Background
Investigation of the Effect of the Roof Geometry on Building Thermal Behaviour
Focusing on the Harran house, a vernacular building style of Turkey, this study compares the conical domed roof structure of the Harran house to that of a flat roof. The conical dome roof structure retains more air than a flat roof as it has a larger volume. Ultimately, this study found it keeps the interior cooler than the interior of the space with a flat roof. This means that the heat flux of the space with the flat roof is greater than that with a conical domed roof. This investigation tells us that natural ventilation, in conjunction with roof geometry, helps keep an interior space comfortable. To facilitate this, Harran houses have an opening at the top of the dome as well as a few on the base of the roof, which draws hot air out of the space. By measuring the air flow velocity through the roof openings, the energy transfer of the air can be calculated, which is significant in that it supports using a visual representation for heat transfer.
Focusing on the Harran house, a vernacular building style of Turkey, this study compares the conical domed roof structure of the Harran house to that of a flat roof. The conical dome roof structure retains more air than a flat roof as it has a larger volume. Ultimately, this study found it keeps the interior cooler than the interior of the space with a flat roof. This means that the heat flux of the space with the flat roof is greater than that with a conical domed roof. This investigation tells us that natural ventilation, in conjunction with roof geometry, helps keep an interior space comfortable. To facilitate this, Harran houses have an opening at the top of the dome as well as a few on the base of the roof, which draws hot air out of the space. By measuring the air flow velocity through the roof openings, the energy transfer of the air can be calculated, which is significant in that it supports using a visual representation for heat transfer.
Thermal stratification of an interior space. Sourced from: https://www.semanticscholar.org/paper/Numerical-and-Experimental-Study-of-Thermal-in-Li/d3ce03d11f22481d2c215bf68fbfbd352f538d97
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Measurement of Thermal Stratification in Large Single-Cell Buildings
Because of buoyancy forces, warm air rises and creates a positive temperature gradient between the floor and ceiling, in where the air temperature lower to the floor would be lower than that near the ceiling. The result of this phenomenon is known as thermal stratification. Aircraft hangers were studied because of their large volumes and their nature of being a single-cell building. This study found that warm stratified air located directly below the ceiling acts as an insulating buffer, which suggests that the stratification effect can reduce the cooling load of a space. This phenomenon can be affected by fans and natural ventilation. This study aimed to determine the extents of thermal stratification within a space and to understand the factors that affect this phenomenon. As such, the results suggest that ceiling height does not greatly impact thermal stratification. |
Fundamentals of Heat and Mass Transfer
The heat transfer principle that exists in relation to the ventilation of a building or interior space is convection. This process occurs between a surface and another fluid which comes into contact with the surface. When there are two different temperatures present, a density difference is created. This density difference results in a buoyant force which causes hot, less dense air to rise, and cooler denser air to sink. When this phenomenon is present, which is the situation observed within a building or interior space, natural, or free convection, occurs. Convective heat transfer can be influenced by fluid properties such as density and thermal properties, as well as flow velocity and surface geometry. Fluctuations in temperature may result in the variation of convective heat transfer. This energy flow occurs via conduction at the surface, otherwise known as the boundary layer, and is the result of a fluid coming into contact with that surface. Due to thermal variations of these boundary layers, a stratification and temperature gradient can be realized. |
Diagram of convection heat transfer. Sourced from: https://energyeducation.ca/encyclopedia/Convection
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Vernacular and Bioclimatic Architecture and Indoor Thermal Comfort Implications in Hot-Humid Climates: An Overview
Development in rapidly developing countries is uniquely positioned to adopt vernacular and passive bioclimatic strategies to support sustainable growth. Adopting this approach has the potential for architectural forms to aid in reducing energy consumption. These results were confirmed in a case study of a healthcare facility in Mozambique, which has a hot-humid climate. This study investigated the relationship vernacular materials and passive strategies have in increasing interior thermal comfort. The results of this study demonstrated that interior thermal comfort is increased by utilizing a natural ventilation system and causes a decrease in energy consumption. This suggests that using a natural ventilation system is an effective way to reduce energy consumption while simultaneously improving interior thermal comfort of spaces located in hot-humid climates. This ultimately necessitates the need for an understanding of these vernacular passive strategies and their subsequent implications.
Development in rapidly developing countries is uniquely positioned to adopt vernacular and passive bioclimatic strategies to support sustainable growth. Adopting this approach has the potential for architectural forms to aid in reducing energy consumption. These results were confirmed in a case study of a healthcare facility in Mozambique, which has a hot-humid climate. This study investigated the relationship vernacular materials and passive strategies have in increasing interior thermal comfort. The results of this study demonstrated that interior thermal comfort is increased by utilizing a natural ventilation system and causes a decrease in energy consumption. This suggests that using a natural ventilation system is an effective way to reduce energy consumption while simultaneously improving interior thermal comfort of spaces located in hot-humid climates. This ultimately necessitates the need for an understanding of these vernacular passive strategies and their subsequent implications.
