Climatic stress on buildings in hot-dry climates has long been negotiated by means of evaporative cooling, the origins of which could be traced back to Egypt and the Middle East. However, this millennia-old strategy needs to undergo much scrutiny in its design and implementation to meet the requirements of contemporary comfort standards for offices. The task is even more onerous if multi-storey buildings are considered. Acknowledging Cairo to be one of the most densely populated cities in the world and in light of the growing demand on high quality office space in recent years, it is anticipated that extending the application of evaporative cooling to medium and high-rise office buildings is imperative if this strategy is to be widely adopted as an alternative to conventional air-conditioning in Cairo given that existing research and applications are limited to low-rise buildings. This work proposes a four-stage plan to achieve that. The first stage entails the development of a generic prototype of the Passive Downdraught Evaporatively Cooled (PDEC) multi-storey office building that allows three distinct airflow patterns and two modes of operation to take place. The second stage makes use of analytic models for the initial sizing of the airflow components. The third stage assesses the performance of a base case model of the generic PDEC building in terms of bulk airflow rates, airflow distribution across the floors, internal thermal conditions, and relevant environmental costs using EnergyPlus, the whole building dynamic thermal simulation program with integrated airflow network modelling. The fourth and final stage is that of optimisation wherein the effects of varying a number of parameters on performance are established. The study shows that in comparison to free-running naturally-ventilated buildings, and depending on the thermal comfort model adopted, PDEC can potentially deliver comfort conditions for all occupied hours of the cooling season in Cairo. Buoyancy 'stack' forces alone generated by temperature differences can drive sufficient airflow rates without wind assistance, a scenario that is likely to occur in dense urban contexts. The study demonstrates the effectiveness' of dividing multi-storey buildings into isolated segments in terms of airflow (segmentation) and the benefits of extending PDEC operation beyond occupied hours. Changes in wind direction and speed were also considered and have shown to be of less significance if air inlets and outlets are properly located. Fine tuning of the building management system and adopting a more relaxed overheating criterion are key factors in limiting the increase in daily water consumption due to PDEC in light of the diminishing availability of sustainable water resources in the region. This study is the first to provide an understanding of how multi-storey office buildings in hot-dry climates can be designed and operated to incorporate PDEC as a viable alternative to AC. The novelty here lies not in the methodology which uses available models, but in the detailed investigation of flow rates, flow patterns, indoor temperatures, and water consumption.

Thermochromic (TC) windows were developed as a passive building component to improve indoor comfort and building energy conservation in place of traditional clear glazing systems. TC materials enable a spectrum-dependent regulation of solar radiation through windows stimulated by heat. When the temperature is higher than its transition temperature, less solar radiation, primarily in the near infra-red (NIR), will be admitted inside the building, reducing over-heating on hot days. Meanwhile, the TC materials tint to bluish or brownish appearance along with the transition. Most research about the commonly studied Vanadium dioxide (VO2) based TC windows was focused on fabrication methods and properties improvement of VO2 based materials, and a few numbers of studies investigated their energy performance when applied in buildings. Therefore, this research conducted a thorough investigation of TC windows applied in buildings, covering characteristic of TC windows, energy efficient, daylighting performance, and human response affected by different types of TC windows. Both simulation and experimental methods were carried out to explore the potential of TC windows. That aim is to provide a detailed guidance for the development of TC materials that are more flexible and acceptable to use in a practical building. The comprehensive analysis mainly consists of four parts: 1) simulation work on the evaluation of TC windows on energy efficient and daylighting, also the window size effects under five typical climates; 2) further evaluation of the potential of developed TC windows with enhanced capability of adjusting visible and NIR transmittance individually or cooperatively; 3) experimental investigation of the research hypothesis that TC tinted window has no effect on the human visual performance and subjective sensation, in a test room cubicle with a low level of simulated daylit (100lux); 4) further experimental investigation to detect the acceptance range of tinting for different windows at an indoor comfort illuminance level (350 lux). Findings show that compared with reducing the transition temperatures, improving capability of adjusting visible or NIR transmittance is more effective to improve both daylighting and energy performance. TC windows are more energy efficient when applied in buildings with large glazing area under cooling dominated climates. However, dynamic reduction of visible transmittance is required to decrease the risk of visual discomfort caused by over daylighting, especially for cities with lower solar altitude. Under a dark illuminance, bronze tinted TC windows were preferred subjectively, however, subjects had better visual performance under blue tinted TC window conditions. Sustained attention (i.e., focus on an activity for a long period of time) was not affected by TC window conditions (i.e., with correlated colour temperature (CCT) ranging from 3300 to 11000K), but further tinted bronze window was subjectively considered to improve concentration. Therefore, adjustment of visible transmittance is highly recommended for warm tinted TC windows. Simulation and lab experiment might have some limitation on this study, further work is suggested by carrying out further validation and employing more samples.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

