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Multi-dimensional approach used for energy and indoor climate evaluation applied to a low-energy building
Linköping University, Department of Management and Engineering, Energy Systems. Linköping University, The Institute of Technology.
2006 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The building sector alone accounts for almost 40% of the total energy demand and people spend more than 80% of their time indoors. Reducing energy demand in buildings is essential to the achievement of a sustainable built environment. At the same time, it is important to not deteriorate people’s health, well-being and comfort in buildings. Thus, designing healthy and energy-efficient buildings is one of the most challenging tasks. Evaluation of buildings with a broad perspective can give further opportunities for energy savings and improvement of the indoor climate.

The aim of this thesis is to understand the functionality, regarding indoor climate and energy performance, of a low-energy building. To achieve this, a multi-dimensional approach is used, which means that the building is investigated from several points of views and with different methods. A systems approach is applied where the definition of the system, its components and the border to its environment, is essential to the understanding of a phenomenon. Measurement of physical variables, simulations, and qualitative interviews are used to characterize the performance of the building. Both energy simulation and computational fluid dynamic simulations are used to analyse the energy performance at the building level as well as the indoor climate at room level. To reveal the environmental impact of the low-energy building studied in this thesis the CO2 emissions and embodied energy have been investigated regarding different surrounding energy systems. The evaluated building is situated at the west coast of Sweden and uses about 50% of energy compared to a comparable ordinary Swedish building. The building is well-insulated and an air-to-air heat exchanger is used to minimise the heat losses through ventilation. The houses are heated mainly by the emissions from the household appliances, occupants, and by solar irradiation. During cold days an integrated electrical heater of 900 W can be used to heat the air that is distributed through the ventilation system. According to measurements and simulations, the ventilation efficiency and thermal environment could be further improved but the occupants are mostly satisfied with the indoor climate. The control of the heating system and the possibility for efficient ventilation during summertime are other important issues. This was found through quantitative measurements, simulations and qualitative interviews. The low-energy building gives rise to lower CO2 emissions than comparable buildings, but another energy carrier, such as district heating or biofuel, could be used to further improve the environmental performance of the building. The total energy demand, including the embodied energy, is lower than for a comparable building.

To understand the functionality of a low-energy building both the technical systems and the occupants, who are essential for low-energy buildings, partly as heat sources but mainly as users of the technical systems, should be included in the analysis.

Place, publisher, year, edition, pages
Institutionen för konstruktions- och produktionsteknik , 2006.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1065
Keyword [en]
Low-energy building; energy; indoor climate; simulation
Keyword [sv]
Lågenergihus; energi; inomhusklimat; simulering
National Category
Building Technologies
Identifiers
URN: urn:nbn:se:liu:diva-7819ISBN: 91-85643-21-1 (print)OAI: oai:DiVA.org:liu-7819DiVA: diva2:22754
Public defence
2006-12-15, C3, Hus C, Linköpings universitet, Linköping, 10:15 (English)
Opponent
Supervisors
Available from: 2006-11-30 Created: 2006-11-30 Last updated: 2009-03-02
List of papers
1. Energy usage and thermal environment in a low-energy building
Open this publication in new window or tab >>Energy usage and thermal environment in a low-energy building
2004 (English)In: Proceedings of Roomvent 2004, 9th International Conference on Air Distribution in Rooms, 5–8 Sept., Coimbra, Portugal, 2004Conference paper, Published paper (Refereed)
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-14149 (URN)
Available from: 2006-11-30 Created: 2006-11-30 Last updated: 2009-02-18
2. Energy demand and indoor climate in a low energy building : changed control strategies and boundary conditions
Open this publication in new window or tab >>Energy demand and indoor climate in a low energy building : changed control strategies and boundary conditions
2006 (English)In: Energy and Buildings, ISSN 0378-7788, Vol. 38, no 4, 315-326 p.Article in journal (Refereed) Published
Abstract [en]

