Abstract
Natural ventilation is an essential component in sustainable building design. However, successfully incorporating it remains difficult because the utilizable amounts of ambient energy resources differ according to project conditions such as ambient climates. Moreover, lack of a metric that could encourage an architect to design a proper plan and façade for natural ventilation at the schematic design stage is being recognized as a barrier to successful achievement of natural ventilation. An inappropriate plan and façade would make it impossible to make thorough considerations for successful implementation of natural ventilation at the later design stages. To encourage even the architects without special expertise in natural ventilation, the metric should be as simple as possible to evaluate the achieved natural ventilation design intuitively and rationally. This paper proposes net Thermal Autonomy as a modified metric of Thermal Autonomy, which cannot easily evaluate the achievement level because the applied weather data significantly influence the calculated value. In the proposed metric, a universal threshold covering climate factors is available by applying net time, while the outdoor condition suitable for natural ventilation is used in the denominator. The practicality of the proposed metric is examined through parametric building energy simulations and analyses.
Highlights
Architectural design needs to consider regional architectural characteristics in order to realize highly effective utilization of natural energy in pursuit of maximized building energy and environmental performance
A practical metric for evaluating the level of natural ventilation design achievement, analogous to the Daylight Autonomy (DA) metric employed in Leadership in Energy & Environmental Design (LEED) to evaluate the level of daylight design achievement, is necessary in architectural sustainable building design
On the premise that detailed natural ventilation designs should be implemented in the later design stages, communication between architects and engineers in the early design stages should be facilitated with a simple metric that can guide the architects to develop proper building plans and facades for successful natural ventilation implementation
Summary
Architectural design needs to consider regional architectural characteristics in order to realize highly effective utilization of natural energy in pursuit of maximized building energy and environmental performance. PPD weighted criteria are proposed in EN 15251 [19, 20], as well as the “percentage outside the range” and “degree hours criteria” indexes, for long term evaluation of the general thermal comfort conditions These criteria effectively evaluate the achieved indoor thermal environment in naturally ventilated buildings when they are applied for natural ventilation design. Placing a clear goal in terms of building design remains difficult, while the realized thermal comfort level in naturally ventilated buildings is being actively discussed [24, 25] In this context, a metric for evaluating the level of natural design achievement, especially at the early stage of building design, is essential. An energy-consumptionbased evaluation of the energy performance of the building is still required in Building Energy Modeling for reviewing compliance with design policies at a later phase, including optimization of energy consumption compared with a baseline
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