Dissertations / Theses on the topic 'Ventilation of work buildings'

xvi, 117 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.
Energy and environmental concerns warrant reconsideration of operable windows as a means of ventilating and cooling office environments. To design for optimal window use and performance, architects must understand human interaction with operable windows and the factors that influence occupant participation in their thermal environment. This thesis examines workers' personal control of operable windows in their office space through the lens of the following attributes: proximity, orientation, and accessibility to operable windows, office floor height, and the operational methods of windows. Three sites in the Minneapolis metro area were examined through site visits, informalinterviews, collection of physical traces, and a questionnaire. Research data reveal that proximity is the greatest determinant of window use. Other attributes have varying degrees of influence on use of windows. Surprisingly, workers valued operable windows significantly more for fresh air than for cooling.
Committee in Charge: Professor John Rowell, Chair; Professor Brook Muller; Professor G.Z. Brown

During renovation Ljusåret 2 was converted to a modern office with an activity based work style (ABW) with a Demand Controlled Volume (DCV) ventilation system connected to a closed-loop duct. Cooling is provided through air handling units and active water based beams, the underfloor heating system was kept. Written instruction and specification have been studied for the two different control systems Schneider EcoStructure and Lindinspect. Both control systems have been analyzed according to time schedule, set-point and process value by using different functions in software. To be able to perform a energy audit and look at indoor climate for Ljusåret 2 there have been studies according to underfloor heating, constructions of ventilation system, diversity factor for DCV, closed-loop-ducts, heat losses from ducts, cooling demand and energy certification. According to this audit, energy performance is calculated to 89.1 kWh/m2 according to building energy, activity energy is not audited or calculated. During design phase, an energy calculation was made by an energy consultant with the result of 81.3 kWh/m2. The estimated performance is a 9.6 % increase. This building is designed for Miljöbyggnad certification of level silver and should be ≤ 109 kWh/m2,year. According to audit and calculation for energy performance this level is possible to keep. The estimated energy performance have been calculated with only 4 month of statistics from January until April 2019 because Ljusåret 2 have just been renovated. District heating has been estimated through the energy signature by data from energy meter. Electrical components for the building have been measured and energy usage calculated. Energy produced by compression chiller have been estimated with calculated performance from design phase and adding heat transfer between rooms and supply ducts. Energy between rooms and supply ducts were not included in energy calculation during the design phase. According to the control system for the DCV system there have been some issues with high temperature in supply ducts even when they are supplied with 15 ºC from air- handling unit. There have been measurement to the ventilation system 5701-5704 that is connected to a close-loop duct with a result of temperatures between 15.2 ºC up to 21.4 ºC and the velocity has varied between 0.05-2.1 m/s in different measurement spots. This is an increase of 6.4 ºC. A heat transfer calculation have been made in Paroc Calculus to estimate heat transfer between room and supply ducts. The results of this calculation indicates the same level of temperature increases as when the system was measured. With no thermal insulation cooling capacity is lost to half after less than 5 m with a velocity of 0.2 m/s, after 15 m with a velocity of 1 m/s and 30 m with a velocity of 2 m/s . This should be compared with supply duct with 20 mm of thermal insulation that has lost its cooling capacity after less than 13 m with a velocity of 0.2 m/s, after 63 m with a velocity of 1 m/s and is increase with 4 ºC after 100 m with a velocity of 2 m/s. Using closed-loop ducts with velocity below 2.0 m/s and without thermal insulation combined with under tempered supply air is not a good combination. Even short length with low velocity and lack of thermal insulation is devastating because of heat transfer according to logarithmical temperature difference between room and supply ducts. A closed-loop duct is often designed as a pressure chamber and recommended when using DCV and/or VAV ventilation to avoid problems with noise and to be able to reduce the need of dampers. Problems with temperature increasing according to velocity in ducts must be taken in consideration. For Ljusåret 2 this will affect district heating usage where ducts are placed because underfloor heating must compensate heat transfer. Chilled water must be provided an extra time for rooms with both DCV and chilled beams and rooms with only DCV is less comfortable which they could been with a correct installation.

Wards occupy significant proportions of hospital floor areas and due to their constant use, represent a worthwhile focus of study. Single-bed wards are specifically of interest owing to the isolation aspect they bring to infection control, including airborne pathogens, but threats posed by airborne pandemics and family-involvement in hospital care means cross-infection is still a potential problem. In its natural mode, ventilation driven by combined wind and buoyancy forces can lead to energy savings and achieve thermal comfort and high air change rates through secure openings. These are advantageous for controlling indoor airborne pathogens and external air and noise pollution. However, there is lack of detailed evidence and guidance is needed to gain optimum performance from available natural ventilation systems. This research is a proof of concept investigation into the feasibility and impact of natural ventilation systems targeting airflow rates, thermal comfort, heating energy and control of pathogenic bio-aerosols in hospital wards. In particular, it provides insights into the optimal areas of vent openings which could satisfy the complex three-pronged criteria of contaminant dilution, low heating energy and acceptable thermal comfort for occupants in a naturally ventilated single bed ward. The main aim of this thesis is the structured study of four systems categorised into three groups: Simple Natural Ventilation (SNV) in which single and dual-openings are used on the same external wall; Advanced Natural Ventilation (ANV) which is an emerging concept; and finally Natural Personalised Ventilation (NPV) which is an entirely new concept borne out of the limitations of previous systems and gaps in literature. The focus of this research is in the exploratory study of the weaknesses and potentials of the four systems, based on multi-criteria performances metrics within three architecturally distinct single-bed ward designs. In contributing to the body of existing knowledge, this thesis provides a better understanding of the performances of three existing systems while presenting the new NPV system. The analysis is based on dynamic thermal modelling and computational fluid dynamics and in the case of the NPV system, salt-bath experiments for validation and visualisation of transient flows. In all cases, wards were assumed to be free of mechanical ventilation systems that might influence the natural flow of air. The thesis meets three major objectives which have resulted in the following contributions to current knowledge: An understanding of the limitations and potentials of same-side openings, especially why and how dual-openings can be useful when retrofitted into existing wards. Detailed analysis of bulk airflow, thermal comfort, heating energy and room air distribution achievable from existing SNV and ANV systems, including insights to acceptable trickle ventilation rates, which will be particular useful in meeting minimum dilution and energy requirements in winter. This also includes qualitative predictions of the airflow pattern and direction obtainable from both systems. The innovation and study of a new natural ventilation system called Natural Personalised Ventilation (NPV) which provides fresh air directly over a patient s bed, creating a mixing regime in the space and evaluation of its comfort and energy performances. A low-energy solution for airborne infection control in clinical spaces is demonstrated by achieving buoyancy-driven mixing ventilation via the NPV system, and a derivative called ceiling-based natural ventilation (CBNV) is shown. A comparative analysis of four unique natural ventilation strategies including their performance rankings for airflow rates, thermal comfort, energy consumption and contaminant dilution or removal using an existing single-bed ward design as case study. Development of design and operational recommendations for future guidelines on utilising natural ventilation in single-bed wards either for refurbishment or for proposed designs. These contributions can be extended to other clinical and non-clinical spaces which are suitable to be naturally ventilated including treatment rooms, office spaces and waiting areas. The findings signify that natural ventilation is not only feasible for ward spaces but that there is opportunity for innovation in its application through further research. Future work could focus on related aspects like: impacts of fan-assisted ventilation for a hybrid flow regime; pre-heating of supply air; integration with passive heat recovery systems as well the use of full-scale experiments to fine-tune and validate findings.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 192-195).
Natural ventilation in buildings has the potential to reduce the energy consumption usually associated with mechanical cooling while maintaining thermal comfort and air quality. It is important to know how building parameters, in particular its thermal mass properties and heat loads incurred, affect a building's transient thermal response to incoming outdoor air. A proper ventilation schedule is also needed to make optimal use of the free direct or night cooling. To investigate these factors, a first principles heat transfer energy model is developed to numerically simulate in MATLAB the air temperature profile of a single-zone cross-ventilated room. The physics behind natural ventilation at building level is also investigated using multi-zone modeling, as done in CoolVent, an existing MIT airflow modeling tool. In the process, the simulation capabilities of MIT Design Advisor, an existing building energy simulation tool, are expanded upon from shoe-box to interconnected multi-zone modeling. Optimal natural ventilation scheduling, with a view to maximizing thermal comfort, is then studied using two optimization techniques: dynamic programming and global search optimization, using the simple room energy model as the simulation engine. In the process, an algorithm framework is developed to optimize the ventilation scheduling on a rolling day-horizon basis based on input weather data and occupancy schedule. The use of rule-based control, as opposed to the aforementioned model-optimized control, is also explored due to its ease of implementation in building automation software. The former form of control is found to maintain comparable thermal comfort when separate rules for specific scenarios, such as night-overcooling or day-overheating, are gathered together to constrain the room air temperature. It is however critical to identify and calculate proper set-points for these rules.
by Karine Ip Kiun Chong.
S.M.

