoff potentials to calculate moisture flow in wood is presented. Anisotropy is allowed for using different flow coefficients in the different directions, in both sapwood and heartwood. VI The paper presents a calculation procedure and a two-dimensional PC-model especially designed for drying of wood. The model accounts for different moisture flow coefficients in radial and tangential directions for both sapwood and heartwood. Calculation results from the model are compared with independently measured two-dimensional moisture distributions. The agreement was good. VII Measurements of moisture content distributions were performed during drying of Scots pine (Pinus sylvestris). The measurements were done in heartwood and sapwood separately and in all three directions to grain separately A new method evaluate flow coefficients from transient measurements is presented.
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| 29. |
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| 30. |
- Bagge, Hans
(författare)
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Building Performance - Methods for Improved Prediction and Verification of Energy Use and Indoor Climate
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Reducing CO2 emissions is one of the most important goals in Europe as well as the rest of the world. To reach that goal, the use of energy must be reduced. Thus, the building industry is facing a great challenge. Not only energy efficiency but also sustainability is desirable in the building stock. This thesis presents and suggests methods that can be used to improve prediction and verification of building performance regarding energy use and indoor climate. Predictions of energy use and indoor climate generally do not agree with results from measurements in buildings during operation. These discrepancies are counter-productive to the implementation of energy-efficiency and sustainability measures. This thesis addresses these issues and suggests viable partial-solutions to the problems encountered. This research project has measured several energy use and indoor climate related parameters in multi-family buildings in Sweden. The monitoring was frequent, at least once per hour, and the measurements lasted at least one year, which makes it possible to present reference data for the measured parameters and their variations on different time scales and during different conditions. Based on the analysis of the measurements, several methods offering partial-solutions on different levels to the addressed problems have been developed. Examples of these methods are: • A method to assess useful solar heat gains in actual buildings during operation. • A method to assess window airing and air leakage in actual buildings during operation. • A method to assess occupancy level in actual buildings during operation. • Methods to generate hourly input data on hygrothermal conditions that take into account both outdoor conditions and user behaviour. • A method to make meteorological corrections to energy use that takes into account several outdoor climate parameters and the characteristics of the building concerned. The methods aim to describe reality more accurately and can be applied to predictions and verifications. The methods are fully developed and ready to use in practice. These methods together with the discussion and argumentation in this thesis provide the building sector with useful and positivistic recommendations. If these are used, it is believed that it will be possible to increase the quality of predictions and verifications, and agreement between them, as well as to provide buildings displaying increased sustainability, with low energy use and good indoor climate.
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| 31. |
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| 32. |
- Berggren, Jonas, et al.
(författare)
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1980-talets lågenergihus: hur fungerar de efter tio år
- 1997
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Syftet med detta forskningsprojekt är att undersöka hur ett antal väl dokumenterade experimenthus har fungerat under en tioårsperiod. Undersökningen jämför i första hand uppgifter om energianvändning och de driftfrågor som hör till energianvändningen. Vidare har de boendes upplevda inomhusklimat studerats för att kunna se om, och i så fall hur, experimenthusens låga energianvändning har påverkat det upplevda inomhusklimatet.
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| 33. |
- Blomberg, Thomas
(författare)
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Heat conduction in two and three dimensions : computer modelling of building physics applications
- 1996
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The first aim of this doctoral work has been to develop a new generation of computer programs for transient and steady-state heat conduction in two and three dimensions. A large range of heat transfer problems within the field of buildings physics can be analyzed using these tools. There are, however, many things to keep in mind when modelling a problem, such as how to choose the numerical mesh, the proper boundary conditions, numerical accuracy, numerical stability, etc. The second aim of the thesis is to provide advice and guidelines how to deal with various problems that occur in building physics applications. To this aim, a large part is devoted to specific problems. The third aim of the thesis is to address a number of particular topics and problems: Numerical accuracy, successive over-relaxation, methods to increase accuracy by combining results from calculations using different numerical meshes, solution of large three-dimensional problems, solution of problems with large difference in thermal conductivity (steel versus insulation), heat conduction coupled to radiation in cavities, how to obtain a proper U-value for a foundation with floor heating, etc. The robust method of explicit finite differences is used. This method closely follows the physical equations. The mathematical equations for two- and three-dimensional heat conduction and the numerical formulation are presented. The numerical error for different meshes is studied and compared with analytical solutions. The effectiveness of the method of successive over-relaxation is demonstrated, while the gain using "successive subdivision'' is modest. Results from calculations with two or three different meshes may be used to estimate more accurate results. The gain using this technique can be quite substantial. The problem of thermal radiation in a cavity coupled to heat conduction and ventilation is analyzed in detail. The presented equations are well suited for an iterative computer solution procedure, which turns out to be robust and very rapid.
