Across the United States, McMansions are out and smaller homes with higher-end features are in. Gone is demand for ornate wine cellars and special function rooms like dual master bedrooms and upscale home theaters, while first-floor master suites and “green” details are hot home-buying trends, as long as they don’t drive the price of the home way up.

Home buyers today want to maximize their usable space, reports the American Institute of Architects in its 2009 home design trends survey of 500 architecture firms, which is supported by observations from real estate brokers and agents. Several weigh in on what you can expect to see in the residential market for 2010:

1. Small is the new big. A shift toward “smaller, better-designed homes” has already occurred among home buyers, says Zach Schabot, a broker with Garman Realty in Durham, N.C. AIA Chief Economist Kermit Baker observes that home sizes “have been trending downward recently, with a significantly higher number of architects reporting demand for smaller homes this year.” Only 4 percent of survey respondents reported increases in home square footage in 2009.

2. Open floor plans are still in. “Homes with kitchens that open up to the dining room, that open to the family room are very popular,” says Valerie Torelli, founder of Torelli Realty in Orange County, Calif. Such layouts, which have come into vogue in the last decade, are especially trendy with home buyers who enjoy entertaining guests at home; another trend impacted by the economy. Instead of expensive dinners out, more homeowners are inviting friends and family in, creating demand for living spaces that support that.

3. Dual home offices. Thanks to two-income couples in which both individuals work from home, there has been a rise in demand for extra office space. In metro New York, buyers now want a second bedroom large enough to accommodate two work stations, or a three-bedroom condo or co-op, reports Anne Buckley, an agent with Fillmore Real Estate in Brooklyn. In that case, she explains, “although the couple has no children, they desire three bedrooms because they work from home.”

4. “Green” details. Interest in affordable, eco-friendly home details is increasing, especially among younger home buyers. Some of the features Schabot has heard buyers ask for include concrete counter tops; tankless water heaters; and recycling bins built into kitchen cabinets. Energy-efficiency is another, related feature buyers are looking for, according to the AIA report. Alternative home insulation techniques and extra insulation in the attic are among most-wanted features.

5. Extending the indoors outside. According to the AIA’s report, buyers now want to make full use of their living space, including outdoor areas. That means outdoor living enhancements such as fire pits, kitchens and, in some cases, sleeping accommodations are especially desirable, allowing buyers to enjoy as much of their property as possible.

Buyers today are less willing than before to risk investing their finances in a massive home that may not appreciate as quickly as in years past. Instead, they want fully functional space that is well-designed, less expensive to maintain, and that matches how they live now — which is clearly different than how they were living even a year ago.