Going green at home is a hot topic in every circle these days. Bathroom cleaners are now environmentally friendly, we're using insulation to keep heating costs down and screwing in fluorescent light bulbs to reduce electricity bills. But even with all the options for greening a home, roofs are often left out of the equation. Bill Christensen, founder of Building Green, a group based in Austin, Texas committed to providing green building information, says roofing has often been a neglected part of sustainable building, leaving open valuable space that can easily contribute to lowering costs and protecting the environment. However, that neglect appears to be changing. Ralph Velasquez, director of sustainable technology for Tremco, a sustainability focused roofing company in Beachwood, Ohio, notes a growing desire for environmentally friendly roofing products as Americans become more conscious of their environmental impact. While popular in Europe for years, the green roof concept is just starting to catch on in America, and is taking off in larger cities. In fact, a recent study for the city of Chicago completed by Chicago, Illinois based Weston Design Consultants estimates that the greening of all of the city's rooftops would produce $100,000,000 in saved energy costs. Blending modern techniques with tried-and-true methods can turn an empty roof into an environmentally sound space. Christensen and Velasquez offer their opinions on the hottest ways for roofs to go green.

1. Vegetated Roofs

The biggst movement these days is planting a garden on the roof. For individuals that are looking for an easy way to set up a vegetated roof without professional help or a lot of investment, Green Paks are the way to go. The Paks are a combination of engineered nutrient rich soil, and if you choose, are pre-seeded to fit the homeowners region. They are placed directly on your roof, opened and either simply watered or filled with plants of your choice. The product can easily cover an entire roof.

2. Perfect Plant

A movement in vegetative roofing focuses on plant selection. Original green roofs selected popular grasses and green plants without considering the area. Velasquez says his company has hired a horticulturalist to work on their green roof projects to select plants native to the region, as indigenous plants require minimal care. In addition, horticulturalists have bred grasses to make them more drought resistant, creating a perfect plant for a building owner in drier areas or who simply doesn't want the hassle of constant upkeep.

3. Rain Guards

Many green roof companies are focusing on establishing drainage and runoff containment systems on roofs, says Velasquez. Rain guards are special rubber edging that keeps rainfall on vegetated roofs in the soil and plants, instead of on the ground. Thereby preventing water from running off into the streets where it often collects filth and chemicals, dirtying the water it drains into and destroying wildlife. In fact, an extensive green roof with proper rain guards can retain half of annual rainfall. The correct engineering of a green roof saves the environment, not to mention taxpayer money in water clean up.

4. Engineered Soil

Builders originally used massive amounts of soil to ensure plants would take root and grow, but the weight was far too much for any home roof, and even most office buildings. Today however, companies have engineered soils to be rich in climate-specific nutrients so less is needed for the same results, regardless of where roofs are in the country, helping make green roofs accessible to all.

5. Building Integrated Photovoltaic Technology

Big, bulky solar panels can be an eyesore that many homeowners would rather not have cluttering their roofs. Luckily, thin film solar technology is becoming a popular option for solar energy, with various companies incorporating solar cells into metal and shingle roofing products. It's a less obvious but still effective method for harnessing solar power. While BIPV is expensive now, Velasquez says popularity will soon make the technology available for homes and office buildings. In fact, building integrated photovoltaics are being used on the China Pavilion (photo) for the China World Expo. The solar panels covering two platforms generate 302 kilowatt hours.

6. Transparent Solar Cells

Solar shingles still seem like too much work for your home? Companies have begun making solar silicon cells so thin they're actually transparent. These cells can be worked into windows to generate energy while still letting light into your home. Christensen says the cells are currently being used primarily in atria windows, meaning the whole ceiling of your office building could be generating power while you work!

7. Light Pipes

Even skylights are getting more high tech -- light pipes are a new technology used to harvest natural light. The fixtures funnel sunlight from large, plastic bubbles on the roof, and channel it through highly reflective, broad pipes into buildings. Orion Energy Systems, which sells the Apollo Light Pipe, says the reflected natural light they produce provides enough illumination on most days to turn off other artificial lighting. However, if it's shady, the Apollo model incorporates fluorescent light bulbs, which use a sensor to keep light shining in even during cloud cover.

8. Personal Wind Turbines

Love the idea of wind energy? Companies are starting to make rooftop turbines small enough for office buildings or even home use. While there is controversy about the availability of strong enough winds in certain areas, companies such as Aerotecture have been working to build innovative wind structures (Aeroturbines) for urban roofs to harness as much energy as possible while being quiet and unobtrusive. Imagine a windy afternoon providing the energy in your house.

9. Cool Roofs

According to the Cool Roof Rating Council (CRRC), cool roofs are the fastest-growing sector of the roofing industry. Some of the most popular new cool roofing used by Tremco involves a combination of white gravel and white glue on flat roofs to keep down cooling costs. The surface is highly reflective, keeping sunrays off instead of absorbing them, which keeps heat out. But the white roof is not being embraced by folks living in colder climates as the color reflects warm sun. To solve that issue, researchers at the Massachusetts Instititue of Technology have recently developed a roof tile called Thermeleon (photo) that turns white in warm temps to reflect heat and then turns black in colder temperatures to absorb heat.

10. Metal Roofs

Christensen's organization gives credit to the new popularity of metal roofs. While metal roofs are not a new technology, their benefits for sustainability are just now being marketed and their availability for an average homeowner has skyrocketed. The metal shingles are extremely easy to recycle, incredibly durable and are a preferred roofing material for homes utilizing rain-catching systems. Also, with the controversy surrounding the use of asphalt in traditional tiles, metal roofs are a truly sustainable way to build.