The objective of this study is to assess the effect of orientation, glazing proportion and aspect ratio of building zones on heat fluxes through their surfaces, under specific environmental conditions. The investigation is carried out for thermally-insulated building zones with a varying facade orientation corresponding to each cardinal point, during the winter period in the northern Greek region. For this purpose, three glazing-to-facade ratios (GR) are taken into account; along with the glazing ratio the influence of the glazing U value is also considered. Regarding the impact of the fenestration layout geometry, five different building aspect ratio profiles are examined. Thermal fluxes are assessed for two different indoor temperature settings, while the operation of the heating unit is assumed to be continuous. The transient thermal analysis with its mathematical formulation and solution are based on the thermal-network modelling approach, while the solar heat gain through glazing relies on the sunlit-pattern approach; in this way, the stricken by the solar rays glazing area is projected onto any interior surfaces to form the so called "sunlit" areas. As the orientation, glazing proportion and aspect ratio of the building zone vary, so do the sizes and shapes of the illuminated "sunlit" areas. Accordingly, the delivered into the zone direct solar energy and its diffused and ground reflected components can be determined. The adopted methodology provides a more accurate determination of solar heat gain with respect to glazing proportion and orientation as well as zone aspect ratio. With regard to surface orientation, glazing proportion and aspect ratio, computer results demonstrate the improvement of the thermal performance for a building zone with a south oriented glazing surface, as well as the deterioration for the other surface orientations; relative increases/decreases in the energy fluxes of a rectangular shaped building zone compared to a square-shaped building zone can reach up to 50%/100%.
Neste estudo, o efeito da espessura do isolamento e sua posição nas características térmicas dinâmicas das paredes de concreto é examinado numericamente. Quanto ao efeito do isolamento térmico, são estudadas nove diferentes configurações de parede. A análise é realizada para elementos de parede com uma orientação variável correspondente a cada ponto cardinal para o período de resfriamento e mais especificamente para as condições climáticas de Salónica, na Grécia, que tem a mesma classificação climática – subtropical úmido - pelo Sistema Köppen que Porto Alegre, no Rio Grande do Sul, Brasil. Além disso, as cargas de transmissão de resfriamento diurno são calculadas considerando diferentes temperaturas de projeto interno. Para os objetivos desta investigação, são consideradas três temperaturas típicas de design interno (aumentando de 24 ºC a 28 ºC, em passos de 2 ºC). Os resultados sublinham o significado da espessura e posição do isolamento para manter um ambiente interno estável com baixas flutuações de temperatura (proporção decrescente das amplitudes de temperatura da onda de calor, fator de decréscimo), bem como para mudar adequadamente os picos de temperatura ocorridos para a superfície interna (atraso de tempo de propagação de onda de calor, intervalo de tempo). Também é visto que as paredes orientadas norte e sul fornecem cargas de resfriamento mínimas em comparação com as paredes voltadas para o leste e o oeste. Além disso, à medida que a temperatura do projeto interno aumenta, as cargas de transmissão de resfriamento diminuem. O desempenho térmico de paredes de concreto isoladas é estudado usando o método de modelagem de rede térmica em condições periódicas estáveis.
The target towards carbon neutral cities emerges as a new way to mitigate the environmental pollution and the indisputable climate change, but it can also be the chance for the overall improvement of the quality of life by promoting the upgrading of the often low aesthetic quality of the urban environments.
The objective of the research is to investigate renovation strategies at the city scale that will not only reduce the energy demand, but they will also promote the improvement of the city’s aesthetics. Two different typologies of urban block forms of the Greek city are examined, and four scenarios of renovation interventions are analysed according to energy and aesthetic criteria.
The heating and cooling load demand is calculated through simulations for the four renovation scenarios which include:
The improvement of the thermal insulation of the building’s shells.
The use of phase change materials.
The construction of green roofs.
The integration of passive solar and shading systems.
The findings of the research prove that the energy interventions at the urban block scale can define the degree of efficiency in the energy performance level without compromising aesthetics, as the added value resulting from higher aesthetics is a basic criterion for the overall improvement of the quality of life.
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