There is an urgent need for adequate natural ventilation in apartment dwellers in densely built regions that could improve occupants' summer thermal comfort and reduce the rapidly increasing energy demand for cooling. The aim of the research reported here was to identify natural ventilation strategies that could offer energy efficient refurbishment solutions for domestic buildings whilst maintaining thermal comfort of occupants. An urban multi-storey apartment building in the city of Athens was selected for this study, which is representative of over four-million Greek domestic buildings. Four retrofit strategies were tested with the aim of offering indoor air temperature reductions and increased ventilation rates relative to the existing single-sided ventilation strategy of the building, using computational fluid dynamics (CFD) simulations. The ventilation performance of all strategies varied with wind speed and direction due to the proposed design configurations. During buoyancy driven flows, acceptable ventilation rates for comfort could be achieved with the implementation of a wind-catcher and a dynamic façade. Under wind-driven ventilation, these strategies delivered significant increases in ventilation rate (up to 7 times) and contributed to reductions in indoor air temperatures of up to 2 o C, relative to the existing ventilation strategy. Cooling by water evaporation enhanced the cooling performance of the wind-catcher providing up to 4 o C temperature reductions. The successful performance of the proposed strategies highlights the potential significance of reducing energy consumption and improving thermal comfort.
In view of the ageing domestic building stock and increasing reliance on fossil fuels for cooling and ventilation of buildings, there is an urgent need for improved design knowledge and sustainable measures such as natural ventilation and passive cooling to mitigate climate change and future proof the built environment. This paper forms an appraisal of a range of low-energy refurbishment measures, i.e. building design alterations and passive systems, which were employed and evaluated in an apartment building in Greece. The applicability of these in domestic buildings in hot climates is assessed and their design implications evaluated. Implementation of wind-catchers, dynamic façades, and evaporative cooling had the highest ventilation and cooling potential, while improvements of the interior layout to allow for new airflow paths could provide further cooling to spaces and solutions to safety.
China's Hot Summer and Cold Winter zone with a 550 million population, accounts for 45% of China's building energy consumption; as such, building retrofits could offer substantial energy savings. This paper presents results from a dynamic thermal modelling study of a typical urban multi-storey residential building under three types of A/C operating schedules. Seven energy saving retrofit measures (external wall insulation, roof insulation, double-glazing, air infiltration control, window shading, communal staircase design and energy-efficient A/C) were evaluated, and the retrofit strategy with the highest annual energy savings and lowest thermal discomfort was identified. This retrofit strategy was subsequently evaluated for other flats (apartments) with different orientations and positions in the typical building. The annual space-conditioning energy could be reduced by 59 to 68%, depending on the flat location, orientation, and A/C operating schedule. The findings were then scaled up to estimate the potential energy savings in the city of Chongqing. Over 320 multi-storey residential buildings were represented by twelve archetypes. Space-conditioning energy consumption was reduced by up to 58% (18.8 TWh). This work provides evidence of the potential energy savings of city-scale retrofit that could aid China in reducing building energy consumption and achieving net-zero carbon emissions by 2050. Practical applicationsUsing dynamic thermal models, it was possible to explore a wide range of refurbishment options for China's highly energy-consuming HSCW zone with hot, humid summers and mild, chilly winters. The simulation models developed in this paper revealed that double-glazing with air infiltration control is the most effective retrofit measure for middle-floor flats, but for top-floor flats, roof insulation is the most effective; south-facing flats consume more high energy consumption than north-facing flats.Furthermore, high-rise buildings consumed less energy than low-rise buildings per square meter, and one-bedroom flats consume more energy than three-bedroom flats per square meter. This study also demonstrated the procedure to develop thermal comfort evaluation methods, A/C operating schedules and construction parameters from literature in this climate zone, when there were no standards or databases available. Findings offer a tangible, clear retrofit strategy which considers different A/C operating schedules, flat locations, and building archetypes. It can assist decision making by practitioners and homeowners aiming to upgrade the building stock of this climate zone which covers 3.4billion m 2 with 550million population, so as to reduce energy consumption and improve occupant comfort.
Rapidly developing economies of countries in hot climates face the risk of a significant increase in CO 2 emissions. This study developed strategies for low energy cooling and ventilation for Indian residences (LECaVIR). Ventilation and cooling techniques were developed and tested for India's four climatic zones. The analysis shows that natural ventilation is possible in typical residential buildings for about 20-40% of the year. Using an enhanced natural ventilation mode with appropriately sized openable windows and controls, the total number of hours for which natural ventilation is able to offer satisfactory conditions for occupants can be extended by a further 13 percentage points, leading to a potential reduction of 46% in the mechanical cooling hours for residences. Dynamic thermal simulation models, coupled with control software, were used to test the most promising natural ventilation strategies as part of a mixed-mode approach to ensure year-round comfort at minimal energy cost. The simulation shows that energy savings of up to 55% are possible. PRACTICE RELEVANCEThis paper demonstrates that it is possible to design and control cooling and ventilation strategies that make significant use of natural ventilation, despite hot climates. The paper contains details of innovative control algorithms that were tested using real designs for Indian residences where poor ventilation and overheating are common problems, often leading to the excessive use of inefficient, portable air-conditioning systems. Practitioners will also benefit from guidance on how to use dynamic thermal simulation coupled with control software to quantify the energy and thermal comfort performance of mixedmode ventilation and cooling strategies.
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