From the street, the house on Lake Albert Drive in Windermere, Fla., could be in any new subdivision anywhere in the United States. Its most dominant feature is a large garage door with windows painted to match the trim.

But once inside, your impression immediately changes. The home is an unusually successful melding of green construction, tasteful design, and moderate size and expense.

The KB Home GreenHouse, a concept house for the International Builders Show in Orlando, was created with taste maven Martha Stewart and her firm, Martha Stewart Living Omnimedia, and sponsored by Builder Magazine.

The house is net-zero, which means that over a year, it generates as much energy as it uses. During the day, an unusually large 8.57-kilowatt-size solar photovoltaic array on the roof generates 100 percent of the electricity required for heating and cooling as well as operating all household appliances. After the sun goes down and on cloudy days, the house draws electricity from the grid. When the house generates more electricity than is required for household activities, the excess is sent to the grid and the utility pays the owners for using it.

The house has received the U.S. Green Building Council's LEED Platinum rating, the highest in the LEED ranking system. This is unusual for a production-built house, but George Glance, KB's Orlando division president, said it was an easily done once they had achieved net-zero status on energy use.

All the features that make the house zero-energy are hidden from view, and most visitors will concentrate on the visuals, as I did.

The first thing you'll notice is size. With 2,600 square feet and four bedrooms, the house is bigger than it appears to be from the street. The second thing is the high level of natural daylight in the main living areas. And the third is that it feels just right.

Stewart is a wizard with details, scale and proportion. She did not create the design, but she modified it to great effect. In fact, her sense of these things is why KB Home brought her in on the project, Stewart said in an interview. "They had many houses with ungainly proportions, and that's why they brought us in. We are good at proportions and making smaller spaces work."

Stewart has also pushed for architectural honesty. The front of this house is intentionally unpretentious because, she said, "an unprepossessing facade is my goal. I hate McMansions. Why spend money on giant columns and eyebrow windows? I insist, no fakery!"

Stewart and her staff have been working with KB Home for five years, but this home marks a new direction for their collaboration. The house is one story, and, with 2,600 square feet, it's roughly half the size of the four houses that Stewart previously designed for KB Homes, which are based on her homes in New York, Connecticut and Maine.

Rooms in the demonstration home are much closer to the size most visitors will actually inhabit. The biggest eye-opener is the great room, which is about the same size as the combined eat-in kitchen and family room found in the typical 2,400-square-foot houses that have been a staple of American home building for the past 20 years. But Stewart's version is a dramatic improvement.

In the great room, natural light pours in from about 30 linear feet of glass in a space that's only 36 feet long and 16 feet wide. That's a lot of light, but it is used in the sitting and kitchen areas to quite different effect. The sitting area at one end has two pairs of 6-by-6-foot double-hung windows, much bigger than you would find in a typical production-built house. When you stand or sit in this well-lit space, you're definitely inside, looking out. But when you're in the kitchen or eating area, the distinction between inside and outside is not so clear. When the 8-by-16-foot sliding door is fully opened, all four glass panels slide into a pocket, making the line between indoors and outdoors disappear.

Stewart uses other devices to make this space feel comfortable. The 9-foot, 4-inch ceiling height is not unusual for a production house, but Stewart's crown moldings and trim details at the windows, doors and wall base are larger than usual and proportionally appropriate.

In keeping with her style, the look and lines of Stewart's kitchen are simple. The floor-to-ceiling open shelving and cabinets along the back wall, a signature in all her houses, are white, as is the large quantity of dishware displayed. The centerpiece of the kitchen is the 5-by-8-foot center island, large enough to prepare any dish in any quantity and only a 180-degree turn away from the stove opposite it.

The kitchen has no garbage disposal, which Stewart has never installed in any of her own houses. Instead, she specified a drop-in compost canister for vegetable and fruit waste to be installed in the counter area near the sink. When it's full, the canister, which looks like a stainless steel bucket, is pulled out and the accumulated scraps are dumped in a composting bin in the back yard. This setup is one that Stewart, an avid gardener, follows at her own houses.

The powerful range exhaust hood, which Stewart selected, has a huge motor than can eliminate 1,200 cubic feet of air per minute, enough to get rid of the smoke and smell of any cooking mishap in short order.

Noting that "most builders tend to skimp on hallway width," Stewart widened the ones here to make the rooms feel more spacious. The master suite includes a generously sized dressing area with a three-sided mirror, an unusual detail most people will appreciate.

Stewart hopes the house's visitors will take away two important ideas. It's possible at this price, $380,000, to build a house that's "environmentally appropriate for the times." And that a house this size can have privacy in the bedrooms and flexibility in the use of the main living areas.

When asked whether she had any rule of thumb for getting the proportions right, given how central they are to her own thinking, she said, "A sense of proportions is learned."

She learned them herself by careful study of "Architectural Graphic Standards," a classic reference used by almost all practicing architects and interior designers. Stewart said she purchased her own well-worn copy when she was a freshman in college and interested in architectural history, which she eventually chose as her major. Katherine Salant has an architecture degree from Harvard. A native Washingtonian, she grew up in Fairfax County and now lives in Michigan.