Exergy analysis has been found to be a useful method for improving the conversion efficiency of energy resources, since it helps to identify locations, types and true magnitudes of wastes and losses. It has also been applied for other purposes, such as distinguishing high- from low-quality energy sources or defining the engineering technological limits in designing more energy-efficient systems. In this doctoral thesis, the exergy analysis is widely applied in order to highlight and demonstrate it as a significant method of performing energy assessments of buildings and related energy supply systems. It aims to make the concept more familiar and accessible for building professionals and to encourage its wider use in engineering practice. This thesis is divided into five main cases studies, which have different scopes and follow slightly different approaches but all with the same common objective. Case study I aims to show the importance of exergy analysis in the energy performance assessment of eight space heating building options evaluated under different outdoor environmental conditions. This study is concerned with the so-called “reference state”, which in this study is calculated using the average outdoor temperature for a given period of analysis. Primary energy and related exergy ratios are assessed and compared. Higher primary exergy ratios are obtained for low outdoor temperatures...

Com a crise energética e o alto consumo de eletricidade, é crescente a preocupação com a economia de energia, principalmente em edifícios dos setores públicos e comerciais, pois são os grandes consumidores. Com isso, muitos pesquisadores da área estão direcionando suas pesquisas científicas para o estudo do conforto térmico do homem, em busca de edifícios mais eficientes energeticamente. Baseado nesses fatos, esse trabalho avalia a influência de parâmetros construtivos com relação ao consumo de energia e ao conforto térmico de edifícios de escritórios da cidade de São Carlos, de forma a adequar os edifícios ao clima da cidade. Para tal análise, foram estudados seis edifícios com relação à caracterização construtiva, dos quais três foram escolhidos para o levantamento do padrão de uso e ocupação desse tipo de edificação, e para monitoramento de temperatura e umidade relativa do ar. Foram realizadas para o clima da cidade, simulações de um edifício de referência que apresenta alguns parâmetros fixos, que foram adotados por representarem os sistemas construtivos mais utilizados no Brasil, e outros variáveis como a orientação, sistema construtivo, porcentagem de vidro na fachada, absortância da fachada e da cobertura e renovações de ar. Cada parâmetro variável foi simulado com todos os outros fixos...

Building plan and shape are the result of a complex process. Functional, technical and aesthetic considerations all contribute to the building design. Wind, solar availability, shelter, exposure, air quality and noise conditions will affect the relationship between the building and its external environment and influence the shape and the design of the envelope. Materials selection, heating, cooling, daylighting, indoor air quality (IAQ), acoustic behaviour and energy strategies should be meshed at an early stage with the other requirements to ensure the buildings sustainability and overall comfort conditions. To accomplish this goal it is necessary to predict the thermal, acoustic, lighting and IAQ behaviour of the buildings, on the design phase, in order to be able to do the right choices, regarding, for instance the geometry, fenestration strategies, construction solutions and materials, to improve the occupants overall comfort and, simultaneously, to reduce the energy costs and increasing the sustainability of the buildings. So it is necessary to have an integrated approach to ensure the best overall behaviour taking into account all of the, sometimes incompatible, comfort and sustainability requirements. The aim of this study is to select a range of optimized solutions (envelope construction solutions...

During the last decades façade technologies have undergone to substantial innovations by integrating specific elements to adapt the mediation of the outside conditions to user requirements. This work reports the results of an ongoing investigation on a new façade system concept called "Façade Modules for Eco-Efficient Refurbishment of Buildings" and initially developed for Portugal. In this phase glazing modules made of high performance glasses were studied. Some results of thermal performance simulation for the Portuguese Guimarães city climate will be presented considering the use of three types of glazing modules and analyzing the influence of some parameters in heating and cooling energy needs for one room (size 25m²). Computational simulation was done with the Design Builder software considering the following parameters: three different double glazing types; two envelope types and four solar orientations. The results were obtained for heating and cooling energy needs and were compared to all glazing types. It can be noted a better performance to glazing compositions that combines solar control and self-cleaning glass with extra clear glass. The results indicated a decrease of heating energy needs by the use of self-cleaning glass and clear float glass. Additionally cooling energy needs decrease was observed by the use of a green solar control glass with low-e glass.; COST...

