By SARI KRIEGER
For home buyers, green is fast becoming a priority-whether it's because they want to reduce their energy costs, minimize their carbon footprint or improve indoor air quality.

Here are 10 questions that prospective buyers or renters ought to ask to find out how green a house or apartment is.

1. How big is it?
The bigger the home, the more energy it uses. The U.S. Green Building Council considers a "neutral size" home-basically what most people need, without what might be considered luxury space-to be 900 square feet for a one-bedroom home, 1,400 square feet for two bedrooms and 1,900 square feet for three bedrooms. A 100% increase in the size of the home adds anywhere from 15% to 50% to energy use.

2. Where is it located?
Can you walk to public transportation? Are there sidewalks or easy places to walk in the neighborhood, so you don't always have to drive? How close are shopping centers and other places you would frequent? The Web site walkscore.com rates the walkability of cities, neighborhoods and individual addresses and shows the distances to stores, restaurants, schools and amusements.

3. How is it oriented?
South-facing windows can trim heating costs in the winter. Shading from trees to the south and west can reduce cooling costs in the summer.

4. Is it well insulated, and are doors and windows sealed tightly against air leaks?
The U.S. Energy Star Web site, energystar.gov, features a calculator to help determine how much insulation you need, based on your location. To guard against air leaks, windows and exterior doors ideally should have an Energy Star rating, which indicates they meet a certain standard of efficiency in preventing the loss of heat in the winter and cooling in the summer. You may be able to feel air leaks, or you can hire an energy auditor to conduct a "door blower test"-a big fan placed in a doorway sucks air out of the home, creating easily detectable drafts rushing in from outside wherever there's a leak.

5. Has the indoor air quality been tested?
Well-insulated, well-sealed homes not only hold in heat and cooling, but also can retain toxins such as formaldehyde, mold, asbestos and lead. A test will show whether any toxins are present in levels that exceed the safe maximums established by the Environmental Protection Agency. You might also ask whether the home was constructed or renovated with nontoxic building materials and furnishings, like low- and zero-emission paints and sealants and materials like strawboard for the subflooring.

6. If it's an older home, have insulation, heating and cooling systems and appliances been upgraded?
Newer products are far more efficient than those bought several years ago. Also, has higher-efficiency lighting been installed?

7. How efficient is the water usage?
Are the kitchen and bathrooms equipped with water-efficient plumbing fixtures? If it's a house, does it have a water-conserving irrigation system for the grounds, and landscaping that minimizes the use of water? It may also have a rainwater collection and storage system, particularly in drier areas where water is increasingly scarce and costly.

8. What's on the roof?
A lighter-colored roof reflects more heat than a dark-colored roof, which absorbs heat, putting more strain on the cooling system. Does it have skylights that let in natural light?

9. Where do the home's materials come from?
Recycled or salvaged building materials reduce the home's impact on the environment. Also preferable are materials that are locally available, can be processed with less energy and water, are reusable or recyclable, are durable, and are abundant in the environment.

10. Has it been certified green?
The U.S. Green Building Council, the Environmental Protection Agency and others offer ratings on homes, based on inspections by trained third-party professionals.

- Ms. Krieger is a reporter for Dow Jones Clean Technology Insight in New York. She can be reached at sari.krieger@dowjones.com.

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