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- Natural ventilation and indoor air quality in educational buildings: experimental assessment and improvement strategiesPublication . Almeida, Ricardo; Pinto, Manuel; Pinho, Paulo G.; Lemos, Luís T. deIndoor environmental conditions in classrooms, in particular temperature and indoor air quality, influence students’ health, attitude and performance. In recent years, several studies regarding indoor environmental quality of classrooms were published and natural ventilation proved to have great potential, particularly in southern European climate. This research aimed to evaluate indoor environmental conditions in eight schools and to assess their improvement potential by simple natural ventilation strategies. Temperature, relative humidity and carbon dioxide concentration were measured in 32 classrooms. Ventilation performance of the classrooms was characterized using two techniques, first by fan pressurization measurements of the envelope airtightness and later by tracer gas measurements of the air change rate assuming different envelope conditions. A total of 110 tracer gas measurements were made and the results validated ventilation protocols that were tested afterward. The results of the ventilation protocol implementation were encouraging and, overall, a decrease on the CO2 concentration was observed without modifying the comfort conditions. Nevertheless, additional measurements must be performed for winter conditions.
- Calibration of the Gipps Car-following Model Using Trajectory DataPublication . Vasconcelos, Luís; Neto, Luís; Santos, Sílvia; Bastos Silva, Ana; Seco, ÁlvaroOne of the most important tasks in the microscopic simulation of traffic flow, assigned to the car following sub-model, is the modelling of the longitudinal movement of vehicles. The calibration of a car-following model is usually done at an aggregated level, using macroscopic traffic stream variables (speed, flow, density). There is an interest in calibration procedures based on disaggregated data. However, obtaining accurate trajectory data is a real challenge. This paper presents a low-cost procedure to calibrate the Gipps car-following model. The trajectory data is collected with a car equipped with a datalogger and a LIDAR rangefinder. The datalogger combines GPS and accelerometers data to provide accurate speed and acceleration measurements. The LIDAR measures the distances to the leading or following vehicle. Two alternative estimation methods were tested: the first follows individual procedures that explicitly account for the physical meaning of each parameter; the second formulates the calibration as an optimization problem: the objective function is defined so as to minimize the differences between the simulated and real inter-vehicle distances; the problem is solved using an automated procedure based on a genetic algorithm. The results show that the optimization approach leads to a very accurate representation of the specific modeled situation but offers poor transferability; on the other hand, the individual estimation provides a satisfactory fit in a wide range of traffic conditions and hence is the recommended method for forecasting purposes.
- Experimental assessment of IAQ improvement in naturally ventilated educational buildingsPublication . Pinto, Manuel; Almeida, Ricardo; Pinho, Paulo; Lemos, Luís; Lanzinha, JoãoIndoor environmental conditions in classrooms, in particular temperature and indoor air quality, influence students’ health, attitude and performance. In recent years several studies regarding indoor environmental quality of classrooms were published and natural ventilation proved to have great potential, particularly in southern European climate. This research aimed to evaluate indoor environmental conditions in 8 schools and to assess their improvement potential by simple natural ventilation strategies. Temperature, relative humidity and carbon dioxide concentration were measured in 32 classrooms. Ventilation performance of the classrooms was deeply characterized by tracer gas measurements of the air change rate assuming different windows related boundary conditions. A total of 110 tracer gas measurements were made. The complete characterization of the classrooms ventilation performance was relevant for the definition of the ventilation protocol since air change rate helped to pinpoint the best ventilation strategy for each case study. The results of the ventilation protocol implementation were very encouraging and, globally, a significant decrease on the CO2 concentration was observed without modifying the comfort conditions. This paper presents and discusses the main conclusions of the measurements campaign performed in the referred classrooms.
- Caracterização Experimental de um Sistema de Ventilação Misto em Edifícios de HabitaçãoPublication . Pinto, Manuel; Freitas, VascoDevido à variação de factores naturais, nomeadamente a direcção e a velocidade do vento e a flutuação da temperatura, os sistemas de ventilação natural nem sempre permitem assegurar as taxas de renovação horária ideais. Para isso consideramos fundamental caracterizar o funcionamento de um sistema de ventilação misto (entradas de ar auto-reguláveis nos quartos e salas, extracção natural nas instalações sanitárias e exaustão mecânica na cozinha) que poderá contribuir para uma estratégia de ventilação de grande interesse. O estudo pretende avaliar qual a melhor constituição de um sistema misto de ventilação e definir regras construtivas a implementar de modo a permitirem alcançar as renovações horárias preconizadas na normalização e regulamentação portuguesa.
- Sistemas de Ventilação Natural/Mistos em Edifícios de Habitação. Implicações ConstrutivasPublication . Freitas, Vasco; Pinto, Manuel; Guimarães, AnaA eficiência energética dos edifícios é uma preocupação comum dos países da União Europeia tendo em atenção os compromissos do protocolo de Quioto, a dependência energética da Europa e o carácter limitado dos combustíveis fosseis. Caminha-se para a limitação dos consumos de energia e para a certificação energética de todos os edifícios ou fracções. A ventilação, se por um lado constitui uma parcela significativa das perdas térmicas, no período de Inverno, o que conduz a uma necessidade de minimizar os caudais, por outro, é absolutamente necessária para assegurar caudais que garantam a qualidade do ar interior, a segurança dos utilizadores e o controlo dos riscos de condensações. A prática construtiva corrente tem evoluído no sentido de se melhorar a permeabilidade ao ar das caixilharias e da instalação de dispositivos nas cozinhas e instalações sanitárias que, muitas vezes, não garantem o número mínimo de renovações de ar necessárias. Nesta comunicação pretende-se reflectir sobre as exigências de conforto higrotérmico e sua ligação com a ventilação, bem como sobre as implicações construtivas da implementação de sistemas de ventilação natural/mistos em edifícios de habitação.