This thesis examines the use of aerial thermography data to discriminate loft (attic) insulation levels in residential housing, with ventilated pitched roofs, in the UK. Quantitative techniques from the fields of remote sensing, GIS, building physics and atmospheric science were used to develop a methodology and analyse survey data flown over Nottingham in 2001. The quantitative techniques were applied to real survey data using the most up to date atmospheric propagation models. A new model of the heat loss through the ceiling, loft and roof was developed for this study, based on the most recent methods. The limitations of these techniques were explored. A complete methodology, valid for any future study, was defined. It was found that, measuring roof surface temperature from the thermal image was complicated by roof material properties, the intervening atmosphere and the surrounding topography. Relating roof surface temperature to insulation thickness was further complicated by loft space ventilation and the outside surface heat balance. The additional data, needed to quantify the results, produced inaccuracies caused by measurement error. Analysis of the uncertainties, by simulation, indicated that loft insulation level could not be discriminated by aerial thermography. This was confirmed by comparing the results, calculated from the survey data, with the actual insulation level for a number of houses in test areas of the city.

Monitoring is a process of observing any changes on a monitored subject. Deformation monitoring is a process which consists of four stages: specification, design, implementation and analysis [Kennie et al., 1990], with the structure being monitored on a daily, hourly or continuous basis for any changes in position, size and shape. With the Global Positioning System (GPS), a 24-hour all weather monitoring system can be established. However, for kinematic GPS, un-mitigated troposphere and multipath remain as the main source of errors in the position residuals. These were investigated in detail using data from field trials conducted by the author which suite their particular purposes. The investigations were made using static and moving stations, and included stations at the same altitude, and stations with a high difference in altitude, and baseline lengths of less than ten kilometres. Using Adaptive Filtering (AF) technique, common signals in two time series can be extracted. By performing AF and interchanging position residuals time series as reference and desired (Forward and Backward) using consecutive days of data will show the multipath and this can be confirmed with a third day of data. While same day AF can be used to separate un-mitigated troposphere and movements from receiver noise. The position residuals considered in this thesis were processed with Leica Ski-Pro Version 3.0 software. These were validated and through comparisons made using a kinematic GPS processing software named KINPOS, developed by previous researchers at the IESSG, University of Nottingham and the use of Virtual Reference Station (VRS) data were also investigated by comparing with actual data. Through the field trials carried out on Snowdon, University campus, Humber Bridge and Forth Road Bridge, the novelty of this thesis is that it demonstrates that by better understanding the trends in unmitigated troposphere and multipath, the use of kinematic GPS for monitoring tall structures can be improved, making the results more suitable for engineers and building owners or managers to better assess building performance during extreme motions caused by traffic, earthquakes, strong winds, and other climatic conditions.

