Mothers Out Front use the image of a green roof meadow on Chicago’s city hall in its campaign for a revised law in Cambridge. (Photo: Roofmeadow)

We cannot keep wasting opportunities to mitigate the predicted effects of climate change, as Cambridge’s city’s leaders are doing. Consequences of our climate crisis show themselves to us now and scientists tell us that the window to act against ever-worsening climate impacts is shutting, fast. A failure to act is malfeasance, so at this juncture our only question is how.

Mothers Out Front, Cambridge, has a proposal: Let’s put green roofs on our city’s rooftops.

Green roofs offer a hand-in-glove fit with Cambridge’s voracious appetite for large-scale development in our climate times. Buildings and construction are responsible for more than a third of all carbon emissions. After looking at how other American cities put gardens, meadows and farms on their rooftops, we assessed our own green roofs ordinance and found it woefully inadequate. In short, since 2012 its presence in our zoning code has led to not one green roof being created in Cambridge.

Relying on the wisdom of other cities, we set out to revise ours. We put teeth into its words so future development and significant rehab of buildings of more than 20,000 square feet in Cambridge will be required to put vegetative and/or BioSolar, a complementary blend of vegetative and solar panels, on their rooftops. Yes, mechanicals will fit there, too.

A biosolar rooftop of a private home in Seattle, also used in the Mothers Out Front campaign. (Photo: Tucker English)

Now we’re asking for your support. Here’s why: After gathering 450 signatures from voters in Cambridge, we brought our petition to revise the city’s green roofs ordinance to the city clerk. We expect it to be on the council’s agenda Dec. 7. A favorable vote will send it to the City Council’s Ordinance Committee, where passage by that committee will return it to the council for a vote, maybe early in 2021.

The time is long overdue for our city leaders to make green roofs happen. Until now the city’s vapid green roofs ordinance has sat idle. This green roofs section is nestled in zoning Article 22 about sustainable design and development. To show how proactive this article was intended to be, in part, here is its mandate: “To promote environmentally sustainable and energy-efficient design and development practices in new construction and renovation of buildings in the city [and] encourage the incorporation of specific design features that will improve the sustainability and energy-efficiency of buildings.”

Besides providing flood mitigation against intensifying storms, green roofs do a great job in conserving a building’s energy use by providing a layer of insulation. It’s a core ingredient of our city’s sustainable development goals. Native plantings on rooftops supply sorely needed urban habitats for pollinators, as they also absorb carbon dioxide. Rooftop farms and vegetable gardens’ harvests can help with our city’s increased food insecurity. Fresh produce can be given to our city’s most vulnerable residents, bolstering such programs as Cambridge’s “What’s Cooking?” for seniors and Summer Food Program that ensures healthy meals for children. Green roofs help to cool our city’s heat islands, as summer temperatures will spend more time in the 90s as years go on. By combining solar and vegetation, the panels’ efficiency increases up to 16 percent, and those panels protect plants from too much direct sunlight.

In examining Cambridge data and its map of Article 22 buildings, we came face to face with the enormous cost we’ve already paid for our inaction on green roofs – nowhere higher than in the climate-vulnerable, frontline neighborhoods of our city:

bullet-gray-smallHad a law mandating green roofs on new and highly renovated buildings been passed in 2012 (instead of our dormant one), we would have an estimated 1.8 million square feet of green roof space on a total of 68 buildings in Cambridge.

bullet-gray-smallWe’d be benefiting from these green roofs primarily in three areas of Cambridge where climate mitigation and resiliency are most needed: East Cambridge (17 buildings, 541,448 square feet of green roofs); North Cambridge, primarily Alewife (17 buildings, 551,456 square feet); and The Port (eight buildings, 186,926 square feet). Estimates are based on the Cambridge GIS buildings layer base map and are likely overestimates; Peace Rising members doing analysis for Mothers Out Front did not have access to the roofs.

There are numerous practical reasons for having green roofs in Cambridge, but let’s move from our head to our heart: Our Covid-19 experiences awaken a shared need to experience Earth’s natural beauty within our city. Perhaps it shouldn’t surprise us to learn that simply seeing a green roof out of an office window brightens our mood and adds to productivity. In its 2019 urban agriculture (with input from Cambridge), the Metropolitan Area Planning Council spotlighted the social, nutritional and economic benefits of urban green spaces. In its findings, the council included a community’s capacity to nurture “a sense of resilience and empowerment.”

It’s time for us to require a “climate helping hand” from developers in Cambridge. If we let them build, we must oblige them to bolster resilience in the face of climate change. Affordable housing developers such as Capstone Communities already are including green roof spaces in present and future development, and we applaud them.

Other cities recognize the multiple benefits of green roofs. It’s why they’ve come up with ways to mandate their creation. In Cambridge, we should demand no less.


Melissa Ludtke, a member of Mothers Out Front, Cambridge, is writing “Locker Room Talk,” a social narrative history of her 1978 case against Major League Baseball involving equal access for women reporters.

Mothers Out Front expresses enormous gratitude to Peace Rising members Masha Vernik, Maritza Gallegos, Evan Mizerak and Helen Snively for the Article 22 research and mapmaking that help us to bring this story to life.

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