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| 2. |
- Bülow-Hübe, Helena
(författare)
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Energy Efficient Window Systems. Effects on Energy Use and Daylight in Buildings.
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis deals with energy-efficient windows in Swedish buildings. Parametric studies were performed in the dynamic energy simulation tool Derob-LTH in order to study the effects of window choices on energy use and indoor climate for both residential and office buildings. A steady-state program was used to evaluate two years of measurements of energy use and indoor temperatures of an energy-efficient row-house. Two behavioural studies regarding (1) daylight transmittance, view and room perception using super-insulated windows and (2) the satisfaction with the daylight environment and the use of shading devices in response to daylight/sunlight were conducted in full-scale laboratory environments exposed to the natural climate. Results show that as the energy-efficiency of buildings increase, window U-values must decrease in order not to increase the annual heating demand, since the heating season is shortened, and useful solar gains become smaller. For single-family houses with a window-to-floor area ratio of 15 % and insulated according the current Swedish building code, the U-values should thus on average be lower than 1.0 W/m²K. For houses insulated according to 1960s standard, the U-value may on average be 1.6 W/m²K. For colder climates (northern Sweden), the U-values should be somewhat lower, while slightly higher U-values can be tolerated in milder climates of south Sweden. Thermal comfort during winter is improved for energy-efficient windows. However, overheating problems exist for both super-insulated houses and highly glazed office buildings showing a need for very low U-values in combination with low g-values. Daylight experiments indicate that the use of two low-emittance coatings tints the transmitted daylight enough to be appreciated, and colours may be perceived as more drab and rooms more enclosed. A compromise between energy-efficiency and daylighting may be needed, and it is suggested that only one coating be used except when very high energy-efficiency is required.
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| 3. |
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| 4. |
- Dahlblom, Mats
(författare)
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Material- och energiflöden i VVS-installationer : fallstudie
- 1999
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Denna litteraturstudie utgör andra etappen i ett licentiatarbete om utbytbarhet, material- och energiflöden för installationer i byggnader (Orsaker till byte av VVS-installationer; TABK--01/1020).
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| 5. |
- Dahlblom, Mats, et al.
(författare)
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Småhus med installationsgrund: utvärdering av experimenthus i Halmstad
- 1997
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I denna rapport redovisas resultaten från mätningar utförda i ett experimenthus i Halmstad som är grundlagt med den så kallade installationsgrunden enligt EG-2000 konceptet. Insamlade mätdata används för beräkningar av energianvändningen och energibalansen. Energianvändningen i experimenthuset jämförs med energianvändningen i ett liknande hus grundlagt med platta på mark.
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| 6. |
- Dubois, Marie-Claude
(författare)
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Solar Shading for Low Energy Use and Daylight Quality in Offices: Simulations, Measurements and Design Tools.
- 2001
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis investigates the impact of solar shading devices on energy use and daylight quality in office rooms. The impact on energy use is analysed through computer simulations with the dynamic energy simulation program Derob-LTH while the impact on daylight quality is investigated through measurements in full-scale experimental office rooms and simulations with the program Radiance. This thesis also includes a literature review of research on solar shading as well as design tools to incorporate shading devices at an early stage in the design of buildings. This thesis indicates that, in cold countries, shading devices may provide more annual energy savings than any solar-protective (reflective, tinted) glazing and that the optimum glazing transmittance is orientation- and climate-dependent. For example, high annual energy savings are obtained on the south facade with higher transmittance glazings (compared with the east and west facade) because the potential for passive solar gain utilisation in the winter is high in comparison with the annual cooling demand. Exterior shading devices like awnings and overhangs may reduce the cooling demand dramatically but they are not suitable as daylight (glare) control devices. Devices like screens and venetian blinds are preferable because they cover the entire window area, which prevents sunlight patches in the room and the direct view of the bright sky. Screens and venetian blinds also reduce daylight in the room to levels that are suitable for computer work. However, it is essential that the screen be of a diffusing type since screens with a strong (specular) transmittance component result in poor daylight quality. The study on daylight quality also indicated that a screen transmittance of around 15 % may be optimum for a standard (3.5 by 6.0 m2) south-oriented office room with a window covering around 25 % of the facade area (12 % of the floor area).