In the present climate of energy conservation and CO2 emission consciousness, building heating, ventilating and air conditioning (HVAC) systems are required to achieve thermal comfort and indoor air quality in the most energy efficient manner possible. To this end optimising the use of natural ventilation is considered an area which can significantly reduce both the occupants discomfort and the energy consumption. The ability to effectively control the indoor environment would considerably enhance the use of natural ventilation. The overall aim of this research is to develop, commission and evaluate a fuzzy rule-based controller which can vary the resistance of ventilation opening in order to maintain an acceptable comfort conditions in the occupied space. The design of the fuzzy control system starts by establishing certain quantization levels for the input/output variables along with corresponding membership functions. Aspects of input and output variable choice together with their linguistic labels are explained and presented. Control rules are defined based on the off-line thermal modelling, experimental results and through discussions with experts. A dynamic air flow distribution is investigated through a series of experiments for different environmental conditions and opening levels without any control action. Three rule-bases of different complexity are developed and presented. All solutions are simulated in an input-output space and their differences presented in more detail through examples of the Mamdani inference method application. Controller validation is initially carried out using simulation as this offers the possibility of testing controllers under extreme conditions regardless of test room physical limitations. Simulations are carefully designed to allow simultaneous comparison of different controllers' performances. Then on-line validation is carried out in the test room by measuring the air flow distribution with and without the controller in action. A naturally ventilated test room and its instrumentation is set up. A controller commissioning methodology is established, involving the choice of software and hardware platforms and data acquisition methodology.

This thesis, “Natural Ventilation in Buildings -Architectural concepts, consequences and possibilities”, is the result of a PhD study financed by Hydro Aluminium/Wicona, The Research Council of Norway and the Norwegian University of Science and Technology (NTNU). The work was carried out at the Department of Architectural Design, History and Technology, Faculty of Architecture and Fine Art at NTNU in the period January 2000 to March 2003.

The study has been conducted in close collaboration with fellow researchers Bjørn J. Wachenfeldt and Tor Arvid Vik. Chapter 2 “Principles and elements of natural ventilation” is in its entirety written by the three of us together.

The main objectives of this work have been to identify and investigate the architectural consequences and possibilities of natural ventilation in office and school buildings in Northern Europe. Case studies and interviews with architects and HVAC consultants have been the most central “research instruments” in achieving this. Three buildings have been studied in detail. These are the GSW Headquarters in Germany, the B&O Headquarters in Denmark, and the Mediå Primary School in Norway. In addition, a larger set of buildings has been used to substantiate the findings.

The most important findings of this work are that:

- utilisation of natural ventilation in buildings has architectural consequences as well as possibilities.

- natural ventilation primarily affects the facades, the roof/silhouette and the layout and organisation of the interior spaces.

- the ventilation principle applied (single-sided, cross- or stack ventilation) together with the nature of the supply and extract paths, i.e. whether they are local or central, are of key importance for the architectural consequences and possibilities.

- designing a naturally ventilated building is more difficult than designing a similar but mechanically ventilated building. An interdisciplinary approach from the initial stages of design is mandatory for achieving successful natural ventilation concepts.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Architecture, 2001.
"June 2001."
Includes bibliographical references (p. 171-172).
In the United States, many of the commercial buildings built in the last few decades are completely mechanically air conditioned, without the capability to use natural ventilation. This habit has occurred in building designs since the designers do not have the tools to understand the impact of using natural ventilation as an option in conditioning a building. Research has been conducted to create a better understanding of how natural ventilation can be used successfully in building designs. First, understanding the buildings that currently use natural ventilation and secondly by analyzing how buildings can operate in different climates. It is important in the building design industry to know the feasibility of designs, and is therefore important to see buildings that have used natural ventilation techniques. It is also important in the building design industry to know if the natural ventilation techniques that have been used, can be used in the climate that a building needs to be designed for. It was determined that increased airflow through natural means can significantly enhance the functionality of buildings in the United States. Throughout the United States there are numerous hours when outdoor conditions suggest using natural ventilation for a primary cooling system. Natural ventilation can help a building maintain comfort for the occupants, reduce energy usage, reduce cooling equipment size and increase indoor air quality. With the use of a natural ventilation design tool, designers can understand the impact that each of the buildings major features has on the overall comfort or energy required to make it comfortable.
by Brian N. Dean.
S.M.

Energy usage in buildings has become a major topic of research in the past decade, driven by the increased cost of energy. Designing buildings to use less energy has become more important, and the ability to analyze buildings before construction can save money in design changes. Computational fluid dynamics (CFD) has been explored as a means of analyzing energy usage and thermal comfort in buildings. Existing research has been focused on simple buildings without much application to real buildings. The current study attempts to expand the research to entire buildings by modeling two existing buildings designed for energy efficient heating and cooling. The first is the Viipuri Municipal Library (Russia) and the second is the Margaret Esherick House (PA). The commercial code FLUENT is used to perform simulations to study the effect of varying atmospheric conditions and configurations of openings. Three heating simulations for the library showed only small difference in results with atmospheric condition or configuration changes. A colder atmospheric temperature led to colder temperatures in parts of the building. Moving the inlet only slightly changed the temperatures in parts of the building. The cooling simulations for the library had more drastic changes in the openings. All three cases showed the building cooled quickly, but the velocity in the building was above recommended ranges given by ASHRAE Standard 55. Two cooling simulations on the Esherick house differed only by the addition of a solar heat load. The case with the solar heat load showed slightly higher temperatures and less mixing within the house. The final simulation modeled a fire in two fireplaces in the house and showed stratified air with large temperature gradients.
Master of Science

Determining optimum building orientation for naturally ventilated buildings is an important concept. Obtaining the optimum orientation will determine the success of the performance of a naturally ventilated building.
This project deals with obtaining the preferred building orientation for 10 regional weather stations across the province of Ontario. Different methods were utilized to obtain the preferred building orientation: the average ventilation rate method, the percentage of ventilation rates above and below the minimum summer ventilation rates, and the consecutive hours method, ie. the number of weather events that are below the minimum summer design ventilation rate for a specific building configuration. The analysis involves six building orientations (0$ sp circ$, 30$ sp circ$, 60$ sp circ$, 90$ sp circ$, 120$ sp circ$, and 150$ sp circ$) with respect to North, and exterior temperatures greater than or equal to 20$ sp circ$C, 25$ sp circ$C, or 30$ sp circ$C.
Optimizing building orientation, to minimize the number of weather events where the ventilation rates are below the summer design ventilation rate is the general goal of this research work.
A statistical analysis was carried out based on the results obtained from the data for the frequency of ventilation rates versus the ventilation rates below the summer design ventilation rate, for all 10 Ontario weather stations, for temperatures greater than or equal to 20$ sp circ$C, and all six building orientations. The output of the statistical analysis showed that for the above mentioned temperature range, that there is a relationship between the ventilation rates below the design summer ventilation rate and building orientation.