Energy demand in the built environment is an important issue. In Sweden, 39% of energy use originates from the building sector, and this figure is increasing. Several attempts have been made to improve the energy use, for example low-energy houses, which are built with the aim of decreasing the use of energy, but still providing a good environment for the occupants. An energy simulation program, ESP-r, was used for simulation of the energy requirement and indoor climate in a well-insulated terraced house in Sweden. The building model was compared to measured values from the real object. A computational fluid dynamics (CFD)-model for one room was used to simulate and visualize the airflow and temperature pattern. Increased set-point temperature increases the power demand by about 200 kWh/°C. Thinner insulation increases the heat demand but decreases the demand for passive cooling by airing and deteriorates the indoor climate. Different types of windows affect both the energy demand and the indoor climate significantly. Load management was simulated by restriction on the heating possibilities and an economical comparison was made to investigate the advantage of such an operation. The extra insulation has a payoff time of about 38 years at common Swedish energy prices.

Keyword
Low-energy building; Energy simulation
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-14150 (URN)10.1016/j.enbuild.2005.06.013 (DOI)
Available from: 2006-11-30 Created: 2006-11-30 Last updated: 2009-11-16
3. Indoor climate in low-energy houses: An interdisciplinary investigation
Open this publication in new window or tab >>Indoor climate in low-energy houses: An interdisciplinary investigation
2006 (English)In: Building and Environment, ISSN 0360-1323, Vol. 41, no 12, 1678-1690 p.Article in journal (Refereed) Published
Abstract [en]

If energy demand in the building sector should be decreased, low-energy buildings, which are built with the aim of decreasing the use of energy, but still provide a good environment for the occupants, ought to be built on a larger scale. Investigations into how experimental houses function provides the opportunity of improving next-generation houses. This paper presents the results of an interdisciplinary investigation of the thermal environment and the space heating in 20 low-energy terraced houses. Qualitative interviews with the occupants as well as measurements of physical parameters have been conducted for this purpose. When the houses are inhabited and household appliances and candles are being used, the temperature can be managed within acceptable limits, even on cold days. However, those living in middle houses are generally more satisfied with their indoor temperature than the households of the gable houses. Results from both interviews and measurements show that there is a temperature difference between the floor levels, which is more pronounced in the gable houses. One outcome of the investigation is that information about the functionality of the heating system given to the households should be improved. Another outcome is that the accuracy of the temperature regulation system could be better.

Keyword
Indoor climate; Interdisciplinary method; Temperature measurements; Low-energy houses; Occupier satisfaction; Comfort; Sociotechnical system
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-14151 (URN)10.1016/j.buildenv.2005.06.022 (DOI)
Available from: 2006-11-30 Created: 2006-11-30
4. Experimental evaluation of airflow in a low-energy building
Open this publication in new window or tab >>Experimental evaluation of airflow in a low-energy building
2006 (English)In: The International Journal of Ventilation, ISSN 1473-3315, Vol. 5, no 2, 239-248 p.Article in journal (Other academic) Published
Abstract [en]

This paper reports on tracer gas measurements of the ventilation flow within a low-energy building. Constant-concentration, decay and homogenous tracer gas emission methods were used. Low-energy buildings are airtight constructions; effective ventilation is thus very essential for the indoor climate. The results of this study show an airflow rate between 0.42 and 0.68 air exchanges per hour (ac/h), which should be compared to the minimum requirements in Sweden of 0.5 ac/h. It was found that the airflow changes with time and that the local mean age of air was different on different floors of the building and, to some extent, different at different heights.

