Adaptation Strategies for Urban Heat Islands & Multifamily Buildings  
Session Recap: Tuesday, Sept. 26, 2023 

Extreme heat events are becoming more frequent and more severe, increasing the occurrence of heat-related illness and death. Much of this risk is attributed to overheating in multifamily dwellings, particularly in neighborhoods with abundant asphalt, few trees, and limited financial resources.

In the Greenbuild session “Adaptation Strategies for Urban Heat Islands & Multifamily Buildings,” speakers Melissa Deas, Chief Resilience Officer for the District of Columbia Homeland Security and Emergency Management Agency, and Michael Fowler, Sustainability Integration Leader for Mithun, discuss peer-reviewed research incorporating the extreme heat data recorded from the June 2021 Pacific Northwest heatwave.

Deas went into depth on a key climate adaption initiative, Keep It Cool DC, which detailed how the District planned to sustainably cool the area in an attempt to reduce the heat island effect. The plan included four strategies, including:

  1. Increase access to cool spaces – this consists of improving access to shade, cool spaces, and drinking water in the hottest areas of the District.
  2. Design for heat – in a District experiencing record-breaking heat, it is likely that the problem will only remain if not get worse. Therefore, DC must design for the extreme temperatures by ensuring that all new buildings and developments decrease UHI instead of contributing to the problem.
  3. Enhance tree equity – trees are vital to health and climate resilience. The District has established goals to expand tree canopy and increase equitable access to healthy, well-maintained trees to reduce heat with tree species that are more inclined to provide shade.
  4. Keep learning – there are always new opportunities to incorporate new and innovative technologies and strategies to improve the extreme effects of heat. Involved parties must stay vigilant in learning from mistakes and adapting to these challenges.

Fowler discussed heat adaptation in existing buildings and how the strategies differ with new construction. These techniques include exterior shading and mechanical ventilation. If air conditioning is available, incorporating heat pumps is an alternative way to reduce energy consumption.

The session concluded with an examination of heat sensitivity with the Exposure Index, showing which populations are most sensitive to heat or the parts that are most exposed. It showed a strong correlation between low-income areas with the highest heat indexes. A problem that is not only specific to DC but also spans the entire country.

The main takeaways from the session include what lessons they learned from heat modeling, including:

  • Trees are the big winner – during the hottest time of day, trees reduce heat from 5-12 degrees.
  • Model data does have limitations – a 24-hour time period may distort results.
  • Density and heat can coexist.
  • Building efficiency goals also matter – cool and green roofs may not have big impacts on HUI but do help with efficiency.
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