Modern development in many Third World countries in the hot regions of the world,, have been accompanied by the construction of highly energy-wasteful buildings. The interiors of these buildings have to be mechanically airconditioned in order to achieve thermal-comfort conditions. The consequence of this, has been the rapid increase in electricity-generating plant capacity to match demand (of which, for example at present in Oman, more than 70% nationally is used for air-conditioning modern, energyinefficient buildings). The aim of this work was to find the most suitable way of stabilising or even reducing the electricity demand in a country like Oman. The first step taken to achieve this aim, was to study and draw out lessons from the vernacular architecture of the different climatic regions in Oman. This has been followed by a literature survey that looks at passive and active natural cooling techniques for buildings in hot climates. Mathematical models were then developed to analyze and compare those passive techniques that are most suitable for an environment like that of Oman. Different ways of reducing the heat gain through the roof were investigated and compared. These include the addition of insulation, shading, air-cooling of the roof when the ambient air temperature is lower than that of the roof, and roof ponds. Roof ponds were found to be the most effective of those techniques analyzed. An improved design of the roof pond (the Water Diode roof pond) that eliminates the need for covering the roof pond during the day and uncovering it at night, was suggested and analyzed. The analysis showed promising results. Mathematical models were also developed to analyze and compare dif f erent ways of reducing the heat gain through the walls. These included the use of closed cavities, naturally ventilated cavities, the addition of insulation, and the effect of using brick as compared to concrete block. The analysis suggested that the combination of a Water Diode roof pond and insulated brick wall construction will reduce the heat gain through the envelope of a single room by more than 90%, when compared to a room with un-insulated roof and single-leaf concrete block walls. An empirical validation of the mathematical models was conducted. The results showed a good agreement between the actual and predicted values. An economical analysis of the commonly used roof and wall constructions in Oman, was also conducted. This compared the life-cycle cost of nine different construction techniques, with eight different airconditioning schedules. The result of this analysis showed a clear advantage of using roof insulation, reflective double glazing, and insulated walls with brick outer-leaf and concrete block inner-leaf.

This study investigated the effectiveness of wind-driven natural ventilation in courtyard and atrium-type buildings, particularly in the context of ventilative cooling. Courtyard and atrium buildings are currently enjoying great popularity. Perhaps a primary reason for their revival comes from the energy and environmental awareness of the current period, in which courtyard and atrium concepts are emerging as very promising. Wind-driven ventilation is one of the most basic and probably among the most efficient ways to prevent overheating, and provide cooling in the summer season, especially in humid climates. A review of previous works showed that little attention has been given to the wind-driven natural ventilation capability of these structures, and to the means of maximizing this ventilation. This study was thus aimed to fill part of the gap in this subject. In order to evaluate the wind-driven ventilation effectiveness of these structures, and to examine some of the influential parameters, experimental wind tunnel tests were made. Actual indoor air flows were measured in small replica models of four-storey courtyard and atrium buildings by means of small calibrated orifice plates. A parametric study of the geometry of the courtyard was made in isolation conditions, where the depth and breadth of the courtyard were systematically varied. Several atrium ventilation modes were tested both in isolation and in urban terrains. The tests involved different roof geometries and various roof porosities. The measurements were followed by a discussion on the validity of simple computational methods to predict airflow in atria. The investigation portrayed the importance of some factors, such as the wind orientation rather than the courtyard geometry, for enhancing the flow in these structures. The superiority of some atrium designs over the courtyard types, particularly in sheltered sites, was underlined. The study concluded with a discussion of design guide-lines and referred the reader to an application as an example, describing a simple step-by-step method to estimate the cooling benefits of these structures in a particular site, and making use of the measurement data obtained from the study.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Architecture, 2002.
Includes bibliographical references (p. 186-194).
With the discovery of many economic, environmental, and health problems in sealed and mechanically ventilated buildings, the concept of natural ventilation has been revived. "Buildings that breathe" have become more and more desired by ordinary people and architects. Although natural ventilation is conceptually simple, it is difficult to design and control. At present, methods to study natural ventilation are either inaccurate or costly. This study aims at solving these problems by using large eddy simulation (LES). In LES, a three-dimensional, time-dependent method, the contribution of the large, energy-carrying structures is computed directly and only the smallest scales of turbulence are modeled. This investigation has identified a filtered dynamic subgrid-scale model of LES to study natural ventilation. The experimental data from a wind tunnel, a full-scale test chamber, and other research data have been used to validate the LES program. Methods have been developed to solve the problems encountered in validating LES models for natural ventilation studies. Studying the characteristics of different indoor and outdoor airflows helps to identify the best SGS model for those flows. By comparing the results of using large and small computational domains, an appropriate domain size is recommended to save computing time. It is also found that simulating the transient properties of incoming wind, such as the principal frequency of the turbulent fluctuations, influences the pressure distributions around buildings.
(cont.) The mechanism of natural ventilation is investigated using the numerical and experimental results. The fundamental impact of turbulence characteristics on ventilation rate is discussed and a new definition to calculate the ventilation rate is introduced. The distributions of velocities, pressures, temperature and energy spectra, and the computed ventilation rates, suggest that natural ventilation performance is significantly affected by thermal conditions and geometry of a building. LES provides the best tool to predict the effects under those conditions. Finally, with the implementation of a Lagrangian particle model, LES is applied to compute particle dispersion in buildings, which provides valuable information to improve indoor air quality. Good results were found for particles larger than 10 micrometers. Further work is needed for smaller particles.
by Yi Jiang.
Ph.D.

During the summer, buildings in hot dry climates have the inevitable problem of cooling. These climates are characterized by hot summer days with cold nights, a high degree of solar radiation, low humidity and with a nearly fixed seasonal and daily pattern of wind. These natural phenomena could be exploited by nocturnal ventilation to cool the building fabric, thus saving energy during the day and providing comfort at night. The procedures to evaluate thermal performance of buildings with special reference to nocturnal ventilation are studied. Various approaches to building thermal response are first reviewed. Dynamic thermal simulation computer models are developed to predict hourly 'internal temperatures'. These are used to study the various constituents of models. They are based on: -the Admittance Method (as suggested by the CIBSE Guide); -a similar procedure but with higher harmonics; -the Response Factor Method (suggested by ASHRAE); -and the Finite Difference Method. A room surrounded by similar rooms in a multi-storey building, having only one external wall, was simulated in the laboratory. It was subjected to typical variations of a hot climate. Predictions of the computer simulations are compared with laboratory results and it is shown that -the closest agreement was obtained with the Response Factor and Finite Difference methods which are equally good; -for higher rates of ventilation, representation of a room by a simple three nodes model thermal network will give sufficiently accurate results; while for lower rates of ventilation a more detailed model gives more accurate results; -the standard Admittance Method gives adequate results, especially with higher rates of ventilation. It could also be used for hourly temperature-, calculations and variable ventilation without loosing significant accuracy; -a fuller treatment in the Admittance Method of time-lag and time-lead, associated with the dynamic thermal factors, will not greatly improve the results. An increase in the number of harmonics in the procedure did not also result in significant improvements, especially with a high rate of ventilation. Natural ventilation into rooms through open windows in these climates is theoretically investigated. It is shown that the rate of natural air flow obtained may be sufficient to meet the requirements of passive cooling by nocturnal ventilation. A computer program is developed to calculate the rate of air flow in multi-zone buildings, and a new relationship is suggested, which will reduce the complexity of natural air flow calculations in multi-zone buildings subjected to cross ventilation.

