Aurora the cat crept over to the pet door and then disappeared. Her litter box was on the other side, concealed within a maple cabinet in her owners' Minneapolis mudroom. A moment later, a motion detector triggered a fan to ventilate the area.

This cat-friendly — and owner-friendly — feature is one of many updates and improvements Heidi Hardner and Bill Humphrey have made to their early-1900s bungalow. They added a total of 500 square feet on the main and second floors to expand the kitchen and master suite and create a handy mudroom. And they did it all with an eye on sustainability, by incorporating eco-friendly products and practices such as geothermal heating and cooling, a metal roof and recycled materials. Plus, the home's new modified shape blends with the modestly scaled homes in their Fulton neighborhood.

"We kept the home's original front porch," said Humphrey. "Even with the addition, it's still a reasonable size. And the changes on the back and sides are subtle."

The couple's remodeling project, designed by Wynne Yelland and Paul Neseth of Locus Architecture, earned the EcoBlend award last fall, a new category, added in 2012, to the seven-year-old B.L.E.N.D Awards (Buildings and Landscapes Enhancing the Neighborhood through Design). The award program is designed to encourage and recognize builders, architects and homeowners who incorporate eco-friendly design and sustainable building practices into new and remodeled projects in Minneapolis, while respecting neighborhoods' overall character.

"The idea of blending without having a house that's historically nostalgic is a big accomplishment," said Yelland. "But this project was less about a green checklist and more about how we could maximize what Bill and Heidi wanted, without adding excessive square footage, and make the envelope more efficient."

Hardner and Humphrey bought the three-bedroom house in 1997. By the time they approached Locus Architecture, they had assembled a 60-page "idea book" to show Yelland and Neseth.

"It spooked us at the beginning," Yelland admitted. "The kind of people who would make such a document would be very thorough about all the details."

The architects and homeowners agreed that they needed to put on some kind of addition to achieve an expanded kitchen and new mudroom on the main floor and a roomier and modernized bedroom and bathroom on the second floor.

"We had to shoehorn all that into a tight building space," said Yelland. The couple also requested the use of energy-efficient features wherever possible. "We wanted a contemporary aesthetic that would blend the old and new parts and also have sustainability," said Hardner.

The final design was driven by the narrow lot size and setback restrictions, as well as the couple's day-to day living requirements. On the dining room side, Yelland designed a long modern bay with windows that created space for built-in shelves and storage and a new mudroom, which could be entered from the back yard.

On the back of the home, he devised a two-story addition, rebuilding a new roofline and replacing the old asphalt with a durable metal roof that would last 50 years. "The new roofline looks neither modern or old to me," said Yelland. "It spans the two."

From the exterior, you can see the master bedroom's contemporary asymmetrical gable, which draws in light for Hardner's orchids and provides a sunny nook for their two cats. In fact, the felines influenced many of the interior's amenities.

"The pet features are really for us," said Hardner. "We don't want to see litter boxes, step in food bowls or have cats jumping into the sink to try to get a drink while we're brushing our teeth."

That's why the litter box is hidden in the mudroom cabinet, accessed by two pet doors covered with the same fabric as the nearby window seat. The dining room's whimsical maple cabinetry has multiple levels for the cats to climb. In the upstairs shower, there's a motion-activated drinking fountain.

" 'There's no good place for kitty litter' seems at least as worthy of a design solution as 'There's no room for my pots and pans' or whatever else you would hope to cure in a remodel," said Hardner.

There's also plenty of room for pots and pans, inside pull-out drawers, in the couple's transformed kitchen. The clean-lined contemporary space is anchored by a massive center island covered with PaperStone, a recycled product. Fused glass pendants by local artist Malcom Potek are suspended above. The new appliances include an induction cooktop. "We're nerds," said Hardner, noting that she and Humphrey are both physicists. "We like the idea of using new technology." And for the cats, there's a tiny door opening to the pantry where their food bowls are stored.

The couple also showcase their taste for vibrant hues throughout the home, including the kitchen, which boasts walls in two different shades of vivid teal. "We were not renting anymore, so we started to paint cheerful, bold colors," said Hardner.

"I don't think I'd feel at home in an all-white kitchen," added Humphrey.

The light-stained maple cabinets are a contrast to the dark oak woodwork in the old part at the front of the house. But the couple wished to preserve some of the handsome Craftsman architectural details from the Arts and Crafts period. They still climb the original dark oak staircase to get to the second floor. "We kept it, squeaks and all," said Hardner.

Yelland relocated the Craftsman oak buffet from the back dining-room wall to a newly built wall between the dining room and the new kitchen. "They definitely wanted to keep it," he said. "Placing it in the core of the house made the most sense."

Upstairs, Yelland opened up Humphrey's cramped home office by removing a wall and replacing it with a sliding bookcase, a look Hardner had seen in a magazine. It allows them to convert the adjacent TV room into a bedroom when they have guests.

The rear addition houses a spacious master bedroom and tropical flavored bathroom. The walk-in shower walls are a translucent aqua, and the vessel sink is as green as grass. The floor is covered with dark blue Marmoleum. "The colors keep you awake in the morning," said Humphrey.

Today the revitalized bungalow consumes much less energy, will last for many more decades and is customized for Humphrey, Hardner and their cats. The couple's favorite spot is the kitchen island, where they can relax and bathe in the natural light from the floor-length windows. Aurora and Nokomis spend a lot of their time on the new window seats.

"They love to watch birds or lounge in the sun," said Hardner. "The glass is always full of noseprints."

For more information about the B.L.E.N.D awards, go to www.blendaward.org.

Lynn Underwood • 612-673-7619"