PORTLAND — Elissa Armstrong dragged a plastic block against wooden rectangle, tamping down a layer of adhesive. Soon, her handiwork would help warm a neighbor’s home.

For more than a decade, the nonprofit WindowDressers has offered low- or no-cost window inserts, designed to plug drafty windows and keep heat indoors. Armstrong, a longtime volunteer turned coordinator, said the Rockland-based group helps New Englanders lower their heating bills while bringing people together for “community build” sessions.

“We generally say they can last at least 10 years,” she told a group of volunteers as she demonstrated how to make one.

Armstrong helped organize a build at First Parish Church last week, inviting dozens of local volunteers to construct more than 300 inserts. For days, they packed into the church’s community room, filling the space with massive rolls of plastic wrap, pre-cut pieces of wood and a smattering of custom-built tools.

For Mainers facing ever-climbing energy bills, especially lower-income residents who are already feeling pinched, the inserts can offer real relief, said Executive Director Jessica Williams. Plus, they help cut down on overall fossil fuel usage, she said.

USING AND LOSING LESS HEAT

WindowDresessers claims each insert can save about 8.5 gallons of heating oil — the primary source of heat in about half of Maine households — each year, based on an in-house analysis conducted by a University of Maine professor in 2023.

That amounts to about $28 in annual savings per window for oil users based on the state’s current average fuel price, which can fluctuate over the season. Williams said the team has not calculated savings for users of electric heat sources like heat pumps.

Each insert consists of custom-measured wooden frames, which are wrapped in two layers of shrink wrap, leaving a pocket of still air in between. Once snugged into a window, the insert creates a second layer of air between its plastic and the glass pane. A strip of foam along the edges helps form a tight seal.

Anyone can order inserts, and the price varies based on size. For a 30″ by 52″ window, an insert typically costs about $50 or $67, depending on whether the customer wants the wood to be painted.

Those who qualify for public assistance programs like Supplemental Nutrition Assistance Program or the Low-Income Home Energy Assistance Program can get up to 10 unpainted inserts for free or at a pay-what-you-can rate.

About 39% of last year’s inserts went to low-income customers, Williams said. This year appears to have a similar ratio, but that could change as the season continues, she said. There are at least a dozen more community builds planned for this year and early 2026, according to the group’s website.

WindowDressers has distributed more than 70,000 inserts since it was founded in 2010. Last year, volunteers produced more than 10,500 inserts, up from about 10,000 in 2023, according to the organization.

“You can get these inserts for whatever you can afford to pay. The only thing that we ask is that you can participate in the build,” Williams said.

PITCHING IN

Customers are asked to work about four hours for every three to five inserts they order. The community building sessions keep the costs of labor — and, ultimately, the price of the inserts — low.

Most who volunteer are getting inserts for themselves, but some are just looking to give back to their communities, Williams said. She said the physicality of the work and the directness of its impact are major draws.

“This is something that people feel is a very concrete thing that they can do to help mitigate the causes of climate change,” Williams said. “That’s really the crux of what makes WindowDressers so incredible, is just seeing the power that volunteers can have.”

As she stretched wrinkles out of a freshly-mounted sheet of plastic, Portland resident Kate Silvers said she heard about the program a few years ago. She started just as a volunteer.

“But then I got so interested I wanted some in my house,” Silvers said. She pointed to a stack of frames a few feet away. “These are mine.”

Silvers, 67, said she and her husband, Rob Silvers, 72, burn heating oil during the coldest months and wood pellets during the shoulder seasons. They usually keep the heat on low.

“Oil is expensive, and we’re on a fixed income. So I’m hoping this should make a difference,” she said.

Throughout the week, dozens of students from King Middle School joined the volunteer crew, stopping by in small group.

Molly Knoll, 13, ran a yellow razor blade along the edge of a wooden frame to shear off excess plastic wrap. She watched closely, moving carefully to prevent tearing the sheet or cutting into the frame. Around her, classmates joked about who had the best technique.

As she left the church, Knoll said it felt good to lend a hand.

“It is helping with the future, and it costs less money. And it’s like building a better community,” Knoll said.