The Seattle City Council is poised to increase density in neighborhoods with town house zoning. Council members should send the “Town house Reform” bill (CB 120394) back to the Land Use Committee for amendments to address the lack of tree canopy in Seattle’s densest and hottest neighborhoods. The bill in its current form fails to consider the importance of trees to human health and summer cooling.

We suggest two amendments: Vertically stacking homes, which frees space for trees without sacrificing housing, and requiring the retention or planting of at least one significant tree. With these “tree-friendly” amendments, this bill could be a meaningful step toward addressing both our housing and climate crises. 

The bill increases town house density per lot from one home per 1,300 square feet to one home per 1,150 square feet. This adds housing, but we need both housing and trees. When heat waves and wildfire smoke are commonplace, neighborhoods without mature tree canopy suffer the most. Trees provide shade and filter pollution.

As Seattle Times columnist Naomi Ishisaka previously wrote, “areas with high amounts of concrete and low numbers of trees and shade are known as heat islands.” She noted that the tree canopy needed to cool heat islands is inequitably distributed, “in nearly all urban areas, the average person of color — regardless of income — lived in an area with higher heat island intensity.” The hottest and coolest parts of Seattle can differ by 23 degrees. Seattle’s multifamily residential areas, which include town houses, are already within these urban heat islands. These are our neighbors, and they deserve access to the benefits trees provide.

Without these amendments, the legislation as approved will make Seattle’s urban heat islands, most of them in low-income and Black, Indigenous and people of color (BIPOC) communities, worse off. Trees are not mentioned in the proposed bill. The blocks of treeless town house developments in Ballard and Fremont demonstrate that even our current town house codes are creating new heat islands.

Seattle’s anticipated new tree ordinance will not help, as achieving maximum development potential will continue to take precedence over tree retention. Finally, street trees help but will not be enough to provide the 30% canopy needed to mitigate urban heat. The city’s own canopy studies show that fully planting trees on streets and in parks will only provide 12%-18% canopy cover in residential zones, far short of Seattle’s 30% goal. This 30% target is the minimum canopy level experts say is needed for measurable public health benefits. 


So how may Seattle pursue increased density without turning its back on town house residents who also need access to shade and green space? 

Our first suggestion is to allow vertical stacking of row house and town house dwellings. This would essentially modify existing development rules to allow stacking a town house or row house over another dwelling. This could allow increased density while freeing up ground to retain trees or plant substantial shade trees. Many other cities allow this, as it provides more homes vertically, as opposed to the tall and narrow building with multiple staircases typical of Seattle’s town houses. In addition to freeing up space for shade trees, this design allows people who are not able to regularly use stairs to reside in multifamily zones. Increasing access to one-floor homes would be a positive statement about our community’s ability to welcome different types of housing that suits people of all abilities.

Our second suggestion is to require tree retention and planting. This is currently optional, as Seattle’s “Green Factor” does not require trees to be retained or planted. Among five benchmark examples of the proposed town house density provided by Seattle’s Office of Planning & Community Development, only one tree was retained, and 32 significant trees were removed. We suggest looking at paver-covered outdoor space currently dedicated to non-required parking or utility uses as good starting points for trees.

The time is now to pursue town house reform legislation that not only achieves more density, but also results in communities that have access to the health, cooling and beauty that the urban forest provides.