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| 7. |
- Fredlund, Bertil, et al.
(författare)
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Resultatredovisning av BFR-finansierad forskning : 1994-1996
- 1997
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Rapporten utgör en sammanfattning av verksamheten som bedrivits av institutionen för Byggnadskonstruktionslära, LTH, under perioden 1994-01-01 - 1996-12-31 med forskningsanslag från Byggforskningsrådet i ämnena Byggnadskonstruktion (BFR-projekt nr 930930-7) och Installationsteknik (BFR-projekt nr 930958-3). Redovisningen koncentreras på resultatredovisning från delprojekten.
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| 8. |
- Håkansson, Håkan
(författare)
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Retarded sorption in wood : experimental study, analyses and modeling
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Models of moisture flow processes in wood are normally based on a Fickian approach. In many instances, there are considerable discrepancies between modelling and experimental results. It is shown in this thesis that a major cause for these discrepancies is a so-called retarded sorption which is not accounted for in conventional theories. This retarded sorption occurs in the wood cell wall. A special experimental set-up to isolate and measure this process has been developed. Extensive series of sorption response measurements with different sequences of relative humidities have been performed on very thin, well exposed wood samples. The results show that the sorption often has an intricate dependence on moisture history. Two small steps may not give the same sorption as the corresponding single larger step. The process is not linear. The part of the sorption that is retarded is especially large at high relative humidities. The retarded sorption increases with decreasing temperature. In special cases, retarded sorption for single cell walls with a time scale of more than a month has been observed. Different models to reproduce the measured results have been tested. It is shown that models with one added internal node are not sufficient. A few internal nodes are needed. The conductances between the nodes must be decreasing inwards. Non-linear conductances, where the conductance increases with the difference in moisture state between the nodes, are required to reproduce the result for more irregular sequences of relative humidity. The best agreement was obtained with a non-linear model with five internal nodes, where the inner-most node accounted for hysteresis. Tangential and radial swelling (and shrinkage) was measured in parallel for two series. The ratio between radial and tangential swelling was quite constant throughout the whole series with their many and varied changes of relative humidity. The variation in time of tangential swelling and moisture content followed each other quite well along lines with a constant slope, in particular for cyclic steps. A somewhat higher slope was obtained in all cases where the sorption contained a larger retarded part.
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| 11. |
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| 12. |
- Källblad, Kurt
(författare)
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Thermal models of buildings : determination of temperatures, heating and cooling loads : theories, models and computer programs
- 1998
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The need to estimate indoor temperatures, heating or cooling load and energy requirements for buildings arises in many stages of a buildings life cycle, e.g. at the early layout stage, during the design of a building and for energy retrofitting planning. Other purposes are to meat the authorities requirements given in building codes. All these situations require good calculation methods. The main purpose of this report is to present the authors work with problems related to thermal models and calculation methods for determination of temperatures and heating or cooling loads in buildings. Thus the major part of the report deals with treatment of solar radiation in glazing systems, shading of solar and sky radiation and the computer program JULOTTA used to simulate the thermal behavior of rooms and buildings. Other parts of thermal models of buildings are more briefly discussed and included in order to give an overview of existing problems and available solutions. A brief presentation of how thermal models can be build up is also given and it is a hope that the report can be useful as an introduction to this part of building physics as well as during development of calculation methods and computer programs. The report may also serve as a help for the users of energy related programs. Independent of which method or program a user choose to work with it is his or her own responsibility to understand the limits of the tool, else wrong conclusions may be drawn from the results.