As Men spend about 90% of their time inside enclosed spaces, a healthy and comfortable indoor climate is a basic premise in all buildings. Taking into consideration that in the EU, buildings account for about 40% of the total energy consumption (35% in Portugal), it is mandatory to control the energy consumption in the building sector, while maintaining, or even improving, the indoor environmental quality. As the buildings are complex systems, where all aspects are interconnected and influence each other, it is necessary an integrated and comprehensive approach to the building in order to enhance indoor health and comfort besides only energy savings concerns. An environmentally sustainable approach should then be followed. Heating, cooling, daylight, indoor air quality (IAQ), acoustic behaviour and energy strategies should be meshed at an early stage with the other buildings requirements to ensure their overall comfort conditions. To accomplish this goal, it is necessary to predict the thermal, acoustic, daylight conditions and IAQ behaviour of the buildings, on the design phase, in order to be able to do the right choices, regarding, for instance the geometry, space organization, fenestration strategies, construction solutions and materials...

New legislation and incentives have been created, showing that there is an attempt to act and to intervene in energy efficiency area. Energy consumption reduction and prevention of energy waste is one of the main objectives of the European Union (EU). Building facades constitute a privileged component to propose solutions, once it has a major influence in the energy consumption in the building and in occupants comfort; because it has elements that contribute significantly with the heat transfer. This paper presents a study on about a new facade concept: "Facade Modules for Eco-Efficient Refurbishment of Buildings", especially on thermal performance of glazing modules. Computational simulation was done with the Design Builder software for ten different double glazing types (composed by green and transparent solar control glass, self-cleaning glass, two low-e glasses types, two extra clear glass) for two climates in Portugal (Coimbra and Faro) and four solar orientations (north, south, east and west). The results were obtained for heating and cooling energy necessities and were compared to all glazing types. These results showed a better performance to glazing compositions that combines solar control and self-cleaning glass with extra clear glass to both cities. Facades with green solar control glass and extra clear glass presented a better performance in comparison with others types studied...

The few available sustainability assessment tools applicable in Portugal are oriented for residential buildings. Nevertheless, the impacts of office buildings have been rising mainly due to an increase in the energy consumption for cooling and heating. This way, due to the growing environmental impact of office buildings, the development of Build-ing Sustainability Assessment (BSA) tools to assess the sustainability of this type of buildings is necessary and important to guide and to boost the construction sector to-wards sustainable development. The main objective of this work was to develop a sustainability assessment tool aimed at office buildings based in SBToolPT-H and was performed using the experience acquired in Master in Sustainable Construction and Rehabilitation (MCRS) The work includes the definition of the tool’s framework and assessment method, as well as Portuguese benchmarks and weighting system used in the aggregation. In order to promote the practical use of this tool, an evaluation guide was also developed in which there are detailed information about calculation methods and aggregation models. The methodology presented in this paper is based on a list of indicators that are assessed by comparison with Portuguese reference practices (benchmarks).

The purpose of this paper is to develop a relative evaluation, from the energetic point of view, of different building layouts. Buildings can be classified, according to their position within the lot, as perimeter yard buildings, rear yard buildings, and side yard buildings. This classification covers the layout solutions traditionally adopted by architects for 2-floor residential buildings. The thermal performance of each building layout was evaluated through the quantification of its energetic consumption (per square meter of built area), for the heating and cooling seasons, and according to the geographic orientation. The simulation tool used in this evaluation is based on the Transfer Function Method. The results obtained showed that the rear yard buildings have the better thermal performance, with an average energy consumption that is around 40% lower than in the other cases. In addition, for all building layouts studied, the North-South orientation requires the minimum energetic consumption to maintain comfortable indoor air temperature.; Fundação para a Ciência e a Tecnologia (FCT)

