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Testing Outdoor Thermal Comfort Workflows for Evaluating Urban Infill Design Options
Abstract
This study tested a simulation workflow and evaluated design options for urban scale infill developments using environmental simulation tools. Options were evaluated for pedestrian thermal comfort in several design options for a tower in the park development in Toronto, Canada. Using Ladybug, ENVI-met, and Dragonfly, this simulation based-study compared existing, proposed, and optimized development options optimized for outdoor thermal comfortability. An agent-based simulation in Houdini was also used to consider how people might actually react and move in response to different zones of comfortability on the site. The study found that the preferred building massing on this site is either a podium high-rise or a mid-rise building with the highest density placed around the perimeter of a site. Testing both simulation workflows found that the Ladybug option is quicker and easier to use, making it more suitable for early stage design evaluation rather than ENVI-met. Future work should incorporate agent-based simulation in more detail, as it is only briefly explored as part of the workflows in this short paper.KeywordsThermal comfortSimulationEarly-stage design toolUniversal thermal climate index (UTCI)
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Considering climate change, controlling outdoor microclimates is an increasingly pressing concern. Microclimates have a significant effect on both outdoor and indoor comfort, and on the energy efficiency of buildings. This concern is particularly important as current climate conditions reveal that warmer summers are threatening the comfort of pedestrians and causing overheating in office environments, which is consequently increasing cooling energy consumption. A further concern is that this trend now extends to Nordic latitudes.
Existing literature demonstrates how a local microclimate depends on many factors such as urban density, shape and orientation of buildings, the types of materials present, the number of green areas and anthropogenic activities. However, there is little research focusing on how reciprocal distances among tall buildings, and their relative position, affect outdoor and indoor comfort, and the associated energy consumption of buildings. This paper presents a unique and comprehensive insight into the interconnected nature of indoor and outdoor comfort via coupled simulations.
It presents a study of clusters of tall commercial buildings located in the Nordic climate of Tallinn (Estonia) with different microclimates, and shows that the differences are due to variable shadowing and reflections and different wind patterns. The results, which focus on summer conditions, show that small variations of cluster layout strongly affect the local indoor and outdoor comfort, thus highlighting the need to conduct both studies simultaneously in research aiming to increase pedestrian and indoor comfort and resource efficiency.
Over the last two decades, urban geometry has been shown to be a key determinant of the microclimatic conditions in urban areas. This study uses the Ladybug-tools, the plugins of Grasshopper3D to optimise building heights, street widths and orientation to maximise outdoor thermal comfort, represented by the diurnal average Universal Thermal Climate Index (UTCI). In the hot-arid climate of Cairo, Egypt, the optimised parameters of symmetrical and asymmetrical urban canyons are compared with the Egyptian Construction Act's design regulations. The results show a strong negative correlation between the height-to-width (H/W) ratios and the output UTCI, with R² = 0.71, and much stronger (R² = 0.91) if east-west orientations are excluded from the results, exceeding correlations previously reported for Cairo. Maximum UTCI reductions due to changing H/W and orientation approach ∼6°C. Considerable variation is shown in the strength of the correlation between UTCI and the asymmetrical H/W ratio of each flank, with R² = 0.81 for Southeast side compared to R² = 0.4 for Northwest side. Design recommendations are given urban planners based on using the optimised parameters that at least achieve a UTCI reduction benchmark that exceeds those resulting from using the regulations’ thresholds.
2600 Don Mills resubmitted in support of LPAT settlement
- J Landau