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| 13. |
- Nordquist, Birgitta
(författare)
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Goda exempel på sunda hus, daghem och skolor
- 1995
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- I denna rapport redovisas nio daghem och åtta skolor i vilka brukarna upplever ett tillfredsställande inneklimat. Både ny- och ombyggda objekt behandlas. Varje objekt redovisas med syfte, organisation av byggprocessen, bakgrundsfakta om byggnaden, produktions- och driftskostnader, tekniska fakta om konstruktion, material, värme och ventilation, energianvändning, städvanor samt utvärdering av enkäter och mätningar.
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| 14. |
- Nordquist, Birgitta
(författare)
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Ventilation and window opening in schools, Experiments and Analysis
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The objective of this thesis is to study the application of ventilation in schools buildings. A number of studies of the application of different forms of ventilation are presented. The main part of the thesis focuses on window opening in a classroom. Analytical models for calculation of the air change caused by window airing are proposed. The models are intended to be a tool for designers and occupants which they can use when they want to know how long a window should be open and how many windows should be opened. Tracer gas experiments have been performed both in a small test room and in classrooms. The specific conditions concerning airing require a special calculation method to determine the air change obtained during the tracer gas measurements. New methods for dealing with this have been proposed. The analytical models have been compared with the measurements. The results show that agreement is quite good and that the models can be used when rough estimates are of interest. The effect window airing has on a mechanical supply and exhaust system has been investigated by calculations with the computer program PFS. It is only when wind velocities are high that airing disturbs the flows in the system. The thesis include two studies concerning mechanical ventilation. A duct system with no means of balancing has been studied by calculation with the program PFS. A number of classrooms are assumed to be located next to each other. It is assumed that the flows to each room are equal and that the branch ducts to each room are equally spaced. The results show that a supply duct system may be designed without balancing. An exhaust duct system however requires balancing if the flows exhausted from the classrooms are to be of the same magnitude. Heat recovery in a ventilation system has also been studied by calculations. The energy need and the total costs including the whole service life have been calculated. It was found that heat recovery pays off even for a rather limited operating time. A sensitivity analysis has shown what factors are of significance when a heat exchanger is designed.
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| 15. |
- Wall, Maria
(författare)
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Climate and Energy Use in Glazed Spaces
- 1996
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Glazed spaces ranging from small glazed verandas to large atrium buildings have become a common feature in architecture. A glazed space is greatly affected by aspects of the outside climate such as insolation and temperature. In the design of such spaces, more sophisticated design tools are therefore required in order to estimate the climate inside the glazed space and the energy requirements for heating and cooling than in the design of ordinary buildings. One object has been to elucidate the relationship between building design and the climate, thermal comfort and energy requirements in different types of glazed spaces. Another object has been to study the effect of the glazed space on energy requirements in adjacent buildings. It has also been the object to develop a simple calculation method for the assessment of temperatures and energy requirements in glazed spaces. The research work has mainly comprised case studies of existing buildings with glazed spaces and energy balance calculations using both the developed steady-state method and a dynamic building energy simulation program. Parameters such as the geometry of the building, type of glazing, orientation, thermal inertia, airtightness, ventilation system and sunshades have been studied. These parameters are of different importance for each specific type of glazed space. In addition, the significance of each of these parameters varies for different types of glazed spaces. The developed calculation method estimates the minimum and mean temperature in glazed spaces and the energy requirements for heating and cooling. The effect of the glazed space on the energy requirements of the surrounding buildings can also be estimated. It is intended that the method should be applied during the preliminary design stage so that the effect which the design of the building will have on climate and energy requirement may be determined. The method may provide an insight into how glazed spaces behave with regard to climate and energy.