Acknowledgements : the authors wish to thank FCT (Fundação para a Ciência e Tecnologia – Portugal) and COMPETE (Programa Operacional de Fatores de Competitividade - Portugal) for supporting the ADjustMEMBRANE project with the reference PTDC/AUR-AQI/102321/2008.; Construction industry is responsible for great environmental impacts in the world, some authors refer that these can be as high as 50% of the global impacts. The research for lower environmental impact constructive solutions, namely by the weight reduction is thus a main concern when the objective is to reduce the footprint of buildings, especially in urban areas. Textile membranes are usually used to cover big spans with complex geometries, using the special properties of the Hypar (Hyperbolic paraboloid). However it is possible to use membranes on small external façades and coverings, with low spans, not only as sandwich panels, but also as a junction of small Hypar modules, with still their mechanical special properties well explored, allowing a very small weight and thus a good environmental performance, compared to conventional façade and covering solutions. Apart from this, the research on membrane materials for thermal regulation, allows to extend its possibilities in order to fulfil contemporary demands of comfort...

Dissertação de mestrado integrado em Engenharia Civil; A saúde e o bem-estar em locais de trabalho são dois pré-requisitos fundamentais para a existência de um bom desempenho dos seus ocupantes. Assim, a permanência prolongada de trabalhadores no interior de locais de trabalho fechados pode prejudicar a sua saúde e reduzir a produtividade da empresa e consequentemente acarretar prejuízos financeiros. É neste contexto que a ventilação natural desempenha um papel importante no controle dos níveis de poluição no interior de edifícios. Todavia as condições de conforto térmico também devem ser tidas em conta, uma vez que o calor ou frio excessivo contribuem para a redução de produtividade e para o aumento de queixas dos utilizadores, e para maiores consumos energéticos de climatização. Para compreender como estes três parâmetros se correlacionavam foram realizadas medições in situ da qualidade do ar interior e foram administrados inquéritos aos ocupantes de dois edifícios de serviço. Estas medições contribuíram para a identificação das principais fontes de poluição, das condições de conforto térmico e da perceção dos ocupantes relativamente ao ambiente interior de edifícios desse tipo. Os resultados das medições da qualidade do ar e a análise do desempenho dos edifícios mostraram que as condições da qualidade do ar interior e do conforto térmico não eram adequadas...

Exploring changes of building energy consumption and its relationships with climate can provide basis for energy-saving and carbon emission reduction. Heating and cooling energy consumption of different types of buildings during 1981-2010 in Tianjin city, was simulated by using TRNSYS software. Daily or hourly extreme energy consumption was determined by percentile methods, and the climate impact on extreme energy consumption was analyzed. The results showed that days of extreme heating consumption showed apparent decrease during the recent 30 years for residential and large venue buildings, whereas days of extreme cooling consumption increased in large venue building. No significant variations were found for the days of extreme energy consumption for commercial building, although a decreasing trend in extreme heating energy consumption. Daily extreme energy consumption for large venue building had no relationship with climate parameters, whereas extreme energy consumption for commercial and residential buildings was related to various climate parameters. Further multiple regression analysis suggested heating energy consumption for commercial building was affected by maximum temperature, dry bulb temperature, solar radiation and minimum temperature...

Commercial office buildings predominantly are designed to be ventilated and cooled using mechanical systems. In temperate climates, passive ventilation and cooling techniques can be utilized to reduce energy consumption while maintaining occupant comfort using natural ventilation. However, current modeling techniques have limitations and assumptions that reduce their effectiveness in predicting internal building performance. There are few tools to predict the thermal performance of and resulting airflow patterns in naturally ventilated office buildings accurately. This thesis presents three significant contributions for the evaluation of natural ventilation in buildings: * A methodology for assessing the performance of naturally ventilated buildings through a reduced-scale air model was developed based on dimensional analysis and similitude criteria. Buoyancy, wind, and combined ventilation strategies for a multi-zoned commercial office building with an open floor plan layout were evaluated using the reduced-scale model. * Guidelines were established for monitoring natural ventilated buildings as a means to evaluate their operation, based on field measurements of a prototype building were established. * A framework for evaluating current techniques for modeling airflow patterns in naturally ventilated buildings was developed...

