by Mona Mahadeva The New Haven independent
Some of the over 1,000 people registered for the conference.
How does environmentalism fit with the pro-housing movement’s rallying cry to “build, build, build?”
That was one of the defining questions on the opening day of YIMBYTown 2025, a three-day conference that drew more than 1,000 policymakers, advocates, and academics to the Omni Hotel.
First convened in Boulder, Colorado in 2016, YIMBYTown has become the premier conference for the growing “Yes in My Backyard” (YIMBY) movement, which argues that the nation’s housing affordability crisis can and should be solved by building more homes. These days, YIMBYs can be found on both sides of the political aisle, united by calls for loosened restrictions on new construction, zoning laws that permit higher-density builds, and initiatives to reduce our reliance on cars and car-centric infrastructure.
This year’s event, hosted by the pro-homes coalition Desegregate Connecticut, comes just months after Gov. Ned Lamont vetoed an ambitious housing bill that would have eased local zoning restrictions and curtailed municipal power to block new developments over parking requirements. (YIMBYTown attendees were asked by organizers on Sunday to record 15 – 30 second videos urging Lamont to pass a strong pro-homes bills).
Closely aligned with the abundance agenda — championed by Ezra Klein and Derek Thompson — YIMBY advocates are increasingly debating whether the call to “build, build, build” comes at the expense of environmental protections. In their book Abundance, Klein and Thompson argue that environmental reviews, first codified in the 1970s, discourage development — including for projects they view as critical for addressing the climate crisis.
In response, many progressives have criticized the abundance movement’s faith in technology as a solution to climate change, arguing that it overlooks the environmental costs of development. That critique closely parallels a sense of NIMBYism (“Not in my backyard”) that once dominated legacy preservation groups, which have tried to block housing developments for casting shadows on public parks or not meeting very high environmental standards.
At YIMBYTown 2025, advocates argued that housing development and environmentalism, rather than competing causes, can be complementary values. Following are some of the big-picture perspectives offered Sunday.
Bill McKibben: “Affordable Housing” Needs “Affordable Energy”
Bill McKibben, a famed environmentalist who co-founded the advocacy group Third Act, argued that environmentalism and YIMBYism are “the most obvious synergy.”
During a keynote speech on Sunday, he said, “I’m trying to convince the environmentalists that being in favor of things, as well as being against them, is an important part of this work.” The crowd, filled with almost 700 people, burst into applause.
McKibben argued that housing can’t be affordable unless energy costs are affordable as well: “It doesn’t do anyone any good to get into a home they can’t afford to operate.”
Relative to other countries, he said, the U.S. has made it time-consuming and labor-intense to get solar and wind power on the grid.
In Australia, where 40 percent of the grid is powered with renewables, homeowners can install solar panels within days. In Belgium, you can buy a solar panel and drape it on your balcony without special approvals. But in the U.S., continued McKibben, permitting can take months.
That’s costly for a few reasons, according to McKibben. First, solar and wind power are the cheapest ways to manufacture power on the planet, and it’s only getting cheaper as we develop more of it. Renewables are no longer an “alternative energy source,” he argued; now, they’re the “Costco” of power, not the “Whole Foods.”
Second, climate change is happening now, so the opportunity to massively deploy renewable energy “has to be seized quickly to matter.”
“Once the Arctic is melted, no one has a plan for how to refreeze it,” he pointed out.
He argued that many policy initiatives pursued by YIMBYs — such as making it easier to build solar farms — are “important” parts of environmental work. He also pointed to apps, currently being used in three states, that can help contractors get near-immediate approval for solar roof developments.
He also offered a cultural intervention. “Corn fields aren’t nature at its finest,” he said, and single-family suburban homes with large lawns aren’t the “sine qua non of success.”
“We need to adjust our aesthetics to understand the beauty” that infill developments and solar farms “represent to our world,” he urged.
Zack Subin and Davine Duerr: 5 Trees vs. 5 Acres
Subin: Dense housing reduces emissions.
Zack Subin, associate research director for the University of California-Berkeley’s Terner Center for Housing Innovation, argued that dense housing developments are critical for reducing carbon emissions.
Based on his research, the U.S. is a global outlier in terms of carbon emissions per person from vehicles and the amount of land zoned for single-family homes.
More sprawl, he argued, means “more steel and concrete” and more “forests and farmlands paved over.” His paper also points out that single-family homes, which “uniquely privilege” the “convenience of car ownership,” consume more energy and imply higher “embodied” carbon levels than multi-family houses.
Washington State Rep. Davina Duerr, who shared a panel with Subin on Sunday, added that people can’t always see the synergy between development and environmentalism.
“Sprawl is absolutely the least environmental policy that we could have,” said Duerr. In her experience, when traditional environmentalists obsess over saving the five trees in their neighborhood, they don’t realize that “those five trees could be five acres” if developers are allowed to build more density.
“I like to say that you can choose two of three: cars, trees, or homes,” said Subin.
Later on, Subin argued that contrary to what some progressives argue, YIMBYism and abundance are pursuing something more nuanced than “deregulation.” It’s more about developing regulations that prioritize “outcomes” over “process,” he explained.
He cited the California Environmental Quality Act (CEQA), so vaguely formed that an appellate court ruled that students’ “social noise” could constitute a reason to block a new housing development. (The California Supreme Court later overturned the ruling, and the state legislature amended CEQA to exclude human noise from environmental impact assessments). He contrasted CEQA with the Clean Air Act, a regulation that specifies a metric for measuring something’s environmental impact.
“Climate is a different problem,” he explained. “There are going to be environmental tradeoffs,” such as, “on the margin,” some farmlands being transformed into sites for solar panels.
He emphasized, however, not to “let the status quo get a pass.” For example, corn ethanol fields use up more land than solar panels, and also don’t reflect the preservation goals of most environmentalists.
Heather Clark: Don’t Build Build Build In “Harm’s Way”
Heather Clark, the Biden Administration’s senior director for building sector climate policy, argued that some climate regulations are needed for new construction, even with the climate benefits of dense housing.
She took part in a panel called “Plenary: Uninsurable America?,” in which speakers discussed how large swaths of the U.S. have become uninsurable due to climate risk. One study found that 25 percent of homes in the U.S. face a “severe or extreme” climate risk, and people are still moving to those areas at a “historic rate.”
Given that, Clark argued for a change to the building code, not just to “get rid of all the crap that makes it hard to build,” but also to require homes to be resilient and strong.
She also proposed mandating new builds to release “zero emissions,” which she defined at a different conference in 2023 to mean “highly energy efficient,” “free of on-site emissions from energy use,” and “powered solely from clean energy sources.” (While in office, she acknowledged the ambiguity in the term “net zero building” and spearheaded efforts to define it).
Finally, she said that houses shouldn’t be developed on “flood plains” or places at high risks of “wildfires,” arguing that it’s “not worth” building if it places people “in harm’s way.”