Green building advances don't just focus on things like the building's structure or systems -- there are some lower-tech ways to "green" a building both inside and out. Hanging gardens (like, say, the legendary ones built by Nebuchadnezzar in Babylon) are nothing new, but usually they've been just pretty, not functional (or in the case of me and English ivy, just a sign of lazy landscaping). Here we're talking about a garden system that makes a building more environmentally friendly. When installed on the outside of a building, they can insulate it and reduce heating and cooling costs. Living walls -- also known as biowalls -- also reflect solar radiation, improve air quality by absorbing carbon dioxide and releasing oxygen, and absorb rainwater that would otherwise be runoff. They can also be watered with greywater (water that's been used for bathing, dishwashing or laundry).
Some companies have taken the living wall concept indoors. Obviously, they don't provide the same kinds of benefits indoors, but they can still purify the air and provide a way to recycle greywater. Looking pretty and improving your mood are added bonuses. A plant sitting on your desk can cheer you up -- imagine what looking at an entire wall of lush greenery could do? Both indoor and outdoor living walls are usually modular, made of removable panels with angled pockets to hold the soil. If they're indoors, special lights may need to be installed to meet the plants' requirements. The type of plant depends on where it'll be located and how much maintenance you want to devote to it.