The sun also provides much of the heat for Gary Konkol's house in chilly Hudson, Wis.

WSJ: Green Goes Mainstream for New Homes��WSJ Mansion

One feature Mr. Konkol couldn't have: an open fireplace, because the chimney would require a hole in the thermally sealed house.

WSJ: Green Goes Mainstream for New Homes��WSJ Mansion

Mr. Konkol wouldn't say what he paid for the 1, 940-square-foot house but said the price was comparable to other custom homes.

WSJ: Green Goes Mainstream for New Homes��WSJ Mansion

Mr. Konkol's windows sit in tightly insulated frames and cost between 5% and 15% more than conventional, locally available triple-pane windows.

WSJ: Green Goes Mainstream for New Homes��WSJ Mansion

Over the winter, special triple-pane windows that capture 64% of the sun's warmth keep the house cozy even on 5-degree days so cozy that Mr. Konkol had lush indoor herbs, blooming orchids and a lemon tree.

WSJ: Green Goes Mainstream for New Homes��WSJ Mansion

The cube-shaped, two-story building is so airtight that Mr. Konkol, a 55-year-old family physician who bikes 16 miles every day to his practice, knows it is windy outside only from seeing trees moving through the window.

WSJ: Green Goes Mainstream for New Homes��WSJ Mansion