Natural ventilation is a low-energy design strategy that has the potential both to significantly reduce energy usage in buildings and to provide a healthy and comfortable indoor environment. It has particular potential for use in tall, multi-storey buildings. However, the integration of natural ventilation into these large building designs has seen mixed success. Furthermore, there is a gap between simple 'rule-of-thumb' design guidance and detailed, computational design tools. This research attempts to bridge the gap between the simple and detailed with the broad aim of providing rapid and intuitive guidance for use in preliminary design. We use a simple mathematical approach to develop a coherent and easy-to-use framework for modelling ventilating flows, which quantifies the interactions between a core set of design variables. We focus in particular on buoyancy-driven ventilation in buildings with atria, ventilation stacks and/or similar vertical spaces that span multiple floors. Simple methods centred around hand calculations and design charts are developed to inform the sizing of vents in an 'ideal design' scenario, in which the desired ventilation flow rates and air temperatures are delivered to all occupants within a building. We define a measure of the ventilation performance of an atrium and use this to provide an indication of when an atrium is beneficial to a ventilation system design and when it is detrimental. We also use a transient flow analysis to consider 'off-design' scenarios, in which undesirable flow regimes may occur, and to place design tolerances on the building envelope. It is hoped that this work will form a point of reference for further research and for future revisions of design guidance literature.

Sectoral energy consumption analyses clearly indicate that building sector plays a key role in global energy consumption, which is almost 40% in developed countries. Among the building services; conventional heating, ventilation and air conditioning (HVAC) systems have the greatest percentage in total energy consumption of buildings. According to the latest research, HVAC is responsible for around 40% of total building energy consumption and 16% of total global energy consumption. In this respect, decisive measures need to be taken to mitigate the energy consumption due to HVAC. The research carried out within the scope of this thesis covers innovative heating, cooling and ventilation technologies for low-carbon buildings. The novel technologies developed are introduced and investigated both theoretically and experimentally. The results indicate that optimised HVAC systems with waste heat recovery have a significant potential to mitigate energy consumed in buildings, thus to halt carbon emissions. Especially plate-type roof waste heat recovery units are very attractive for the said hybrid applications with a thermal efficiency greater than 88%. The said systems are also promising in terms of overall coefficient of performance (COP). The average COP of plate-type roof waste heat recovery unit is determined to be about 4.5, which is incomparable with those of conventional ventilation systems. Preheating performance of fresh air in winter season is found to be remarkable. Comprehensive in- situ tests clearly reveal that the temperature rise in fresh air is found to be around 7 °C. Plate-type roof waste heat recovery units also provide thermal comfort conditions for occupants. Indoor CCE concentration is observed to be varying from 350 to 400 ppm which is very appropriate in term of air quality. In addition, average relative humidity is found to be 57%, which is in the desired range according to the latest building standards. Desiccant-based evaporative cooling systems are capable of providing Abstract desired indoor environments for occupants as well as having considerably high COP ranges. An average of 5.3 °C reduction is achieved in supply air temperature by utilising those systems as well as having relative humidity distribution in thermal comfort range. The dehumidification effectiveness is found to be 63.7%, which is desirable and promising. The desiccant-based evaporative cooling system has a great potential to mitigate cooling demand of buildings not only in hot arid but also in temperate humid climates.

This work describes result from both measurements on anumber of one family houses, an analytical study of a one-zonemodel and multi zone studies of a two storey building. Thesimulations are performed as both parametric studies, withcombined values of outside temperature, wind velocity and winddirection, and whole year simulations. For the latter, aclimate file for the northern Swedish city Östersund isused.

The results, for the whole year simulations, are presentedas ventilation availabilities. The ventilation availability isdefined as the relative time of the heating season during whicha specified airflow is exceeded. This specified airflow maye.g. be a Building Code requirement if such exists.

The influence of different measures, and combinations ofmeasures, on the ventilation availability has been determinedfor the different rooms. It is found that acceptableventilation availability is possibly to achieve with naturalventilation. However, it requires large supply and overflowopenings and extended ventilation chimneys. These chimneys maybe difficult to accept from an esthetical point of view. Thenatural system is also very sensitive for changes in winddirection.

To ensure required airflows at all times, an exhaust orhybrid ventilation system may be necessary.

Some recommendations may be based on this study.

-Consider the predominating wind direction. It’san advantage to have more supply openings on the leeward side,i.e. to place“humid”rooms towards the knownwindward side.-Use different chimney heights from the different“humid”rooms, to balance the internal airflows. Ifmechanical exhaust is used, it may be used only from some ofthe“humid”rooms, preferable the ones with closeddoors.-Use as large supply and overflow openings aspossible. Different opening areas may be used to balance theairflows, especially if the predominating wind direction isknown. Acoustic problems may be a limiting factor for theopening area. There may also exist a maximum opening area abovewhich stability problems occur.-Construct ventilation chimneys and chimney outlets ina way, that the windgenerated pressure at the outlet is alwaysnegative and independent of wind direction. Insulate thechimneys to avoid cooling of the air and decreased buoyancyforces.

-Use different chimney heights from the different“humid”rooms, to balance the internal airflows. Ifmechanical exhaust is used, it may be used only from some ofthe“humid”rooms, preferable the ones with closeddoors.

-Use as large supply and overflow openings aspossible. Different opening areas may be used to balance theairflows, especially if the predominating wind direction isknown. Acoustic problems may be a limiting factor for theopening area. There may also exist a maximum opening area abovewhich stability problems occur.

-Construct ventilation chimneys and chimney outlets ina way, that the windgenerated pressure at the outlet is alwaysnegative and independent of wind direction. Insulate thechimneys to avoid cooling of the air and decreased buoyancyforces.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Architecture, 2005.
Includes bibliographical references (p. 136-139).
Our growing understanding of technology and environment has expanded the complexities of producing large naturally ventilated buildings. While it may be argued that designing for natural ventilation is a straightforward, intuitive process, somewhere between the simple diagrams and signing off on the building, the designer must be able to verify that the design will be effective -- essentially that people will be comfortable, and that the system is robust. Today, professional experience is the only methodology to understand the broad considerations behind these new structures. Literature reviews and interviews with industry professional illustrate the lack of information available to the academic and practicing audiences describing the series of calculated decisions and challenges surrounding the design of large naturally ventilated buildings. Architecture professionals and students desiring to engage in these recent, innovative practices would therefore benefit from a resource describing the options available to evaluate a proposed design and optimize a completed building. The thesis examines the strategic decisions in evaluation and monitoring of three case study buildings (Morphosis' San Francisco Federal building, Fosters & Partners' Swiss Re building, and Behnisch & Behnisch's Genzyme building) and derives principles influencing future architecture practice.
by Wendy Meguro.
S.M.