The installation of cool roofing in urban areas is a practical mitigation measure to reduce the Urban Heat Island (UHI) effect and is currently being implemented in many cities around the world to reduce building cooling load demands. The UHI effect results from surface and air temperatures of urban areas being higher than rural areas due to the thermal properties of buildings and reduced vegetative cover. Examples of cool roofs are white vinyl roofs and roofs with reflective coatings. Cool roofs have high albedo (also known as solar reflectivity or solar reflectance) which helps to reflect sunlight and therefore, reduce roof temperatures. Lower roof temperatures result in lower internal temperatures within buildings and this significantly reduces their cooling load. A street canyon is an representative unit of an urban area whereby a street is flanked by two tall buildings on both sides. The aim of this study was to investigate the effect cool roofing has on the air quality within a street canyon. In this project, an idealised street canyon with a street canyon height-to-width ratio of one was created in a Computational Fluid Dynamics (CFD) model which utilises the Renormalization Group (RNG) k-" turbulence model. In order to verify the model’s ability to simulate thermal effects...

Este trabalho surgiu do âmbito da Tese de Dissertação do Mestrado em Energias Sustentáveis do Instituto Superior de Engenharia do Porto, tendo o acompanhamento dos orientadores da empresa Laboratório Ecotermolab do Instituto de Soldadura e Qualidade e do Instituto Superior de Engenharia do Porto, de forma a garantir a linha traçada indo de acordo aos objectivos propostos. A presente tese abordou o estudo do impacto da influência do ar novo na climatização de edifícios, tendo como base de apoio à análise a simulação dinâmica do edifício em condições reais num programa adequado, acreditado pela norma ASHRAE 140-2004. Este trabalho pretendeu evidenciar qual o impacto da influência do ar novo na climatização de um edifício com a conjugação de vários factores, tais como, ocupação, actividades e padrões de utilização (horários), iluminação e equipamentos, estudando ainda a possibilidade do sistema funcionar em regime de “Free-Cooling”. O princípio partiu fundamentalmente por determinar até que ponto se pode climatizar recorrendo único e exclusivamente à introdução de ar novo em regime de “Free-Cooling”, através de um sistema tudo-ar de Volume de Ar Variável - VAV, sem o apoio de qualquer outro sistema de climatização auxiliar localizado no espaço...

The majority of commercial buildings today are designed to be mechanically cooled. To make the task of air conditioning buildings simpler, and in some cases more energy efficient, windows are sealed shut, eliminating occupants' direct access to fresh air. Implementation of an alternative cooling strategy-mixed-mode cooling-is demonstrated in this thesis to yield substantial savings in cooling energy consumption in many U.S. locations. A mixed-mode cooling strategy is one that relies on several different means of delivering cooling to the occupied space. These different means, or modes, of cooling could include: different forms of natural ventilation through operable windows, ventilation assisted by low-power fans, and mechanical air conditioning. Three significant contributions are presented in this thesis. A flexible system identification framework was developed that is well-suited to accommodate the unique features of mixed-mode buildings. Further, the effectiveness of this framework was demonstrated on an actual multi- zone, mixed-mode building, with model prediction accuracy shown to exceed that published for other naturally ventilated or mixed-mode buildings, none of which exhibited the complexity of this building. Finally, an efficient algorithm was constructed to optimize control strategies over extended planning horizons using a model-based approach. The algorithm minimizes energy consumption subject to the constraint that indoor temperatures satisfy comfort requirements. The system identification framework was applied to another mixed-mode building...

Buildings are one of the world's largest consumers of energy, yet measures to reduce energy consumption are often ignored during the building design process. In developing countries, enormous numbers of new residential buildings are being constructed each year, and many of these buildings perform very poorly in terms of energy efficiency. One of the major barriers to better building designs is the lack of tools to aid architects during the preliminary design stages. In order to address the need for feedback about building energy use early in the design process, a model was developed and implemented as a software design tool using the C++ programming language. The new program requires a limited amount of input from the user and runs simulations to predict heating and cooling loads for residential buildings. The user interface was created with the architect in mind, and it results in direct graphical comparisons of the energy requirements for different building designs. The simulations run hour by hour for the entire year using measured weather data. They typically complete in less than two seconds, allowing for very fast comparisons of different scenarios. A set of simulations was run to perform a comparison between the new program and an existing tool called Energy-10. Overall...