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| 16. |
- Wallentén, Petter
(författare)
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Heat Flow in Building Components, Experiment and Analysis
- 1998. - TABK 98/1016
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Three building components exposed to natural climate were studied: a dynamic insulation in the ceiling of a house, an outer wall and one window in the same wall. The term dynamic insulation implies that part of the inlet or exhaust air passes through the insulation of a house. A house with dynamic insulation was continuously measured for approximately a year and a half. The performance of the dynamic insulation was estimated by using hourly values of the temperature distribution inside the insulation. The air flow through the insulation was calculated as the air flow that best matched the measured temperature distribution. For the calculations both the transient and steady state heat transfer equations were used. The dynamic U-value for the insulation was about 0.05 W/m2°C for the ceiling. This corresponds to a dynamic energy efficiency for the insulation of 35%. Taking into account that only 40% of the total supply air passed through the insulation, the total efficiency became 14%. A heat exchanger for ventilation air have an efficiency above 60%. The general conclusion from the measurements was that dynamic insulation requires a house constructed to much higher standards, as far as air leakage is concerned, in order to work properly. An outer ambient wall with a window were studied with both theoretical analyses and measurements performed under conditions with natural climate. The method used was to estimate the heat flow through wall and window from measured temperatures and solar radiation. The longwave radiation was calculated from surface temperatures. The convective heat transfer was calculated as the difference between the heat flow through the building element and the longwave radiation. With the one-dimensional dynamic heat transfer model for the window which included shortwave radiation it was possible to measure the continuous heat flow through a window from temperature sensors and solar radiation measurements. With the one-dimensional finite difference model for the heat transfer through the wall it was possible to calculate the heat flow through a wall from temperature sensors. It was possible to continuously measure the convective heat transfer coefficient on the inner surface of a wall or a window. The accuracy was not very good: at best ±15% for the window and ± 20% for the wall. Even with this low accuracy the effect of different heating and ventilation strategies on the inside could clearly be detected. The results showed that the importance of the ventilation design and the position of the radiator is crucial. Local convective heat transfer coefficients may be more than 10 times the expected, due to ventilation or position of the radiator.
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| 17. |
- Wang, Zhiwu
(författare)
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Controlling Indoor Climate. Passive cooling of residential buildings in hot-humid climates in China
- 1996
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Overheating is a paramount problem in residential buildings in hot-humid climates in China during summer. This study aims to deal with the overheating problem and the problem of poor air quality in dwellings. The main objective is to improve indoor thermal conditions by passive cooling approaches, climatisation techniques in buildings without auxiliary cooling from air conditioning equipment. A field study is carried out in southern China to ascertain the current situation of indoor environment in residential buildings. By literature survey a thermal comfort index SET (Standard Effective Temperature) is selected as a suitable index to evaluate indoor thermal environment in a hot-humid climate. This thesis focuses on the study of cross-ventilation in apartments, which is one of the most effective ways of natural cooling in hot-humid climate, but is also one of the least understood parts in controlling indoor climate. The Computational Fluid Dynamics (CFD) technique is used, which is a new approach, since cross-ventilation studies have been conventionally made by wind tunnel tests. The validations of the CFD technique are examined by a comparison between wind tunnel tests and computer simulations. The factors influencing indoor air movement are investigated for a single room. Cross-ventilation in two apartments is studied, and the air change efficiency in a Chinese kitchen is calculated with CFD techniques. The thermal performance of ventilated roofs, a simple and widely used type of roofs in the region, is specially addressed by means of a full-scale measurement, wind tunnel tests and computer simulations. The full-scale measurement compares thermal performance of ventilated roofs with other types of roofs. The wind tunnel tests examine ventilation behavior of the roofs and computer simulations study the parameters influencing the thermal properties of ventilated roofs. An integrated study of passive cooling approaches and factors affecting indoor thermal comfort is carried out through a case study in a southern Chinese city, Guangzhou. This thesis demonstrates that passive cooling measures have a high potential in significantly improving indoor thermal conditions during summer. This study also gives discussions and conclusions on the evaluation of indoor thermal environment; effects influencing cross-ventilation in appartments; design guidelines for ventilated roofs and an integrated study of passive cooling.
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