Ventilation is essential if an adequate environment in buildings is to be provided. Natural ventilation is a sustainable method commonly used to achieve this. Natural ventilation can occur from random flow of air through unintentional (adventitious) openings, commonly referred to as infiltration, or can be facilitated through purpose-provided openings - commonly called controlled natural ventilation. Stringent national and international regulations have led to building structures becoming more and more air-tight so that ventilation is confined to airflow through intentionally provided openings only. These purpose-provided openings typically consist of one or a combination of basic components such as louvers, insect-screens or noise baffles. An extensive literature review indicated that the airflow performance of combinations of such components has neither been thoroughly determined nor fully understood, making it difficult to accurately predict their building performance. This investigation set out to answer some of these questions by employing experimental and computational fluid dynamics (CFD) parametric studies. For the experimental study, a test rig was designed and constructed in accordance with European Standard BS EN 13141-1: 2004. The text rig was designed with sufficient flexibility to enable individual components and combinations of various components to be investigated. Components tested ranged from ordinary slots fabricated from pine wood to commercial ventilators and mesh-screens as are commonly found in natural ventilation applications. The results of this investigation indicate that the overall airflow properties of a ventilator are influenced by the combination of constituent components, the manner in which the components are incorporated into a ventilator and also the direction of airflow through it. A CFD study utilising three-dimensional models of some of the components tested during the experimental phase, and employing the k - ? turbulence representation was facilitated by a commercial software package (FLOVENT). Comparisons between CFD results and experimental data were reasonable and acceptable. A new mathematical approach, based up on experimental results, to analyse the airflow properties of combinations of ventilator components is introduced in this thesis. The proposed equations enable relative assessments of the impacts of each component on the overall airflow performance of a ventilator to be made. Comparisons between results from the proposed equations and those obtained experimentally showed good agreement. Although more work could be done to understand the physical meaning of the equations proposed, the author believes that this investigation has set a foundation for a generic representation of ventilator airflow performance. As such, refinements to the proposed equations would inevitably result if further research into this task is undertaken.

Thermal energy storage (TES) including phase change materials (PCMs), is an important technology to provide free cooling and ventilation in buildings. They have potential advantages over mechanical ventilation systems in terms of energy requirements, economic and environmental benefits. The main aim of this research is to study an air-multiple PCMs unit for the free cooling and ventilation applications relying on the daytime and night-time temperature difference during the summer. The research work carried out and reported in this thesis includes an extensive literature review on TES, incorporating PCMs, experimental investigation of the parameters influencing the charging and discharging time and the air outlet temperature of an air-PCM unit. It has been observed that the heating/cooling rate of PCM is important factor in studying charging/discharging behaviour of a PCM. For this, the determination of the thermophysical properties of the selected PCMs by Differential Scanning Calorimetry (DSC) is carried out. Similar heating rate, as per experimental testing, established better validation results when used in CFD model. The CFD model aims to predict the outlet air temperatures and the PCM temperatures for validation of the experimental data. Further on, parametric study will use the verified CFD model of an air-multiple PCM unit to identify significant parameters affecting the air outlet temperature, the cooling time and the PCM charging time. Finally, this thesis will investigate the potential of an air-multiple PCM unit for free cooling and ventilation of an office building under Portuguese climatic conditions through a CFD model. The experimental study has shown that the air inlet temperature and velocity play a major role on the PCM charging/discharging time and on the air outlet temperature. The numerical and experimental studies show that the developed CFD model has the ability to give good agreement for the prediction of the PCM charging and discharging times and the air outlet temperature with experimental results. Based on the experimental work and numerical analysis, an air-multiple PCM unit is proposed with a cooling load of 1.02 kW for office building. This allowed the reduction of the initial capital cost, the maintenance cost and the environmental benefits when compared to a traditional air conditioning unit.

The aim of this thesis is to study the energy performance of a building integrated heating and cooling system. The research objectives are to investigate the system operating characters, to develop mathematical models for the heating and cooling systems, to demonstrate the technologies experimentally, to identify the best designs for a combined system and to investigate the cost effectiveness of the system. The main components of the systems are the aluminium plate façade and the building wall behind it, these form a plenum between them and the air is then heated or cooled as it flows through this plenum. Mathematical models were developed based on the energy balance equations and solved by matrix inversion method. These models were then validated with experimental results. The experiments were carried out in the laboratory with a facade area of 2m2. Two designs of facade were tested, i.e. flat and transpired plates. Results showed that the transpired design gave better thermal performance; the system efficiency for the flat plate was only about 30%, whereas it was about 85% for the transpired plate. On the other hand, a cooling system with double plenums was found to be better than a single plenum. Thus, a transpired plate with two plenums was identified as the best design for space heating and cooling. The cooling efficiency was nearly 2.0 even at low solar radiation intensity. A simulation study was carried out by assuming a 40m2 of façade was installed on an office building in London. The yearly energy saving was estimated as 10,877kWh, which is equivalent to 5,874kgCO2/year of emission avoidance. The system is calculated to cost about £70/m2, and for a discount rate of 5% and 30 years of lifetime, the payback period for this system would be less than a years.

A wooden, perforated, uniform cross-section duct was examined to determine the optimum levels of aperture ratio and fan speed with respect to uniformity of discharge. The optimum aperture ratio for the 8.54 m long duct was 1.0 with a uniformity coefficient of 90.28%. The fan speed had little effect on the uniformity of discharge. The friction factor was experimentally determined to be 0.048 for a non-perforated duct and this value was assumed to be the same for a perforated duct of similar construction. A kinetic energy correction factor was used to analyze the flow in the duct. Values for this correction factor were determined from experimental data. Values of the coefficient of discharge and the total duct energy were calculated. A mathematical model was proposed based on the conservation of momentum and the Bernoulli's equation. The model responded favourably and predicted the duct velocity nearly perfectly and slightly underestimated the total duct energy.

This study aims to investigate the effects of ventilation rate, indoor air temperature, humidity and using a heat recovery ventilation system on indoor radon concentration and distribution. Methods employed include energy dynamic and computational fluid dynamics simulation, experimental measurement and analytical investigations. Experimental investigations primarily utilize a continuous radon meter and a detached house equipped with a recovery heat exchanger unit. The results of the dynamic simulation show that the heat recovery unit is cost-effective for the cold Swedish climate and an energy saving of about 30 kWh per  floor area per year is possible, while it can be also used to lower radon level. The numerical results showed that ventilation rate and ventilation location have significant impacts on both radon content and distribution, whereas indoor air temperature only has a small effect on radon level and distribution and humidity has no impact on radon level but has a small impact on its distribution.

Natural ventilation is a rewarding technique for use in sustainable building design, due to its strengths in health, comfort, energy saving and economy. The speed-up of global warming and urbanisation urges us to effectively utilise this technique in the urban environment. By coupling the virtual wind tunnel and airflow network models, the potential of natural ventilation driven by the combination of wind and buoyancy forces was calculated.

