Just Sold! Even in the very best of the markets, houses built with unusual construction techniques can be a tough sell. This earth-sheltered concrete house with a grass roof in Maplewood is a major exception. It sold within six days of hitting the market, and there were three offers above the $525,000 list price, though the sale price won't be disclosed until after the closing in mid June, according to listing agent, Richard Berger of Coldwell Banker Burnet. The house is on 2.6 acres, has a sweeping solarium and state-of-the-art energy efficient features, including on-demand tankless water heater and a passive solar design.