- Air permeability measurements of dwellings and building components in PortugalPublication . Pinto, Manuel; Viegas, João; Freitas, VascoVentilation represents a significant part of heat loss in winter, leading to the need to minimize airflow. However, it is absolutely necessary to ensure indoor air quality and the safety of the users and to control the risk of condensation. Ventilation is responsible on average for 30%e40% of energy consumption in air conditioning in Western European buildings. There is great variability in air change rates (ACH [h 1]) from country to country and the minimum value takes into account comfort, sensory and hygrothermal criteria. In Portugal improvements have been made in the air permeability of window frames, but despite the improvements also made in installing mechanical extraction ventilation devices in kitchens and toilets, these often do not guarantee the minimum number of air change rates required. Air permeability tests were recently carried out in five flats with identical construction characteristics, in the same building, with the aim of characterizing the air permeability of buildings and components, in Portugal. These data are particularly useful for improving the design of building components (e.g., windows and roller shutter boxes) and to perform simulations with reliable data.
- The influence of ventilation systems on domestic gas appliances: an experimental studyPublication . Pinto, Manuel; Viegas, JoãoVentilation systems play an important role in the energy consumption of heating and cooling, defining hygrothermal conditions and air quality of dwellings. Among other functions, they are absolutely necessary to ensure oxygen levels needed for household combustion appliances. In Portugal in multifamily housing and with natural ventilation systems, installing a mechanical exhaust fan in every kitchen (decentralized ventilation) is common. In this paper, the impact of such a device is evaluated regarding the performance of a water heating appliance for heating the indoor environment or for domestic hot water (B-type gas appliance usually installed in the kitchen). The combination of natural or mechanical ventilation in the kitchen with the natural exhaust of the gas appliance’s combustion products were tested as well as the evaluation of critical conditions that lead to stopping the gas appliance safely or to reversing the combustion products in the respective exhaust duct. One of the main conclusions to be drawn is that in the case of mechanical exhaust in the kitchen simultaneously with the natural exhaust of the gas appliance’s combustion products, the kitchen’s exterior air inlet is a key device for ensuring proper exhaust of combustion products. In extreme situations, reduced air intake by other means or high extraction flows, they can prevent safely stopping the appliance or even reversing the flow of the combustion products. For this purpose, the maximum flow of mechanical exhaust should also be limited.
- Ventilação Natural em Edifícios de Habitação - Caracterização dos SistemasPublication . Pinto, Manuel; Freitas, VascoAs recomendações técnicas sobre ventilação existentes em vários países propõem taxas médias de uma renovação horária nos compartimentos principais (quartos e salas) e quatro renovações por hora nos compartimentos de serviço (cozinhas e instalações sanitárias). Admite-se que estas taxas não estejam a ser satisfeitas em grande parte dos edifícios de habitação construídos recentemente em Portugal. A adopção de sistemas de “ventilação geral e permanente” é fundamental. Com o objectivo de realizar um levantamento que caracterizasse os sistemas de ventilação dos edifícios de habitação em construção na Primavera de 2000, realizou-se um inquérito que incidiu sobre um universo de 6 700 empresas do sector da Construção Civil na Região Norte, apresentando se neste artigo as principais conclusões desse estudo.
- Indoor environmental quality of classrooms in Southern European climatePublication . Almeida, Ricardo; Freitas, VascoThe indoor environmental quality within a classroom is linked to the health, comfort and performanceof students. It is well established that there are classroom environments where indoor environmentalquality is poor. Therefore, the rehabilitation of school buildings is assumed as an appropriate strategy.Consequently, some countries have sponsored nationwide programs for the rehabilitation of school build-ings, whose result has been, in some cases, other than the expected. Classrooms performance in serviceconditions must be evaluated and, from the results, optimized solutions should be established and care-fully designed and executed to have the desired effect. Thus, a research project was defined, aiming toassess the impact of retrofit on the indoor environmental quality of school buildings. The methodologyused included the in situ measurement of temperature, relative humidity, carbon dioxide concentrationand ventilation rates. A total of 24 classrooms of 9 school buildings (2 non-retrofitted and 7 recentlyretrofitted) were studied. A long term monitoring was defined with three measurement campaigns:winter, mid-season and summer conditions, each with three weeks length. The results confirmed thatnon-retrofitted schools need to improve their indoor environmental conditions and in retrofitted build-ings mechanical ventilation systems are not being used, with important consequences on the indoor airquality.
- Reabilitação de edifícios escolares: avaliação do desempenho higrotérmico em serviço e exigências regulamentaresPublication . Freitas, Vasco Peixoto de; Almeida, Ricardo