Ralph Orlowski/Getty Images This building in Germany was "greened up" with thermal windows and insulation, among other things.

"Green building" and "sustainable development" are the hottest terms in construction right now, but what do they mean, exactly? According to the Environmental Protection Agency Web site, green building is "the practice of creating healthier and more resource-efficient models of construction, renovation, operation, maintenance and demolition" [source: EPA]. Proponents say that green building is not only environmentally friendly, but also healthier and more cost-efficient. So what is sustainable development? The United Nations Environment Program defines it as development that ensures our use of resources and the environment but doesn't restrict their use by future generations.

For corporations, schools and hospitals, "green building" can entail anything from using waterless urinals to creating electricity. But homeowners who'd like to go green often don't have the big bucks that businesses do. There's a lot to consider, and the costs can make quite a difference in a home's budget. Homeowners can save cash by installing new energy-efficient light bulbs, but how "green" is it and how much "green" can it save? And who says what's green and what isn't?

In this article, we'll give you some tips on making your home more environmentally friendly (maybe you can start by recycling your gray water), and we'll learn about current legislation and how other countries are going green.