BANGOR, Maine — Six years after first planning and proposing the idea to build a large condominium building on the Fern Street site formerly occupied by New Franklin Laundry, Bob and Suzanne Kelly are close to building.

But instead of 15 condominiums, the Kellys have ripped up the old blueprint and drawn up a new one for six energy-efficient houses.

The Kellys, a husband-and-wife team that owns and operates House Revivers and Kelly Realty Management, are excited about seeing their plan finally start to take shape. They may see groundbreaking as early as late summer.

“We’ve been working on construction and insulation details, and now we’re working on floor plans,” said Bob Kelly. “About 60 percent done, and I’d like to start building the first building by September and have it done by early spring.”

The net-zero-energy houses, which essentially produce or save as much energy as they consume, would use air-to-air heat pumps, which double as air-conditioning units in the summer, Kelly said.

“There’s less expense that way because you don’t have to put in a big furnace or heating system, or central AC,” said Kelly, a Lincoln native who envisions two-story houses with two or three bedrooms and two full bathrooms.

Kelly said the initial expense of building more energy-efficient homes such as these can be higher in some areas — thicker walls, sealed windows and labor costs, for instance — but the fuel and energy savings will pay for themselves eventually.

“It’s a lot more manageable and you know your costs will be a lot better controlled with less fluctuation,” he said.

“Usually we save old buildings, but in this case the building [New Franklin Laundry] is in really bad shape,” Bob Kelly said. “Originally it was supposed to be a condominium, but that was before the housing crunch. A year ago, we started thinking in terms of single-family homes, and the advantage there is we can build them one at a time as demand warrants.”

The Kellys, who own and operate 80 office and apartment rental units in Bangor, said there is already interest in the homes, especially from married couples like themselves who are eyeing retirement and want comfortable but scaled-down houses that are less expensive and easier to maintain.

Bob Kelly said the houses will be done in a Cape or bungalow style with an average price around $200,000 apiece.

David Kelly, Bob and Suzanne’s son, also is involved with the project’s planning and building. Suzanne concentrates on marketing and interior decoration aspects.

Bob Kelly says it’s gratifying to see his vision and planning work finally nearing the construction phase, and he credits the Bangor Planning Board and Bangor Savings Bank for sticking with him.

“We got approval awhile ago for the condos, and since this is considered a minor site revision, we don’t have to go through the whole process all over again,” said Kelly. “The neighbors have been very patient with us.

“I’m really excited about it. It’s been a long time getting it together.”