Ethylene-tetra-fluoro-ethylene (ETFE) is a synthetic fluoropolymer. In the form of ETFE-foil it is applied in building envelopes in a single layer or more commonly, as inflatable cushions composed of multiple layers. ETFE-foils are widely used as a lightweight building envelope where high translucency, low structural weight, and complex shape is essential. However, limited research in the field of thermal performance of ETFE-foil panels and spaces enclosed with it instigated this study. Therefore, this study investigated (I) the thermal behaviour of ETFE-foil materials and the thermal performance of spaces enclosed with ETFE cushion roofs, (II) used commercially available thermal simulation software to predict the thermal performance of spaces enclosed with ETFE cushion and glass roofs and compared this with actual monitored behaviour (III) identified strategies to improve the thermal performance of spaces enclosed with ETFE cushion roofs in current and projected climate scenarios; and finally (IV) proposed design recommendations of ETFE-foil panels/cushions as a building fabric components. Material properties were investigated in laboratory based experiments. Further data were collected from two custom built outdoor test-rigs equipped with single-, two- and three-layer ETFE-foil panels. Environmental data were collected from two case study buildings to evaluate the thermal performance of the spaces enclosed with ETFE-foil cushion roofs. In addition, building simulation was conducted using EDSL TAS version 9.3.3.b to further analyse the indoor thermal environment and compare with monitored behaviour. The study identified variable thermal-optical properties of ETFE foils caused by various percentages of fritted area and its pigment density. The results also identified that the thermal environment of the test-rigs was affected by the variations in the surface temperatures of ETFE-foils and the temperature of air volume between multiple ETFE-foils (in case of two and three layer panels) by convective and radiative heat transfer mechanisms. The results from the case study buildings identified that during hot summer days, indoor air temperature and temperature stratification was higher in the atrium space enclosed with three-layer ETFE-foil cushions compared to the space enclosed with two-layer ETFE-foil cushion covered with rain mesh. However, both of the spaces were overheated during the summer of 2015. To develop an accurate simulation model for ETFE cushion roofs, a novel approach of modelling was developed. The simulation model was validated and calibrated by comparing with measured data from test-rigs and case study buildings. A comparison of predicted results of the spaces enclosed with a multi-layer ETFE-foil cushion roof and a glass roof showed that the extent of overheating was high when spaces were enclosed with glass roofs. Among two-and three-layer ETFE-foil cushion and glass roofs, two-layer ETFE-foil cushions with 75% fritting and rain mesh effectively reduced air temperature and cooling load during the peak summer period. The findings of this study will enable designers to select and develop design strategies for applying ETFE-foils in building envelopes on the basis of thermal and optical requirements. The study also suggested to change the view of current design practice that only focused on current conditions; such as the use of ETFE-foils may require more adaptive approach to mitigate overheating problems in projected climate.

The energy demand in the oil- dependent Gulf countries in general and in Saudi Arabia in particular has been increasing sharply in the last decades as a result of the diversification plans. Tall building construction, associated with many environmental and ecological challenges, played an essential role in these plans, as a mean to attract new economies based on global placemaking and international tourism. The significant use of air conditioning to cool indoor spaces, particularly in residential buildings, accounts for more than half of all energy consumption in the country, and despite governmental efforts, the scattered conservation efforts have been largely ineffective due to factors such as lack of awareness and information, in addition to the limitation of the local energy efficiency building regulations. This research aimed to find and prioritise building envelope design solutions that can reduce high energy consumption and cooling loads while maintaining indoor environment for residential tall buildings in Saudi Arabia. In order to achieve that, a hypothesis of integrating the thermal properties and design parameters of the building envelope as a design strategy for tall buildings envelope were proposed, and to test it, a mixed method approach was followed including literature review, data collection, dynamic building simulations and parametric analysis. The main findings emphasised how combining both the thermal properties and design parameters of the building envelope can be an effective way to achieve energy efficiency in residential tall buildings in the hot climate of Jeddah. Especially in relation to solar heat gains, the highest contributor to cooling loads in this building type. The findings highlighted that while the thermal properties of the wall type can reduce up to 10% of the cooling loads, applying external shading devices can achieve a reduction of up to 30% in solar gains. Moreover, effective consideration of building orientation can significantly reduce cooling loads by 25% and solar gains by 60% for the perimeter zones. Based on this, a set of guidelines that incorporate a comparative tool were introduced to help designers to determine the thermal performance and energy use of a typical residential tall building in the early stages of the building’s design. Which also aim to enhance the effectiveness of the local building codes and energy efficiency regulations in relation to this building type.

No description available.

