A wood chip plant, special insulation and a promise to recycle the bulk of its construction waste has made the newly renovated Merrimack Valley High School the first school building in the state to earn a special environmental designation.

Since 2005, the state has allowed school districts to qualify for larger construction grants if the buildings they erect or renovate meet strict standards for air quality, efficiency and creative use of resources. Merrimack Valley is one of just 48 schools nationwide that have achieved the distinction, although several school districts hope to follow suit.

Timing was the chief reason the project worked out, said Principal Mike Jette. The district had already decided to overhaul the high school when the new grants became available. Going green, he said, was an easy decision.

"It was the right time in the right place," he said. "It just meant managing the project a little differently."

Merrimack Valley had been considering renovations since the mid-1990s. Among the district's chief concerns was the high school's electric heating system. The building was 40 years old and, although it had been well maintained, it was expensive to keep warm and unsuitable for modern educational needs.

Historically, the state has subsidized 30 to 60 percent of construction costs for building new schools or renovating existing buildings. Schools that meet efficiency standards receive an additional 3 percent in assistance.

"It doesn't sound like a lot but we're talking 3 percent of 30 million or 40 million," said Ed Murdough, who oversees building aid for the New Hampshire Department of Education. "That's a lot."

Several other schools are in the middle of renovations that will qualify them for the additional grants. Memorial Middle School in Laconia is making its outdated building more efficient. Profile High School in Bethlehem will, among other things, irrigate its athletic fields with recycled rain water. The Concord School Board, too, has pondered green building strategies as it has discussed plans to consolidate the city's elementary schools.

At Merrimack Valley, qualifying for the grant meant installing a wood chip plant to heat both the high school and the nearby middle school, recycling or reusing 94 percent of the construction waste and reducing building-wide energy use by 40 percent.

Although the novelty of the wood chips is wearing off, Jette said students remain pleased with the project.

"They think it's really cool," he said. "They're pretty proud of how the building turned out."