L'humidité relative de l'air est un des paramètres les plus importants ayant une influence sur le confort, la qualité de l'air intérieur et aussi sur la performance énergétique et la durabilité des enveloppes. Les matériaux qui adsorbent et désorbent l’humidité peuvent être utilisés pour modérer l’amplitude des variations de l’humidité relative et ainsi améliorer le climat intérieur et diminuer les consommations énergétiques. Le transfert de masse dans les matériaux hygroscopiques, même si il est pris dans les simulations dynamiques des bâtiments, il est simplifié. Négliger le transport de vapeur d'eau entre l'air et le matériel, ou appliquer des simplifications peut entraîner de graves erreurs dans l'estimation de l'humidité de l'air. L’objectif de ce travail de thèse est d’examiner les paramètres influençant l’échange hygrique entre l’air intérieur et les matériaux de construction dans des conditions normales d’utilisation. Ce travail a été divisé en deux parties : expérimentale et numérique. Comme les propriétés hygrique des matériaux ont un impact important sur les transferts de masse, des mesures détaillées de la perméabilité à la vapeur et de l’isotherme de sorption ont été effectué. Aussi les coefficients convectifs de transfert de masse ont été mesurés. Le critère d’absorption de masse a montré que le taux de celui-ci ne dépend pas seulement du matériel et des revêtements, mais aussi de la température et le mouvement d’air intérieure. L’expérimentation sur l’évaporation de l’eau sur la surface libre d’un liquide a montré que le coefficient convectif de transfert de masse dépend du potentiel de transfert. Il a été présenté que pour les petites différences dans le taux d'humidité relative, le coefficient de transport est plus petit. Les mesures du coefficient convectif de transfert de masse à partir d'un matériau mince hygroscopique ont montré que la valeur du coefficient ne dépend pas seulement de la différence dans le potentiel de transfert, mais aussi du niveau de potentiel. Pour la même différence, les coefficients convectifs de transfert ont des valeurs inférieures pour des faibles niveaux d'humidité relative. Il a également été montré que le coefficient convectif de transfert de masse a des valeurs inférieures pour les échantillons en position verticale que dans la position horizontale. Dans la dernière partie de cette thèse, un nouveau modèle numérique Humi-mur, pour les simulations du flux massique échangé entre l’air et le matériau a été développé et présenté. Le modèle permet une représentation précise des propriétés hygriques : la perméabilité à la vapeur d’eau et l’isotherme de sorption. L’aspect pratique du modèle l'Humi-mur a été présenté. Les résultats montrent que le tampon d'humidité dans les matériaux peut améliorer la perception de la qualité de l'air et empêcher la croissance microbiologique à la surface de l'enveloppe du bâtiment. Il a également été souligné que négliger les effets d'hystérésis de sorption sur les flux d'humidité peut entraîner de graves erreurs dans les calculs
The aim of this thesis was to study the mass exchange between indoor air and material. The influence of several factors on moisture transfer has been verified. Also the convective mass transfer dependency on the relative humidity condition and position of the material has been checked. Finally, a new module with the sorption hysteresis model, Humi-mur, for calculations of mass flow exchanged between indoor air and material has been developed, validated and integrated into the whole building simulation tool TRNSYS. This powerful tool was used to simulate a realistic room under real climatic conditions. The tests on mass uptake have shown that the rate of mass uptake depends not only on the material and coatings but also, some relationships between mass flux and air movement and temperature have been found. The experiment on water evaporation from a free liquid surface showed that the convective mass transfer coefficient depends on the driving potential value. It was presented that for the smaller difference in the relative humidity the transport coefficient is smaller. The measurements of the convective mass transfer coefficient from a thin hygroscopic material showed that the value of the coefficient depends not only on the difference in the driving potential but also on the level of the driving potential. For the same difference the convective transport coefficient has lower values for a lower level of relative humidity. It was also shown that the convective mass transfer coefficient has lower values for samples in a vertical position than in a horizontal position. Finally, the practical use of the Humi-mur model has been presented. The results show that moisture buffering materials can improve perceived indoor air quality and prevent microbiological growth at the surface of the building envelope. It was also pointed out that neglecting the effect of sorption hysteresis on moisture flux can lead to errors in calculations

In many dry desert climates such as in Kuwait, the summer season is long with a mean daily maximum temperature of 45°C. A round 80% of total electricity generation is consumed by air-conditioning systems in domestic buildings. A hybrid cooling technique to reduce the domestic cooling demand would have both environmental and economic benefits for Kuwait. A passive cooling technique, which assists the situation, is ground cooling. In this thesis a thermal model of an earth air heat exchanger (EAHE) has been developed to calculate the pre-cooling of ventilation air that can be achieved for a building through use of a buried pipe below ground surface.

This study develops a decision-support framework assisting the design of non-residential buildings with natural ventilation. The framework is composed of decision modules with input, analysis algorithms and output of natural ventilation design. The framework covers ventilation with natural driving force and mechanical-assisted ventilation. The framework has two major assessment levels: feasibility assessment and comparison of alternative natural ventilation approaches. The feasibility assessment modules assess the potential of the site with the design proposition for natural ventilation in terms of wind, temperature, humidity, noise and pollution conditions. All of the possible natural ventilation approaches and system designs are assessed by first applying constraints functions to each of the alternatives. Then the comparison of alternative approaches to natural ventilation continues by assessing the critical performance mandates that include energy savings, thermal comfort, acoustic control, indoor air quality and cost. Approaches are finally ranked based on their performance.
Ph. D.

