Communities including Boston, Cambridge and Somerville are asking developers to think about extreme heat and flooding defense strategies in the age of climate crisis.
The summer of 2021’s record-breaking heat and precipitation in Greater Boston is adding urgency to additional requirements for commercial buildings and development sites and designs that can withstand expected extreme weather in coming years.
Innovations such as reflective roofs and absorbent landscapes are becoming more common as local communities debate the responsibilities of developers to mitigate climate change.
“When you look around Boston, there’s not a lot of green space outside of the historic parks. And when you look at the new developments, there’s not a lot of vegetation,” said Blake Jackson, sustainability design leader for Stantec in Boston. “Vegetation and natural systems will always be superior to man-made systems.”
The city of Boston now asks developers of surplus, city-owned properties to think beyond traditional designs, with the goal of reducing the effects of extreme heat and intense precipitation. Contenders to lease and develop parcel R-1, a city-owned parking lot in Chinatown, are asked to include reflective building and paving materials and maximize pervious areas to absorb flood waters
Mayoral candidate and at-large City Councilor Michelle Wu wants the city to take it a step further, with new requirements and incentives for all property owners. As part of her Green New Deal environmental platform, Wu proposes a stormwater fee based upon the amount of impervious surfaces on a property, with the proceeds going into an enterprise fund to pay for district-wide stormwater defenses.
The proposal builds on strategies in places such as Philadelphia, where a decade-old city program has created more than 1,500 acres of absorbent green space to reduce stormwater, and China’s “Sponge City” initiative, which seeks to harvest and reuse rainwater in dozens of urban centers.
In Philadelphia, commercial landlords are assessed a fee based upon the amount of impervious surfaces on their property and qualify for municipal grants for stormwater reduction projects.
Suburbs Up Scrutiny
Boston’s neighbors are also taking a new look a climate resiliency requirements in new developments. Cambridge city councilors approved an ordinance in May that requires new buildings spanning at least 25,000 square feet to include vegetated material, solar arrays or a combination of the two.
And Somerville updated its sustainable and resilient buildings questionnaire last month, which seeks details on plans to attain carbon neutrality, protect building occupants from extreme heat, and keep buildings operational during major storms.
The document does not include formal requirements but can be used by the city Planning Board to impose conditions during the approval process, said Oliver Sellers-Garcia, Somerville’s director of sustainability and environment.
“You can’t really predict what climate is going to do, but it’s important to verify that climate resiliency gets picked up into the fundamental thinking because it’s the underpinning of what the community and planning board is looking for,” he said.
Some developers in Boston are starting to voluntarily include stormwater reduction in new projects. In Dorchester, Nordblom Co. has removed portions of former parking lots to create flood-absorbent and heat-reducing green spaces at The Beat, its conversion of the former Boston Globe headquarters into a 695,000-square-foot mixed-use complex, Stantec’s Jackson noted.
Designs for a 177-unit multifamily development at the city-owned Crescent parcel in Nubian Square include stormwater-retaining green roofs that will double as a heat-reducing shield, according to developers Trinity Financial and Madison Park Development Corp. Image courtesy of DHK Architects and Stantec Inc.
New Look at Cooling Capacity
June 2021 brought nine days with temperatures topping 90 degrees in Boston, a potential harbinger of summers to come. Developers are asking questions about the need to design commercial buildings’ utility capacity for increasing heat, said Chris Schaffner, CEO of Concord-based sustainability consultants The Green Engineer. Typically, that could mean the ability to cool a building at full occupancy on a 91-degree day.
“That’s always a topic of conversation and we’ve run the calculations,” Schaffner said. “What happens instead if it’s 95 degrees on a typical summer day in Boston?”
Boston could experience 40 days of over-90 degree temperatures by 2030, according to the city’s Climate Ready Boston report.
Green roofs or those made of reflective materials have become prevalent in new developments even before requirements such as Cambridge’s, Stantec’s Jackson said. The LEED building rating system gives developers an incentive to earn points for climate-conscious roof designs, Jackson said, while sometimes incorporating popular tenant amenities such as outdoor terraces.
“It prolongs the lifespan of the roof, it’s providing some additional cooling for the microclimate, it mitigates stormwater and it’s adding value to the building,” Jackson said. “Developers get blindsided by the cost of green roofs, but there’s a value there and you can create one-of-a-kind buildings.”
Studies estimate the upfront costs of green roofs at roughly three times that of a traditional design, Jackson said.
Retaining Elevated Infrastructure to Throw Shade
Climate change has prompted some land-use experts to suggest the benefits of retaining elevated roadways such as Somerville’s McGrath Highway. The city and Massachusetts Department of Transportation have been studying replacing the overpass with a surface-level artery, removing a barrier between the Union Square and Inner Belt neighborhoods.
Steve Adams
But an Urban Land Institute study in 2019 highlighted the benefits of retaining the overpass for vehicular traffic while using the shaded space below for pedestrians and community use. Ink Block owners National Development have activated an 8-acre space below Interstate 93 next to their South End development for arts, fitness and food festivals in recent years.
“When you look at the traditional forms of architecture in hotter environments, you have lots of colonnades and covered walkways,” said Scott Pollack, a principal at Boston-based architects Arrowstreet and participant in the ULI study. “We live in New England where we haven’t traditionally had to do that, but with the heat island effect, creating places where you’re not heating the surfaces becomes important.”
The so-called “Ground McGrath” project is currently in the 25 percent design phase by MassDOT.
“In a place like Somerville that has so little tree cover and is so covered in hard surfaces, are we really going to throw out a [shaded] area? It’s in the middle of a growing neighborhood, the Green Line Extension is coming in, so we could use a piece of infrastructure to build things underneath it such as parks to hang out in and bike paths,” Pollack said.