Keyword
ventilation, low-energy building, tracer gas, constant concentration, decay, homogenous concentration emission, dwellings
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-14152 (URN)
Available from: 2006-11-30 Created: 2006-11-30 Last updated: 2009-03-10
5. A comprehensive investigation of a low-energy building in Sweden
Open this publication in new window or tab >>A comprehensive investigation of a low-energy building in Sweden
2007 (English)In: Renewable Energy, ISSN 0960-1481, Vol. 32, no 11, 1830-1841 p.Article in journal (Refereed) Published
Abstract [en]

In Sweden, the building sector alone accounts for almost 40% of the total energy demand and people spend more than 80% of their time indoors. Reducing energy demand in the buildings is essential to the achievement of a sustainable built environment. At the same time, it is important to not deteriorate people's health, well-being and comfort in buildings. Thus, designing healthy and energy efficient buildings are one of the most challenging tasks for building scientists. A low-energy building that uses less than half of the purchased energy of a comparable typical Swedish building has been investigated from different viewpoints in an attempt to represent the building at different system levels. First, the ventilation performance in different rooms using the tracer gas method is reported. Second, results from simulations and in situ measurements are used to analyse the building's power demand and energy performance. The household's behaviour and their impact on energy usage as well as acceptance are reported. Finally, the CO2 emissions with regard to the energy usage are analysed on the basis of different supply energy forms from surrounding energy systems, for example a Swedish and European electricity mix, or district heating as a substitute for electrical heating.

Keyword
Low-energy building, Ventilation, Indoor climate, Energy use, Environmental performance
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-14153 (URN)10.1016/j.renene.2006.10.009 (DOI)
Available from: 2006-11-30 Created: 2006-11-30 Last updated: 2009-05-04
6. CFD simulation of temperature and airflow pattern in a low-energy building
Open this publication in new window or tab >>CFD simulation of temperature and airflow pattern in a low-energy building
Manuscript (Other academic)
Identifiers
urn:nbn:se:liu:diva-14154 (URN)
Available from: 2006-11-30 Created: 2006-11-30 Last updated: 2010-01-13
7. Measured and predicted energy demand of a low energy building: Important aspects when using Building Energy Simulation
Open this publication in new window or tab >>Measured and predicted energy demand of a low energy building: Important aspects when using Building Energy Simulation
2007 (English)In: Building services engineering research and technology, ISSN 0143-6244, Vol. 28, no 3, 223 -235 p.Article in journal (Refereed) Published
Abstract [en]

Three different simulation tools were used to simulate a low energy terraced house in the south of Sweden. The software tools all use dynamic models to calculate, for example, the energy demand for heating and the indoor temperatures. The aim of this paper is to discuss the relative importance to the annual energy demand of different energy aspects of a Swedish low-energy house. Both measured and simulated values are considered and compared. The focus is on the impact of choice of software, the habits of the tenants, and the relative impact of different design parameters such as ventilation rates.The measured values for total electricity demand range from about 6000 kWh to over 12 000 kWh, the average demand being 8020 kWh. The annual predicted total energy demand using three different simulation software tools deviated by about 2%. The energy use deviation due to airflow control was about 10%, and the deviation due to differences in heat exchanger efficiency was about 20% and the deviation in annual energy use due to differences in internal gains due to differences in tenant habits, assumed in the models, was 7%.Furthermore, when comparing the predicted energy use during the design process of the low-energy building with actual measurements after the tenants have moved in, these differ about 50% in average for this specific case.Practical application: Building energy simulation software is often used to make predictions of how different construction materials, design principles and operation influence the energy balance and indoor thermal comfort. It is therefore important that the output of these software tools is trustworthy and accurate. This paper discusses the importance of accurate input data during the design process in order to achieve a valid prediction of energy use with emphasis on tenants' behaviour. It was shown that the deviations in a parametric study were larger than the deviations in the comparison between the results from the three simulation tools. This indicates a need for more accurate models for modelling tenant behaviour and habits rather than more accurate building component models.

Place, publisher, year, edition, pages
SAGE Journals Online, 2007
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-14155 (URN)10.1177/0143624407077393 (DOI)
Available from: 2008-11-14 Created: 2008-11-14 Last updated: 2009-05-04Bibliographically approved

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