Through the last decades, building designers should deal with reliable design strategies to take advantage of natural resources in order to increase energy efficiency in buildings, as well as to promote sustainable development and add value to the society. This thesis proposes a reliable building design strategy to improve buildings energy efficiency by means of natural ventilation (NV) use. The strategy consists in evaluating the most suitable architectural solution in a particular case study taking into account environmental conditions and building surroundings in order to maximize NV use since the early building design stage. Computational fluid dynamics (CFD) techniques are used to conduct the research. This is a powerful design tool that permits buildings NV behaviour simulation prior to building construction. Therefore, the aim of the thesis is to provide a real case study building in which the NV design strategy is applied to show a reliable example and support building design decisions since the design stage. The design strategy is based on the use of a commercial numerical code that solves the fluid mechanic equations. The CFD software simulates the features that influence NV and predicts its behaviour in the different building configurations prior to building construction. This numerical technique allows, on the one hand, the visualization of air flow paths in buildings. On the other hand, many quantifiable parameters are calculated by the software. Through the analysis and comparison of those parameters, the best architectural solutions are chosen. With regards to all possible architectural decisions, the research is focused on the façade configuration selection and the building location. First of all, the NV design strategy feasibility is analysed in a particular region: the Mediterranean Valencian Coastal area (Spain). The region is characterized by the uniform conditions of the prevailing wind during the warm season. Then, a validated CFD simulation is used to analyse qualitatively and quantitatively the building surrounding influence on wind paths through and around buildings. The objective is to compare different façade opening positions and select the alternative that takes more profit of the NV resources available. Additionally, a general quantification of the ventilated façade contribution to buildings energy efficiency is presented under the frame of the façade configuration selection. Secondly, two simulations are conducted to analyse two different building locations. The assessment of surrounding buildings influence on building NV behaviour is done through validated CFD models. Some parameters and visualizations are proposed to be used in the quantitative and qualitative assessment of each solution respectively. Then, the best location alternative with regards to NV performance is selected. Finally, the research is concluded with the case study building full-scale construction. The indoor CFD simulation used from the beginning is then successfully validated. The NV building behaviour is also successfully verified. Additionally, contrasted performance indexes are used to evaluate indoor comfort conditions: draught risk (DR), predicted mean vote (PMV) and predicted percentage of dissatisfied people (PPD). The results show that comfort conditions can be reached more energy efficiently by means of NV use. Afterwards, it is verified how the comfortable indoor environment conditions are ensured and optimized by the NV use. Although the design strategy is applied to a particular building design, the design strategy potential is that it could be applied to all buildings. Consequently, major potential energy savings could be achieved.
Durante las últimas décadas los agentes involucrados en el diseño de edificios deben de utilizar estrategias fiables de diseño que les permitan aprovechar los recursos naturales del entorno con el objetivo de aumentar la eficiencia energética de los edificios así como promover el desarrollo sostenible y generar valor añadido para la sociedad. Esta tesis propone una estrategia de diseño fiable de edificios para mejorar su eficiencia energética mediante el uso de la ventilación natural (NV por sus siglas en inglés "natural ventilation"). La estrategia consiste en evaluar la solución arquitectónica más adecuada teniendo en cuenta las condiciones ambientales y el entorno de los edificios con el objetivo de maximizar el uso de la ventilación natural desde la fase inicial de su diseño. En esta tesis se aplica la estrategia de diseño a un caso de estudio real y particular. La estrategia de diseño se basa en el uso de un código numérico comercial que resuelve las ecuaciones de la mecánica de fluidos (CFD por sus siglas en inglés "computational fluid dynamics"). El software CFD simula las características que influyen en la ventilación natural y predice su comportamiento en los edificios antes de su construcción. Esta técnica numérica permite la visualización del flujo de aire en los edificios. Además, el software permite calcular parámetros que son analizados y comparados posteriormente para elegir la solución arquitectónica que suponga un mejor comportamiento de la ventilación natural. Con respecto a todas las decisiones arquitectónicas posibles, la investigación se centra en la selección de la ubicación del edificio y de la configuración de los huecos de su fachada. En primer lugar, se analiza la viabilidad de la estrategia de diseño en una región determinada: la zona costera Mediterránea de la Comunidad Valenciana. La región se caracteriza por las condiciones uniformes del viento predominante durante la estación cálida. A continuación, se utiliza una simulación de CFD validada para analizar cualitativamente y cuantitativamente la influencia de los edificios circundantes en los flujos del viento a través y alrededor de los edificios circundantes. El objetivo es comparar distintas posiciones de los huecos de la fachada para seleccionar la alternativa que mejor aproveche los recursos de ventilación natural disponibles. Además, se presenta en el marco de la selección de la configuración de la fachada una cuantificación general de la contribución de la fachada ventilada a la eficiencia energética de los edificios. En segundo lugar, se realizan dos simulaciones para analizar dos ubicaciones diferentes del edificio caso de estudio. La evaluación de la influencia de los edificios circundantes en el comportamiento de la ventilación natural del edificio caso de estudio se realiza mediante la utilización de modelos CFD validados. Se proponen distintos parámetros y visualizaciones para la evaluación cuantitativa y cualitativa de cada solución. A continuación se selecciona la mejor ubicación con respecto al comportamiento de la ventilación natural en el edificio caso de estudio. Finalmente, la investigación concluye con la construcción a escala real del edificio caso de estudio. Se valida con éxito la simulación CFD del interior del edificio utilizada desde la etapa de diseño. También se verifica con éxito el comportamiento de la ventilación natural del edificio. Además, se analizan las condiciones de confort interiores mediante la evaluación de los siguientes índices: riesgo de corrientes de aire (DR por sus siglas en inglés "draught risk"), voto promedio previsto (PMV por sus siglas en inglés "predicted mean vote") y el porcentaje previsto de personas insatisfechas (PPD por sus siglas en inglés "predicted percentage of dissatisfied people"). Los resultados muestran que el uso de la ventilación natural permite alcanzar, de manera más energéticamente eficiente, las
Durant les últimes dècades els agents involucrats en el disseny d'edificis utilitzen estratègies fiables de disseny que els permeten aprofitar els recursos naturals de l'entorn amb l'objectiu d'augmentar l'eficiència energètica dels edificis així com promoure el desenvolupament sostenible i generar valor afegit per la societat. Aquesta tesi proposa una estratègia fiable de disseny d'edificis per a millorar la seva eficiència energètica mitjançant l'ús de la ventilació natural (NV per les sigles en anglès "natural ventilation"). L'estratègia consisteix a avaluar la solució arquitectònica més adequada tenint en compte les condicions ambientals i l'entorn dels edificis amb l'objectiu de maximitzar l'ús de la ventilació natural des de la fase inicial del seu disseny. En aquesta tesi s'aplica l'estratègia de disseny a un cas d'estudi real i particular. L'estratègia de disseny es basa en l'ús d'un codi numèric comercial que resol les equacions de la mecànica de fluids (CFD per les sigles en anglès "computational fluid dynamics"). El programari CFD simula les característiques que influeixen en la ventilació natural i prediu el seu comportament en els edificis abans de la seva construcció. Aquesta tècnica numèrica permet la visualització del flux d'aire en els edificis. A més, el programari permet calcular paràmetres que són analitzats i comparats posteriorment per triar la solució arquitectònica que supose un millor comportament de la ventilació natural. Pel que fa a totes les decisions arquitectòniques possibles, la investigació es centra en la selecció de la ubicació de l'edifici i de la configuració de les obertures de la façana. En primer lloc, s'analitza la viabilitat de l'estratègia de disseny en una regió determinada: la zona costanera Mediterrània de la Comunitat Valenciana. La regió es caracteritza per les condicions uniformes del vent predominant durant l'estació càlida. A continuació, s'utilitza una simulació de CFD validada per analitzar qualitativament i quantitativament la influència dels edificis circumdants en els fluxos del vent a través i al voltant dels edificis circumdants. L'objectiu és comparar diferents posicions dels buits de la façana per seleccionar l'alternativa que millor aprofite els recursos de ventilació natural disponibles. A més, en el marc de la selecció de la configuració de la façana es presenta una quantificació general de la contribució de la façana ventilada a l'eficiència energètica dels edificis. En segon lloc, es realitzen dues simulacions per analitzar dues ubicacions diferents de l'edifici cas d'estudi. L'avaluació de la influència dels edificis circumdants en el comportament de la ventilació natural de l'edifici cas d'estudi es realitza mitjançant la utilització de models CFD validats. Es proposen diferents paràmetres i visualitzacions per a l'avaluació quantitativa i qualitativa de cada solució. A continuació es selecciona la millor ubicació pel que fa al comportament de la ventilació natural a l'edifici cas d'estudi. Finalment, la investigació conclou amb la construcció a escala real de l'edifici cas d'estudi. Es valida amb èxit la simulació CFD de l'interior de l'edifici utilitzada des de l'etapa de disseny. També es verifica amb èxit el comportament de la ventilació natural de l'edifici. A més, s'analitzen les condicions de confort interiors mitjançant l'avaluació dels següents índexs: risc de corrents d'aire (DR per les sigles en anglès "draught risk"), mitjana de vots previstos (PMV per les sigles en anglès "predicted mean vote") i el percentatge previst de persones insatisfetes (PPD per les sigles en anglès "predicted percentage of dissatisfied people"). Els resultats mostren que l'ús de la ventilació natural permet assolir, de manera més energèticament eficient, les condicions de confort.
Mora Pérez, M. (2017). Computational fluid dynamics (CFD) applied to buildings sustainable design: natural ventilation. Case study [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/86208
TESIS

Building ventilation is crucial for improving the indoor air quality and thermal comfort. Nowadays, mechanical ventilation systems such as air conditioning and fans are most commonly used in buildings. However, these devices consume a lot of electricity which is mainly generated from the combustion of fossil fuels, resulting in the release of greenhouse gases and thereby contributing to climate change. Consequently, it is essential to switch to natural ventilation systems which are environmentally friendly as they are based on renewable sources of energy. One such type of natural ventilation system is the solar chimney which can either be roof-mounted or wall-mounted in buildings. The aim of this study was to develop a mathematical model for assessing the thermal performance of roof-mounted (inclined) and wall-mounted (vertical) solar chimneys. The model was validated using numerical simulations in MATLAB. Different configurations of solar chimneys were designed and modelled in MATLAB in order to compare their performances, in terms of the ventilation rate expressed as the number of air changes per hour, ACH. Raw climatic data, including the intensities of global and diffuse solar radiation on a horizontal plane, wind speed and ambient temperature were obtained for Stellenbosch, located in the Western Cape Province of South Africa. This was used for the MATLAB modelling of the solar chimneys. The effects of inclination angle, air gap, chimney height and view factor on the thermal performance of solar chimneys were explored in this study.