Building energy simulation is an important tool for evaluating the energy consumption of a building and can provide guidance in the design of a building and its mechanical systems. EnergyPlus is a new energy simulation program meant to be a major advance over existing energy simulation programs. This study uses EnergyPlus to compare several alternative low-energy cooling systems for an office building in suburban London and compare them to the chilled ceiling system installed in the actual building. Prior to modeling the full -scale building, several validation studies demonstrate the accuracy of EnergyPlus and the author's competency as an EnergyPlus user. Systems considered include displacement ventilation, traditional mixing variable air volume ventilation, night cooling, and natural ventilation. Several changes were made to the EnergyPlus source code to model these systems appropriately. Most notable are a displacement ventilation three-node vertical temperature gradient model and a simple model for prediction of the natural ventilation rate. A detailed building model is created from inputs gathered from both building design documents and measured data. An excellent comparison between simulated and measured space temperatures over a one-month period demonstrates the accuracy of the model. System comparisons show that systems using free cooling from outside air and night cooling use the least energy and have the smallest equipment. Natural ventilation alone is insufficient to maintain summer comfort within the building...

A adoção de sistemas de gestão da qualidade no setor da construção civil tem sido uma constante na busca pelo aumento da competitividade, pela melhoria da qualidade com a minimização de erros e redução dos custos no processo de projeto e execução, especialmente no setor de produção das edificações. No que se refere aos projetos de reabilitação de edifícios históricos, a abordagem proposta por estes sistemas é considerada pertinente devendo, entretanto, ser particularizada incorporando os valores relacionados a esse tipo especial de projeto. Entre os fatores a serem considerados na reabilitação das edificações está a compatibilização entre os projetos das especialidades Nesse contexto, merece destaque o projeto de climatização dos edifícios históricos. Este tipo de projeto, por caracterizar intervenções quase sempre agressivas e predatórias, possui relevante influência e pode vir a ser o principal norteador da intervenção, conforme o caso. O presente artigo se propõe a apresentar uma análise do processo de projeto de reabilitação de edifícios históricos com ênfase no impacto do projeto de climatização. A proposta toma por base as informações divulgadas nos Manuais de Projeto Básico e Projeto Executivo de Restauração do Patrimônio Edificado do IPHAN e no Manual de Escopo de Serviços de Ar Condicionado e Ventilação – Indústria Imobiliária...

There is a growing energy demand for cooling in European buildings. It is expected that the cooled floor area will be four times higher in 2020 when compared with 1990 figures. Cooling is already the energy use in the building sector with the highest increase rate. This evidence is not contributing to the overall objective of reduction CO2 emissions. The conventional answer to this problem is to improve of the energy efficiency of cooling. However, this strategy showed limited results in terms of saving energy and reducing greenhouse gas emissions. In fact, cooling can be avoided (or the need to use energy for cooling) or significantly reduced without risking summer thermal comfort for building occupants, having thus the potential to achieve substantial reductions in energy demand. However, avoidance or even major reduction of cooling implies a new approach in building design, construction and operation phases. Different scientific and technological advances shall coherently be used and be offered to building promoters or building owners as a new service. The new adaptive comfort theory, the possibility for local adaptation for building users and facilities, the capability to intervene in the surrounding urban environment, the use of mature passive cooling solutions...

Four sustainable alternative-energy cooling system options are investigated to quantify the actual energy that may be saved when employed in conjunction with conventional air conditioning systems. The four systems considered are active mass cooling, night flushing, roof-spraying and a roof-pond. A one-room building configuration is assumed of which the hourly cooling load and temperature is modelled for both a base case and different combinations of the four sustainable cooling alternative systems. Active mass cooling, night flushing and the roof-spray system proved to be viable options in which the cooling load of an air conditioner may be reduced to maintain a constant room temperature. The roof-spray system showed the most effective results in limiting heat gains to the one-room building and keeping peak room temperatures low.