The role of the existing buildings during changing climatic conditions is investigated to explore the relationship between warming trends and thermal zones in buildings. Zones sensitive to outside temperature changes are most critical for aging community due to varying daily as well as seasonal intensity of its thermal conditions. A combination of aging buildings and aging community is considered disastrous in warming climatic conditions due to increased external as well as increasing internal heat gains.
PROBLEM STATEMENT Dense urban environments and expanding boundaries with increased use of air conditioners in buildings are commonly studied features related to the urban climate change, provides foundation for this study on its implications for the aging community. Majority of the buildings are part of the urban area creating warmer conditions than countryside and power outage during hottest days is not very uncommon. Chicago heat wave underlines social segregation in urban planning, socio-cultural aspects of the community, and power (outage) connection in the heat related mortalities among aging community. This paper focuses on mixed-use development in dense urban environment to identify most suitable location for aging community with minimal thermal variations.
Majority of the existing buildings comply with the energy codes applicable at the time of its construction. Energy codes suggest most appropriate building envelope, lighting, and HVAC in relation to specific climatic zones identified by ASHRAE. Heating and cooling degree days primarily distinguishes climatic zones from one another which is changing at rapid rate since buildings are built, more frequently in recent years though. Building envelope; wall, roof, and glazing properties are crucial for balancing internal and external climatic conditions for reduced heating and cooling loads inside the thermal zone. However, existing buildings shows degradation of envelope thermal properties and increased infiltration rate due to cracks and leaks, which increases energy needs, particularly critical during summer months.
Building enclosures can exacerbate temperature within thermal zones and it varies per building type, shape, materials and inside activities. If 90% of the time indoor environment is occupied then such high percentage of occupancy makes the role of buildings critical, particularly for aging/elderly community. This study investigates sensitivity of outdoor temperature increase and infiltration rate on balanced thermal conditions during representative days of summer, fall, winter and spring. Increased dependency on air conditioning system in buildings to deal with warming climate not only increases building energy consumption but also adds significant amount of anthropogenic heat to the immediate environment. In particular, thermal zones on southern side are most sensitive to outdoor climatic conditions and it is hypothesized that elderly occupancy in such zones are particularly susceptible to external warming trends. Most heat related studies in the literature reports increased outdoor temperature over normal temperature however; its impact on buildings and its thermal zones is less studied for aging community, is highlighted of this paper.
METHODS AND MATERIAL This investigation is made possible by whole building energy simulation approach. This approach provides an opportunity for in-depth investigations of balanced thermal conditions on hourly basis through the year as it allows for variation in key parameters to be tested. Towards this, a hypothetical but representative experimental model of a 10-storied building is developed for ASHRAE Cold Climatic Zone 5 (represents Chicago, Heating Degree Days over 5500-7500 and Cooling Degree Days less than 2000) that follows ASHRAE 90.1 Energy Standard for Building except Low-Rise Residential Buildings (2004) as a baseline. The project follows a simplified perimeter and core type thermal zoning pattern on each floor to study sensitivity of the zone per orientation in this study. Further, these zone are categorized at three levels; lower level (floor 1), mid-level (floor 2-9), and top level (floor 10) to account for ground level conductive heat transfer and radiative roof exposure. A Typical Meteorological Year, TMY-2 (averaged for 1961-1990), weather file is used for estimation of thermal loads for this study.
Comparison Method Thermal conditions of each thermal zone will be compared at Floor Level and Building Level. In addition, to account for variation in changing climatic conditions previous comparison will be repeated using TMY-3 (averaged for 1976-2005) weather file.
The Floor Level comparison includes five thermal zones (4-perimeter and a core) and is studied for hourly temperature in relation to the outdoor temperature to understand influences of the orientation influences. The most sensitive thermal zone with highest variation and intensity is selected for the Building Level comparison. At this stage, sensitive thermal zone located at three levels is compared to understand the role of location of thermal zone in the building. These comparisons will be iterated using TMY-3 weather file to understand changes in climatic conditions and its influences on thermal conditions in the building.
RESULTS: The results of this study will be presented in three categories as well. Floor level results will show hourly thermal zone temperature comparison for North, South, East, West and Central Zone. Four representative days of summer, fall, winter and fall will be selected for hourly temperature analysis. The Building Level results will present comparative South Zone temperatures at lower, mid, and top levels. These results will be followed by comparative thermal zone temperature using TMY-3 weather file over TMY-2 weather file. The variation and intensity of thermal changes will be analyzed and discussed in relation to aging process and the role existing can play. OUTCOME: The outcome of this investigation provides insights on revitalization of existing communities and buildings in particular with special emphasis on thermally active occupancy areas. The quantified temperature data to inform preparatory actions for heat related vulnerability within existing buildings.
KEYWORDS Aging Buildings, Aging Community, Urban Climate Change
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