The thesis is concerned with the theme of energy savings in the Building industry. It describes passive house development in detail with a focus on the construction part of buildings with low energy consumption. At first, there is an overview of the actual situation concerning the new European Union’s restrictions and a basic classification of energy efficient buildings is introduced. Further, construction compositions in two energy standards are designed for a few selected construction systems suitable for a passive house. They are evaluated from different points of view and compared to each other. Finally, an estimate of the passive house value is given as well as return of extra investments with regards to energy price increase. Key words The thesis is concerned with the theme of energy savings in the Building industry. It describes passive house development in detail with a focus on the construction part of buildings with low energy consumption. At first, there is an overview of the actual situation concerning the new European Union’s restrictions and a basic classification of energy efficient buildings is introduced. Further, construction compositions in two energy standards are designed for a few selected construction systems suitable for a passive house. They are evaluated from different points of view and compared to each other. Finally, an estimate of the passive house value is given as well as return of extra investments with regards to energy price increase. Key words The thesis is concerned with the theme of energy savings in the Building industry. It describes passive house development in detail with a focus on the construction part of buildings with low energy consumption. At first, there is an overview of the actual situation concerning the new European Union’s restrictions and a basic classification of energy efficient buildings is introduced. Further, construction compositions in two energy standards are designed for a few selected construction systems suitable for a passive house. They are evaluated from different points of view and compared to each other. Finally, an estimate of the passive house value is given as well as return of extra investments with regards to energy price increase.

This study sought to demonstrate the potential applications of the solar chimney for the naturally ventilating a building. Computational fluid dynamics (CFD) was used to model various room configurations to assess ventilation strategies. A parametric study of the solar chimney system was executed, and three-dimensional simulations were compared and validated with experiments. A new definition for the hydraulic diameter that incorporated the chimney geometry was developed to predict the flow regime in the solar chimney system. To mitigate the cost and effort to use experiments to analyze building energy, a mathematical approach was considered. A relationship between small- and full-scale models was investigated using non-dimensional analysis. Multiple parameters were involved in the mathematical model to predict the air velocity, where the predictions were in good agreement with experimental data as well as the numerical simulations from the present study. The second part of the study considered building design optimization to improve ventilation using air changes per hour (ACH) as a metric, and air circulation patterns within the building. An upper vent was introduced near the ceiling of the chimney system, which induced better air circulation by removing the warm air in the building. The study pursued to model a realistic scenario for the solar chimney system, where it investigated the effect of the vent sizes, insulation, and a reasonable solar chimney size. It was shown that it is critical to insulate the backside of the absorber and that the ratio of the conditioned area to chimney volume should be at least 10. Lastly, the application of the solar chimney system for basement ventilation was discussed. Appropriate vent locations in the basement were determined, where the best ventilation was achieved when the duct inlet was located near the ceiling and the exhaust vent was located near the floor of the chimney. Sufficient ventilation was also achieved even for scenarios of a congested building when modeling the presence of multiple people.
Ph. D.

Natural ventilation is a passive cooling method that has significant potential to reduce building energy consumption and to positively contribute to indoor environmental conditions. Because the window is an important element in naturally ventilated buildings, it can be used to adjust indoor air flow. However, lack of knowledge about occupants‘ window control behaviour and how this relates to different window typology would result in discrepancy between actual and proposed building performance. And also, limit the potential of natural ventilation in the building. This thesis explores the relationship between indoor air velocity, occupants‘ window control behaviour and window design. This study is based on field measurement and occupant comfort survey in four office buildings in a hot and humid climate in South-east China. The field study was carried in September and October of 2012. The indoor and outdoor thermal conditions, indoor air flow speed, window state and effective opening area were monitored. Occupant thermal comfort questionnaires were given to participants four times a day to record their comfort perceptions in the office. The field study gives new insights into the correlation between indoor air speed, occupants‘ window control behaviour and window design. For the research 14400 set of indoor and outdoor temperature and relative humidity data, 174560 indoor air velocity records and 1344 copies of questionnaires were collected. The results of this study defined comfort zone for this climate which is consistent with Givoni‘s comfort zone for a hot and humid climate. The indoor air flow path is identified by measuring the indoor air velocity across different parts of the office and related window opening combinations. Besides, the effective opening area is reduced with decreased indoor air temperature when the indoor air temperature is lower than 25°c. None of the windows is closed when the indoor air temperature is higher than 28°c. During the working hours, the changing of effective opening is related to the air velocity across the desk surface. And measured maximum indoor air velocity measured around the occupant is 1.8m/s which did not result in occupants‘ window changing behaviour to adjust for comfort. In conclusion, this study proved that occupants who live in hot and humid climate can accept higher humidity level. If the air velocity can be avoided across the occupant‘s working surface, then a higher indoor air velocity is still accepted by occupant as within their comfort threshold. So, there are great potentials for occupant to extend their comfort threshold and adapt to the local climate. Besides, window opening type and position has a significant impact on indoor air velocity and pattern. It would also influence convective cooling affect and occupant thermal comfort. This is evident from the indoor air velocity measurement results and the occupant comfort survey results. In addition, accessibility is important to window design. In the naturally ventilated office building, if occupants find it difficult to operate the window, this will have an influence on the natural ventilation potential in the building and cause the occupant discomfort. Thus, the findings of this study will help architects and engineers to design naturally ventilated office buildings in South-east China.

The aim of this study was to determine the level of environmental impact and primary energy resulting from demands placed on residential ventilation and heating systems; a conventional residential house built to the 2007 Norwegian building code with a standard heating system was compared against three technology scenarios used in a passive house of the equivalent size. Both houses have wooden framework and cladding and are projected by the Norwegian building company Norbohus. An economical evaluation of the heating systems was also done. The alternative heating option for the conventional house, Stord TEK 07, was based on current Norwegian energy consumption patterns; a combination of electricity and firewood is used to meet heating demand. This heating mix was also modeled as an option for the heating requirements of the passive house, named Stord Passive S1. Additionally, a solar collector system (Stord Passive S2) and an air-to-water heat pump (Stord Passive S3) were modeled for the passive house. Finally, a balanced mechanical ventilation system was evaluated for both buildings. The life-cycle assessment method used was the ReCiPe method and the electricity used in the operation phase was based on the Nordic electricity mix.The results of this study indicate that Stord TEK 07 has the largest emission output in relation to output of CO2-eq, presented in the impact category “Climate change”. From a life-cycle perspective, the heating system requirements of a Stord TEK 07 house are 47.5 and 45 percent higher than the renewable energy solutions of passive house scenarios S2 and S3, respectively. Total life-cycle primary energy requirements in the Stord TEK 07 house were almost twice that of the renewable solutions in the passive house. Using the Norwegian standard heating system of Stord TEK 07 in a passive house as was done in Stord Passive S1, also results in a large improvement; output of CO2-eq and use of primary energy was reduced by 34-35 percent. Stord TEK 07 has also the highest emission output in most of the other impact categories and the largest present value costs, when building constructing costs are excluded. The heat pump solution, Stord Passive S3, has the lowest impact in most categories; however, the solar collector system Stord Passive S2, had lower output of CO2-eq. Stord Passive S2 has also lower present value costs then the air-water heat pump Stord Passive S3.A balanced ventilation system with 80 percent heat recovery was studied for both the houses. The benefit of heat recovery is recognizable in all the impact categories considered. The energy consumption and potential harmful emissions resulting from the electrical energy used by fans during the life cycle far exceed the environmental impacts that result from manufacture and transportation of the ventilation unit. The study revealed that the heat-recovery system must have efficiency greater than 15 percent to achieve reduction concerning output of CO2-eq and use of primary energy for Stord TEK 07; this requirement increases to 42 percent in houses built to the passive house standard house, Stord Passive.