SIZE MATTERS: When this Martha’s Vineyard mega-mansion came close to falling into the sea, the owner simply bought up the neighboring property and had it moved back. The house is among several that inspired the filmmaker to make “One Big Home,” one of the offerings at the Princeton Environmental Film Festival through this weekend at Princeton Public Library.

Thomas Bena was working as a carpenter on the idyllic island of Martha’s Vineyard when he started noticing that homes being built were getting bigger — a lot bigger. On land overlooking the ocean where modest, clapboard homes once stood, huge mansions many times their size were going up at a rapid pace. 

Mr. Bena was alarmed. An amateur filmmaker who had made short features with friends and founded the Martha’s Vineyard Film Festival 17 years ago, he decided to do a full documentary that would bring attention to what was clearly a growing trend. One Big Home, which screens at the Princeton Public Library’s Princeton Environmental Film Festival (PEFF) on Friday, March 31, is an absorbing account of a community’s effort to deal successfully with the issue of protecting character and environment while supporting the local economy.

“I had seen some of the houses my friends were working on, and I couldn’t even fathom that anyone would need a house this big,” said Mr. Bena, who has lived on Martha’s Vineyard for 19 years. “I mean, there were 20,000-square-feet houses. They are used only a few months a year if that, but they are heated all year because they have million dollar art collections and tropical hardwoods, so you can’t let the heat fluctuate that much. That’s the part that horrified me.”

Growing up in Middleboro, Massachusetts, Mr. Bena worked in the business world after graduating from the University of Massachusetts at Amherst. “But it wasn’t for me,” he recalled. “So I went traveling around. I saw so many places that had been ruined by this kind of thing. It only takes a few decades. So I was concerned.”

To do justice to One Big Home, Mr. Bena knew he had to raise money and hire professionals. The issue was contentious. On one side, there were builders making a good living from the mega-projects wiling to look the other way. On the other were longtime residents angry about changes to the landscape of their beloved island.

“The board was nervous about fundraising at first,” he said. “But this is not an anti-wealth film. It really is pro-community. We ended up selling out 10 times last summer, and people are still going to see the film. I think it was kind of like the elephant in the room, like you can’t bite the hand that feeds you. But it has been very well received.”

One Big Home follows Mr. Bena from when he first started filming on the sly at a construction site to the planning board meetings where, ultimately, a new bylaw limiting house size was voted in. Filming took years.

We watch Mr. Bena evolve as he becomes a husband and doting father. He is distinctly uncomfortable when the charming but rotted-beyond-repair house on property he and his wife acquire will have to come down. In its place, another house goes up — a microcosm of the situation to which he is so opposed.

“I talk about my own experience in the film,” he said. “My wife and I built a home that is 2,900 square feet, twice as big as the home I grew up in. That was weird for me at first.”

Smitten with family life, notably his adorable baby daughter, Mr. Bena tells the camera at one point that he is through trying to change the mega-mansion situation on the island, and is focusing instead on his own home and future. But it doesn’t take long for him to jump back into the fray. When the owner of a huge summer house close to falling into the ocean buys the neighboring property so he can roll the house back, the film crew is on hand to document the move. “That was the most outrageous thing I saw,” he said. “It wasn’t easy, but we got it.”

The film festival, which began Monday and runs through this Sunday, April 2, includes several events in addition to screenings including a single author program, poetry, a late night program for students featuring break dancers, and refreshments supplied by Small World Coffee and The Bent Spoon. Remaining screenings of films on a variety of topics about the natural world and the built environment are at the library and various locations at Princeton University. A full schedule is available at www.princetonlibrary.org.

Mr. Bena and producer/editor James Holland will be on hand to answer questions following the screening of One Big Home on Friday at 7 p.m.

“The Vineyard is like so many small places in America, where people who live and work there are being pushed out because they can’t afford to stay,” he said. “Like any good documentary film, this one doesn’t have the answers. But we have to open a dialogue. A lot of environmental films can be downers. But I really think mine is more of a positive statement that local people can protect their environment. They just have to get in there and do the work.”