As a low concentration concentrator with a larger acceptance angle and without a tracking requirement, compound parabolic concentrator is regarded as an attractive solution to improve the system performance and reduce the cost of photovoltaic (PV) system, solar thermal system, daylighting and lighting systems, etc. As a typical type of three-dimensional compound parabolic concentrator (CPC), dielectric crossed compound parabolic concentrator (dCCPC) has drawn a significant research attention in these years to explore its angular characteristics in solar collection for concentrating photovoltaics and daylighting control in buildings. This thesis provides a comprehensive study on dCCPC in aspect of daylighting control. The work starts from a general review that provides a detailed introduction of the background of CPC applications in solar energy. Then the fundamental property of dCCPC when it is utilized as skylights for daylighting control is investigated, and the performance of dCCPC is also compared to other types of CPC. With the consideration of actual application, the dCCPC panel should be designed as small as possible to reduce its weight and maintain the optical characters simultaneously. Several criteria relating to the dimension of dCCPC panel are proposed and investigated about their effects on the optical performance of dCCPC, followed by the experiments that are taken for validation. As ray-tracing simulation is the most common way to determine the optical performance of dCCPC which provides accurate result but requires long time to run, the multiple nonlinear regression model and artificial neural network model are put forward in the beginning of the second half of this thesis. The coefficients of determination of these models could reach 0.99 which imply the high accuracy of them. The optical performance of dCCPC can be calculated rapidly by knowing the sun position and sky condition. Afterwards, because the performance of dCCPC can be calculated easily for any time and any location with the mathematical model, a case study was taken to investigate the dCCPC effects on building energy consumption, indoor visual environment and economic benefits. This research proves the potential of dCCPC in terms of daylighting control. As a stationary skylight, the transmittance of it is adjusted automatically depending the sky condition and sun position. It also provides outstanding performance in indoor illuminance distribution. The dCCPC is suggested to be used in the locations with long hot seasons for the purpose of energy saving, and it is suggested for all locations with a view to glare control. For further work, more related criteria are encouraged to be added into the prediction models. The method of manufacturing dCCPC is suggested to be improved. Finally, the asymmetric dCCPC is expected to have high potential in daylighting control as vertical building facade, which is worth to be investigated.

With increasing concerns about the implications of climate change and urbanisation, there has been an increased public interest in the quality of urban open spaces in many countries because of its importance for daily people’s lives and urban environment. Recent studies in this field have shown that the microclimatic conditions are very important for people’s comfort in urban open spaces and, therefore, for the use of these spaces. Studying microclimate and thermal conditions in urban open spaces has been increased in the past years. The relationship between the microclimate, thermal comfort and the built urban form is still not understood very well. Further research in this aspect is needed. The courtyard is one of the open space types widely used in the countries of North Africa, Middle East and South Europe. The courtyard is often referred to in literature as a microclimate modifier. Because of this, many studies have been conducted in order to investigate its thermal environment. The majority of these studies dealt with the courtyard as a private space as a part of a building that can contribute to improve the indoor thermal conditions of the surrounding covered areas (its main function is to provide daylight and ventilation into the covered spaces). This study focuses on a particular type of courtyard. It deals with public enclosed courtyards which combine the features of the courtyards and public squares. This type of courtyard is not limited to provide only natural ventilation and natural daylight for the surrounding buildings, but it is mainly designed to offer a public place to perform a variety of activities for people such as social interactions, culture events, recreation, playing, business and many other activities. To the best of my knowledge, there have been no studies done on the microclimate and thermal comfort of courtyards with similar designs (function), particularly in hot dry regions. This study is conducted in Libya where the courtyard is the most common architectural pattern in its cities through all periods of the history. It is conducted in Libya where there is no published research on outdoor thermal comfort. This study investigated the microclimate, thermal comfort and the relationship with the built urban form of public enclosed courtyards in Tripoli city. The general purpose of this study was to develop a database of the thermal environment and subjective responses of people in existing public open spaces in a hot dry climate. The methodology used for this purpose was field studies. Two short-term field surveys were conducted in the two extreme seasons in Libya, one in the cool season day-time and the other one in the hot season day-time. A further field survey was performed during the hot season night-time, where no such study has been conducted in courtyards at this time in the past. In these field studies, extensive environmental measurements have been carried out in parallel to questionnaire surveys with the users of the selected case study sites. Six varied public enclosed courtyards representing three different architecture and urban-built forms of Tripoli city (old city, colonial city, and post-colonial city), were selected for the purpose of this study. The results showed that during both seasons, the microclimatic conditions in the studied courtyards were varied depending mainly on the amount of solar radiation received by their surfaces. Spatial characteristics (architectural form, geometry and surface materials and colours) had important roles in shaping the microclimates of the studied sites during both seasons. The results also showed that the distribution of thermal sensation votes, overall comfort votes and thermal preference votes were different for both seasons, as well as for the sites. Air temperature and then wind speed were found to be the most important determinants of people comfort. The findings of the study also revealed that summer night-time is considered to be of concern for urban thermal comfort in outdoor environments in Tripoli. In general, the findings confirmed a strong relationship between the built urban form (spatial characteristics of the sites), the microclimatic conditions and people’s comfort.