Mark Turner and Nick Cioffi don’t consider themselves to be tree-hugging sort of guys.

They’re construction men, more comfortable wielding a tool belt than staging a protest to save the planet.

But they are focused on going green — and want to prove that anybody can do their part in reducing carbon emissions by turning a once-dilapidated Capitol Hill rowhouse (built in the mid-19th century, no less) into what they say will be the first carbon-neutral house in the District of Columbia.

“We wanted to show people that, heck, if you can do it to a pre-Civil War house blocks from the Capitol, you can do it to any structure,— Turner said. “We wanted a tough project to prove a point.—

Turner and Cioffi run GreenSpur, a Falls Church, Va.-based construction firm that designs and creates eco-friendly structures. They spent much of 2008 partnering with real estate developer West Group to build a 3,800-square-foot house, also carbon neutral, in McLean, Va.

Their next project, a rowhouse located just off East Capitol Street on Fourth Street Northeast, is the opposite of that project in many ways. Rather than build a big new house in the suburbs, they wanted to show they could take a smaller, historical home in the city and use smart design and construction techniques to make it carbon neutral.

And boy, is this project a doozie.

It requires a lot of work, after all, to take a more than 150-year-old home and not only make it carbon neutral, but livable for people in the 21st century.

Forget about adding energy-efficient appliances. Before tackling anything, they had to create more space.

The house’s original size measured only about 1,000 square feet. By the time construction is complete, it will be at least 2,400 square feet, said Cioffi, GreenSpur’s director of construction.

Finding that space wasn’t easy, either. Because of the home’s location in a historical district, there were restrictions about what they could do construction-wise. They were able to add a third-story office space, but that wasn’t enough room.

[IMGCAP(1)]So they had to think outside the box. They decided to dig, taking a tiny crawl space underneath the house and creating enough space for a studio basement apartment. The big dig took several months, the team filled 20 large trash containers with dirt — mostly by hand.

“We got down there with shovels and pickaxes and literally dug out the basement,— Cioffi said.

With expansion complete, they could focus on achieving carbon neutrality. They completely gutted the inside of the house (it looked more like an old barn inside than a rowhouse, Cioffi recalled) and installed eco-friendly insulation materials.

The goal: create an extremely tight building envelope.

“People talk about a green building, solar panels and all that stuff,— said Turner, GreenSpur’s founder and president. “None of it means anything if you don’t have proper insulation.—

Crews are also installing a geothermal energy system, which uses a special pump to gather air from several feet below ground to heat and cool the home. So the system always cools or heats the house with 50 degree air (even if it’s 90 or 20 degrees outside), which takes a lot less energy than a typical system.

They also colored the roof white to reflect the heat away from the building and installed large windows at the back of the house to provide plenty of natural sunlight. And the house will be filled with tankless water heaters, LED lights and Energy Star appliances.

When it’s complete, Cioffi estimates the house will produce 60 percent to 80 percent less energy compared to a typical Capitol Hill residence.

But that won’t make the home completely carbon neutral.

To achieve neutrality, they will need to buy “clean— power from the local utility company, Cioffi said, admitting that doing so is somewhat controversial in the greening community.

Some environmentalists (and greening skeptics) view buying clean power as “greenwashing,— since the house will not provide its own energy. But the pair argued that in a tight city setting such as this, becoming completely carbon neutral without buying energy elsewhere is impossible.

You can’t just install a wind turbine in the backyard, after all.

“If this were a perfect world, it would be off the grid,— Cioffi said. “Right now, it’s the only way to do it in the urban core.—

Crews are expected to wrap up the project in about two months, Turner said. The finished product will be two units: a three-story rowhouse — which will include a living room, kitchen, master suite and office space — and the studio basement apartment.

But nobody will move in, at least not right away. The team wants to use the home as a showcase for others who want to learn how to create carbon-friendly structures, Cioffi said.

No Greenpeace membership is necessary. “I’ve been a Republican all my life. We’re not tree huggers, per se,— Turner said. “All we want to do is tell the story. … We took a pre-Civil War house and made it carbon neutral.—