That amounts to 12 positions at the Somerville location, as well as six at its location in Houston.

In an email to Greentown’s members and supporters, CEO and president Kevin Knobloch explained that layoffs come following four years of rapid growth — aimed at growing the company’s reach and impact — that ultimately outpaced its revenue.

“Despite this decision, I remain optimistic about the future for Greentown and the impact we will have on addressing the climate crisis,” Knobloch said in the email. “Our mission is as urgent as ever and we remain committed to supporting all of you — our startups — by prioritizing core operations, member services, and strategic partner engagements.”

The incubator, established in 2011, is home to companies working on solutions that address all corners of the climate crisis, including an aerogel that can make windows 50 percent more energy efficient; lightweight and flexible solar power-generating “films” that can replace traditional solar panels; and plant-based “pork” products produced in a process akin to spinning cotton candy. Greentown Labs supports roughly 125 startups in Somerville and 68 in Houston.

Elizabeth Turnbull Henry, president of the Environmental League of Massachusetts, called the news “painful” but said it didn’t change her sense that Greentown will remain “a thriving, vibrant hub for climate-tech and a beloved home for entrepreneurs in this sector for years to come.”

There have been positive signals in the climate-tech space, including Governor Maura Healey’s proposed $1 billion, 10-year initiative to make the state a global leader in the industry. Billions of dollars have also been made available through the federal Inflation Reduction Act, aimed at boosting new and existing technologies.

But even with new public investments in the industry, it’s been a hard few years for companies in general and climate-tech is not immune, said Joseph Curtatone, president of the trade group and advocacy organization Northeast Clean Energy Council, who championed Greentown Labs as the former mayor of Somerville. Companies are “dealing with some realities — economic challenges, workforce shortages, and some of it is just rising costs,” he said.

Curtatone said he didn’t “want to minimize the impact of anyone being laid off”; but he said hard decisions such as layoffs aren’t necessarily a sign of a trouble ahead, and can instead be a part of making sure companies are able to “deliver on the mission.”

In his email, Knobloch said the layoffs “will position us well for our next chapter of growth.”

Knobloch was named chief executive last August, taking over from longtime leader Emily Reichert, who is now CEO of the Massachusetts Clean Energy Center. Knobloch had previously served as president of the Cambridge-based advocacy group Union of Concerned Scientists, and been chief of staff at the US Department of Energy prior to starting his own clean energy consulting and advisory firm.