Abstract

ABSTRACT

Data modeling and simulation approaches for Urban Greenery System
in the context of climate change

Sareh Peyman



Buildings' construction, operation, and maintenance consume more than 40% of primary energy in most countries. Heat loss through a building's envelope makes up a large portion of the operational phase. Several materials have been developed to reduce thermal transmittance through building enclosures, despite their heavy environmental impact. Moreover, the unregulated and rapid expansion of urban environments caused many problems. Greenery systems can be a potential solution for improving, among other things, thermal demands and reducing urban heat islands. However, vegetation as a construction material is often overlooked in urban settings because of its design process and operation uncertainty. Thus, their performance should be studied in depth under different configurations and climates.
First, a data model for greenery systems based on a UML class diagram was developed using Eclipse to be integrated into an energy simulation workflow based on EnergyPlus as the dynamic building energy modeling engine. Such a data model facilitates the data storage and organization to analyze and optimize green infrastructure. Moreover, an urban energy simulation platform can incorporate such a data model and facilitate the appraisals of the green envelope within whole buildings and city integrated greenery system. The data model allowed the study of the impact of each parameter on the system's behavior regarding energy consumption. The optimization study was conducted on the parametrization of a green roof and a rooftop farm system to identify their response under variable initial conditions. An analysis of the essential parameters in the vegetation model was performed. Consequently, the Leaf Area Index( LAI), the substrate thickness, leaf surface albedo, and finally, the moisture content of the substrate layer showed the highest effect. Compared to the heritage building and a retrofitted scenario, the largest reduction in heating and cooling demand, took place in the rooftop farm scenario due to the more LAI and soil thickness resulting in more shading and insulation features of green roofs. In terms of its potential as a mitigation strategy for the urban heat island, greenery systems in urban environments reduce the ambient temperature due to the change in the surface albedo and the cooling effect caused by the evapotranspiration process. This study aimed to investigate whether the integration of green roofs affects the surface temperature, which is not influenced by microclimatic conditions, such as wind patterns and vapor pressure deficit. The results showed a possibility of a temperature drop of 6°-9° C on a hot summer day. On the other hand, integrating a green roof and a rooftop farm results in lower energy consumption. Therefore there is an annual equivalent carbon reduction because of energy conservation.
Because green roofs can reduce the energy consumption of buildings and sequester carbon in plants and substrates, they are considered effective for reducing atmospheric CO2. However, a green roof's components (substrate, waterproofing membrane, etc.) may produce CO2 during their lifetime. The annual amount of CO2 emitted during the production of a modular green roof and rooftop farm systems were found to be 723.6 t CO2 and 1575.76 t CO2 respectively. In the green roof and rooftop farming scenarios, annual CO2 reduction due to saved energy and CO2 reduction were 155.53 and 349.6 t CO2 respectively. Therefore the CO2 payback time of the extensive green roof and rooftop farming were between 4 and 6 years, which indicates that green roofs contribute to CO2 reduction within their lifespan. The same happened to the initial investment in green roofs assembly implementation. The cost could be paid back by the annual cost saving on energy consumption reduction which were 11 years for the extensive green roof and 23 years for the rooftop farming.
Research shows that a greenery system can replace artificial insulating materials as a passive alternative for reducing energy demands in buildings. A decrease in the ambient temperature and a reduction in the negative impacts associated with the urban heat island effect can also be achieved based on the surface temperature findings.