Since moving to Capitol Hill more than 20 years ago, Dan Mattausch has developed an unusual area of expertise, one that keeps his home ablaze.

Mattausch, 46, is one of the nation’s few experts on historic lighting, and his home, named the Cortelyou House after one of its early owners, is accordingly lit with gaslight.

The house, a block from the Dirksen Senate Office Building, sparked Mattausch’s interest in lighting. When he and his wife, Nancy, a Navy contractor, moved in, they found buttons on the living room wall but couldn’t figure out what they were for. After discovering they were for gaslight, Mattausch did more research on historic lighting, focusing on gaslight specifically, and was soon one of the most knowledgeable people on the subject. He has put that knowledge to use in famous buildings, museums, movies and demonstrations.

“I’m one of the few people that can light fires in public buildings without getting in trouble,” he noted last week.

The couple restored the five-bedroom Cortelyou House to its original splendor with luxurious rugs and serene paintings, as well as antique lighting. Coming through its front door is akin to stepping into a time machine. Mattausch said the home has become a labor of love.

“I like to say I don’t know if I own the house or it owns me,” he said, laughing.

Mattausch, a Seattle native, moved to the District in 1986 to pursue an advanced degree and work in politics. Yet he hasn’t finished his dissertation in American government or worked in politics; instead, he has become entirely engrossed in antique lighting.

From 2000 to 2001, Mattausch served as president of the International Association of Collectors and Students of Historic Lighting, better known as the Rushlight Club. Current President Don Schoenly, who lives in the western Chicago suburbs, said that the club has more than 300 members but that fewer than 10 of them do the kind of restoring and consulting that Mattausch does. Mattausch has taken a significant role in every facet of the club’s activities, from leading the club to writing for its quarterly publication and developing a DVD of the publications going back to when the club was formed in the early 1930s. Most members see historic lighting only as a hobby.

“Our mission is to study, learn, share information about historic lighting,” Schoenly said.

Being one of the country’s few experts in antique lighting has its perks. Mattausch has helped restore lighting fixtures in some of the most recognizable buildings in the world, including the White House and the Capitol. He has consulted on movies such as Steven Spielberg’s 1997 drama “Amistad,” the 2003 Civil War film “Gods and Generals” and Oprah Winfrey’s 2005 TV special “Their Eyes Were Watching God.” He served a Capitol Historical Society fellowship in the curator’s office of the Architect of the Capitol, and since 2007 he has helped with the lighting collection at the Smithsonian’s National Museum of American History, a collection he says is the largest in the nation. Though the Smithsonian collection hasn’t seen the light of day for decades, Mattausch is working to get a gallery of the lights on the Internet in the next couple years.

Mattausch’s professional interest manifests itself in the properties that he and his wife have owned on Capitol Hill, especially since a Capitol Hill house tour convinced the couple that they didn’t need to follow the trends when they designed their home.

“What everybody else is doing, we’re probably doing the opposite,” he said, adding that they don’t have a TV and don’t follow popular culture.

In addition to the Cortelyou House, they own a home on A Street Northeast, and from the mid-1990s until recently, they owned a home on East Capitol Street. They sold the six-bedroom house to the wife of Rep. Michael McCaul (R-Texas) at the end of April for $2.63 million, about double its assessed value.

“When we bought that, the smart money said that we were crazy,” Mattausch remembered. “The fact that we didn’t condo it — we were just naive.”

Mattausch has no intentions of selling the Cortelyou House and continues to make it more gaslight-friendly and period authentic. There are a couple exceptions, however: The rustic kitchen does, indeed, have electric lighting turned on with the flip of a switch, and Mattausch is in the process of installing central air, a necessity when using gaslights, which quickly give off a lot of heat.

Bringing a home into the 21st century, if only in a couple spots, turns out to be a bright idea.