Tropical-Humid Architecture in Natural Ventilation Efficient Point of View
Indonesia has a distinct vernacular architecture defined by the shape of a dwelling’s roof, thus dominating the physical appearance of the dwellings. They can be categorized into two groups based on the roof geometry: kampung, with two aslant roofs, and limasan/joglo, with four aslant roofs that typically have a high attic volume. These pointed roofs, in conjunction with openings in the walls, work together to increase interior air circulation crucial for interior thermal comfort. Due to the high humidity levels in hot-humid climates, increasing air velocity helps cool a space, however, too much air velocity can negatively impact occupant comfort. Natural ventilation can aid in this, with hot air movement vertically and cross ventilation horizontally both as useful tools. As this study states, “to face [the] climate problem, architectural parameters such as building orientation, window opening, roof shape, building performance and vegetation planning must be considered seriously” (Prianto 2000). The form of these vernacular buildings respond to this, suggesting that vernacular architecture responds to bioclimatic concerns. This forms a relationship between physical form and climatic conditions. |
Graphic of Indonesia vernacular architecture. Sourced from: https://www.semanticscholar.org/paper/The-Architectural-Structure-of-Joglo-House-as-the-Widayati-Rakhmawati/21e915b46c5f7ad955c2a5dc54852af491296d4d
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Sources
Beccali, M., V. Strazzeri, M. L. Germanà, V. Melluso, and A. Galatioto. 2018. “Vernacular and Bioclimatic Architecture and Indoor
Thermal Comfort Implications in Hot-Humid Climates: An Overview.” Renewable and Sustainable Energy Reviews 82 (February): 1726–36. https://doi.org/10.1016/j.rser.2017.06.062.
Kothandaraman, C.P. 2006. Fundamentals of Heat and Mass Transfer. Daryaganj, INDIA: New Age International Ltd. http://ebookcentral.proquest.com/lib/uncc-ebooks/detail.action?docID=424088.
Prianto, Eddy, Frédéric Bonneaud, P. Depecker, and J.P. Peneau. 2000. “Tropical-Humid Architecture in Natural Ventilation Efficient Point of View-a Reference of Traditional Architecture in Indonesia.” International Journal on Architecture Science, Hong Kong 1 (January): 80–95.
Saïd, M. N. A., R. A. MacDonald, and G. C. Durrant. 1996. “Measurement of Thermal Stratification in Large Single-Cell Buildings.” Energy and Buildings 24 (2): 105–15. https://doi.org/10.1016/0378-7788(95)00966-3.
Yıldırım, Erdal, Zeynel Firatoglu, and Bülent Yeşilata. 2017. “ÇATI GEOMETRİSİN BİNA ISIL DAVRANIŞI ÜZERİNDEKİ ETKİSİNİN İNCELENMESİ.” Uludağ University Journal of The Faculty of Engineering 22 (December): 187–200. https://doi.org/10.17482/uumfd.330923.
Thermal Comfort Implications in Hot-Humid Climates: An Overview.” Renewable and Sustainable Energy Reviews 82 (February): 1726–36. https://doi.org/10.1016/j.rser.2017.06.062.
Kothandaraman, C.P. 2006. Fundamentals of Heat and Mass Transfer. Daryaganj, INDIA: New Age International Ltd. http://ebookcentral.proquest.com/lib/uncc-ebooks/detail.action?docID=424088.
Prianto, Eddy, Frédéric Bonneaud, P. Depecker, and J.P. Peneau. 2000. “Tropical-Humid Architecture in Natural Ventilation Efficient Point of View-a Reference of Traditional Architecture in Indonesia.” International Journal on Architecture Science, Hong Kong 1 (January): 80–95.
Saïd, M. N. A., R. A. MacDonald, and G. C. Durrant. 1996. “Measurement of Thermal Stratification in Large Single-Cell Buildings.” Energy and Buildings 24 (2): 105–15. https://doi.org/10.1016/0378-7788(95)00966-3.
Yıldırım, Erdal, Zeynel Firatoglu, and Bülent Yeşilata. 2017. “ÇATI GEOMETRİSİN BİNA ISIL DAVRANIŞI ÜZERİNDEKİ ETKİSİNİN İNCELENMESİ.” Uludağ University Journal of The Faculty of Engineering 22 (December): 187–200. https://doi.org/10.17482/uumfd.330923.