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| 34. |
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| 35. |
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| 36. |
- Burke, Stephen
(författare)
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Building Physics Tools: Needs, Use and the Lack of Use in the Building Process. Modelling Non-Isothermal Moisture Flow and Frost Penetration
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Despite advances in material science, computers and building technology, building failures related to building physics continue to occur. These failures range from a building not meeting its energy use target to a building causing people to become ill from exposure to various chemicals or biological organisms. These failures cost society considerable amounts of money each year and many of these failures are preventable already during the design stage of the building process. This thesis looks at some of the costs associated with building failures due to moisture problems and explores the reasons why these failures are persistent in the building industry. This is done by looking at the role of computer based tools, interviewing moisture consultants, analysing how they operate and what limitations both they, and the tools they use, have. One result in this thesis shows that a considerable amount of money is spent on repairing moisture damages in buildings. Another result is that the consultants who can prevent these problems are not able to accumulate experience due to a poor management system which only focuses on profit and not the development of the consultants. Building physics tools are not used due to high costs, usability issues or inadequate information regarding the use of the tool. A system of operation is proposed in the thesis which can make experience meaningful to consultants. The tools themselves are limited by deficiencies in moisture transport theory which cannot take into account non-isothermal moisture transport or variable thermal properties. Some of the problems with non-isothermal moisture models are discussed and new ways to improve such models are proposed in this thesis.
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| 37. |
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| 38. |
- Burström, Per Gunnar
(författare)
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Beständighet och åldring hos fogmassor
- 1976
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- De grundläggande åldringsfaktorernas inverkan på vanliga typer av fogmassor. Samband mellan accelererade åldringsmetoder och naturlig åldring.
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| 39. |
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| 40. |
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| 41. |
- Ekström, Tomas
(författare)
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Leaching of concrete : the leaching process and its effects
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The present report presents an experimental study of leaching of concrete caused by water percolating through the concrete, or by diffusion from concrete to external water in contact. An apparatus was designed and constructed in which de-ionised water could be forced, by external pressure, through a number of concrete specimens of differing characteristics. It was found that, whereas the initial water flow was normally low and uniform, most specimens showed a rapid increase in water flow after a certain period of time. This was probably due to formation of certain distinct percolation channels. The solid material around these channels was leached, the concrete becoming disintegrated, and almost no continuous cementitious material being left to maintain strength and tightness of the concrete. The chemical composition of the percolated water was analysed, making it possible to calculate the amount of leaching and consequently to theoretically assess the increase in porosity and reduction of strength Changes in the structure of concrete caused by leaching were also investigated experimentally by measurements of porosity, pore size distribution and strength. ESEM-EDX-studies were made in order to find out the morphology of leached concrete. Results from all these experimental studies are presented in the report. A theoretical model of the leaching process and its effects on the material and on the structural stability of real structures was developed. The model is applied to the experimental data.
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| 42. |
- Engdahl, Fredrik
(författare)
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Air - for Health and Comfort, An Analysis of HVAC Systems' Performance in Theory and Practice
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- One part of the objective is to analyze how different ventilation systems perform in practice when it comes to supplying and exhausting designed air flow in different outdoor and indoor conditions. The other part is to analyze the design criterias and the energy use of a variable air volume system based on controlled static pressure at the branch duct level and supplying outdoor air only. To investigate the technical status of ventilation systems, the result from the compulsory testing and examination of ventilation systems (OVK) is used. A multi-zone model (COMIS) is used to study the air flow in a multi-family building. Two ventilation systems are analyzed with the same building; the mechanical exhaust and the mechanical supply and exhaust system. Fundamental pressure loss equations, measurements and a computer program are used to determine how much the air flow at the air terminals on a branch with controlled static pressure differs. A model is developed to determine the optimal supply air temperature with respect to energy use. An average of 34% of the studied ventilation systems performed as intended. Both the mechanical exhaust and the mechanical supply and exhaust air system showed sensitiveness to outdoor temperature, building airtightness and wind. When the static pressure is controlled to be constant at the branch duct level it is possible to vary the air flow to different zones without measuring the individual flow and without significantly influence the air flow to other zones. When using 100% outdoor air the indoor air quality will be improved during most of the year. There is a great potential in controlling the supply air temperature optimally to reduce the energy use.
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| 43. |
- Fagerlund, Göran
(författare)
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A service life model for internal frost damage in concrete
- 2004
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The idea behind the service life model presented in this report was published in 1979. It has thereafter been described and developed in a number of reports and papers. The basis of the model is the observation that a well-defined critical, or maximum allowable, moisture content exists, above which the material is severely damaged by frost, and below which it is unharmed also when freezing is repeated at numerous occasions. This means that there is an analogy between design with regard to frost resistance and design with regard to structural safety. The critical moisture condition corresponds to the fracture load at structural design, whilst the real moisture condition corresponds to the actual load in structural design - the load effect. This also means that design with regard to frost resistance is to a high extent a moisture mechanics problem - one must be able to predict the future moisture variation in all parts of the structure. The analogy with structural design means that the same theory can be used for calculation of the probability of frost damage as for the risk of structural failure. The report focuses on the moisture mechanics part of the problem - i.e. the load part. The possibility to predict moisture by theoretical calculation is evaluated, and found to be small.
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| 44. |
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| 45. |
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| 46. |
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| 47. |
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| 48. |
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