Estimating her expenses to live for two years in New Haven, Conn., while a graduate student at Yale University, Elizabeth Turnbull arrived at about $14,000, even if she shared an apartment.

"Well, if I have roughly $14,000 I am going to spend on living space anyway, is there something more creative I can do with it?" she asked.

There was.

An incoming student at Yale's School of Forestry and Environmental Studies, where students fret as much about their carbon footprint as they do about grades, Turnbull decided to build her own living space. It would be tiny, transportable and ever so environmentally friendly — green as grass.

For months, she has been building it on the grounds of the Governor's Academy in Byfield, Mass., a preparatory school she attended. She works in a nearby town as a sustainability coordinator with a building company.

Her new home-to-be is 8 feet by 18 feet and was built atop a flatbed trailer. It has a tiny sleeping loft, a storage loft, a study nook, a kitchen area, a living area and a bathroom. She plans to tow it to New Haven in the early fall to a site within biking distance of the School of Forestry and Environmental Studies.

The house is so compact, she expects to light it and power her cell phone and laptop computer with the energy generated from three solar panels that total about 18 square feet of surface. That's renewable energy, totally free.

"I am really a glutton for light. I mean, I do not want to be living in a cave," she said. "I probably could have gotten away with even a smaller solar array, but it can be kind of cloudy in New Haven sometimes, and I thought that was something that I did not want to compromise on. So it will be a very well-lit space."

She'll cook her meals and heat the "Tiny House" — as she calls it — with propane. She estimates her yearly propane cost will be $200 maximum.

The house has a recyclable aluminum roof, uses recycled boat sails for ceilings, features insulation from a waste soy product and environmentally friendly paints. Many fixtures and building materials were donated by people who had lumber or hardware left over from household renovations or expansions.

"The Tiny House has taken me by the hand and led me through the process of building it," she said. "You know when you are doing something and the process takes over? Your arms are moving because the project has almost gotten inside your body and told you what to do."

Assuming it meshes with local regulations, she'll have a composting toilet that recycles human waste. The bathroom — toilet and shower stall combined — measures 3 feet by 3 1/2 feet.

So far, Turnbull has spent about $8,000 on the house and expects it to cost about $11,000 when finished and furnished.

An inspiration for her house was the Tumbleweed Tiny House Co. in Sebastopol, Calif., which sells small, transportable homes. But they cost more than she could afford.

"I thought, 'I'm working with a building company, and I have some skills. Why not try it?' "

She set to work designing her space, contacting zoning officials in New Haven and talking with companies that might sponsor her project.

Her former school agreed to let her build the house on the school grounds and gave her use of tools. Friends and volunteers have been helping her (a friend did the wiring), like an old-fashioned barn-raising. Companies donated some materials, and people have chipped in with time or furnishings.

Turnbull, who lives in Newburyport, Mass., is from Charleston, W.Va. She majored in environmental policy and economics at Colby College in Maine, worked on the West Virginia staff of 2004 presidential candidate Sen. John Kerry, D-Mass., led bicycle trips across the U.S. and Europe, worked for a natural-resources consulting company, then the federal Department of Energy and, most recently, led trips for an adventure travel company, visiting 29 countries in 14 months. She is 26, and her job this summer, besides building the Tiny House, is to help O'Neil Fine Builders incorporate green materials and practices into its projects.

Exactly where she will place the Tiny House in New Haven is not determined, but Turnbull is talking with the city and the university about sites. She is optimistic she'll find a spot that is safe and convenient.

Gordon T. Geballe, associate dean for student and alumni affairs at the School of Forestry and Environmental Studies, said Turnbull's house would be a symbolic statement but also would provide useful information on sustainable living in a small space, which he expects to become more common.

"I'm not sure everyone will live in a tiny house, but a lot of people will live in a small house. So the kinds of things she will learn will be useful to engineers and architects and homeowners. There is no reason why so-called second homes on a lake can't be something more like this than a mansion."

The School of Forestry and Environmental Studies is itself preparing to move to a new building, a 50,000-square-foot state-of-the-art green headquarters.

"We're ecstatic that one of our students is pushing the envelope here," Geballe said.

Meanwhile, Turnbull is putting the finishing touches on the Tiny House, deciding whether there is room for a futon and building cabinets. What has surprised her as the project progressed is that the space feels larger than she expected.

"You don't need a lot to live really well," Turnbull said. "I hope."