COOL COMMUNITIES: IMPROVING PEDESTRIAN THERMAL COMFORT IN WEST ALEXANDRIA

Abstract

Extreme heat is the leading cause of weather-related death in the United States, and heat-related morbidity and mortality are expected to continue to increase due to climate change. People living in cities are particularly vulnerable due to the impact of urban heat island, which has intensified over the past two decades. This project aims to answer the question of how landscape design can play a role in mitigating urban heat and improving pedestrian thermal comfort. A mixed-methods approach was used to assess the microclimate and outdoor comfort in an urban shopping center in Alexandria, Virginia. The site was evaluated through in-situ air and surface temperature measurements, a survey questionnaire, and environmental modeling with a combination of Rhino and Grasshopper (Ladybug) tools. Findings from the microclimate analysis and the questionnaire informed the design of a multi-functional heat-resilient landscape, which incorporated tree canopy, vegetated areas, bioretention gardens, shade structures, and alternative surface materials. The proposed design was then evaluated using the same modeling approach, demonstrating its potential to reduce direct solar radiation by 4 hours on average and improve outdoor thermal comfort by 4℉ on average – with “cool corridors” improved to feel at least 8℉ cooler. The project can serve as a template for how to map, analyze, and then address outdoor thermal comfort in the landscape, particularly in exposed sites like strip malls, streetscapes, or large parking lots.