Soil hauled two”‰ – ”‰or 22”‰ – ”‰floors above street level requires a different composition than the stuff on the ground. It has to absorb a lot of moisture to combat the intensified sun and heat. But once the soil hits its water saturation point, the excess has to flow away easily to avoid building up excess weight. “If things get too heavy, your roof could end up on the first floor,” says Joe DiNorscia, founder of Skyland USA, a Pennsylvania-based company that manufactures “Rooflite,” a specially-formulated lightweight green roof soil.
Rooflite’s seven soil blends are made up of 60 to 80 percent lightweight, ultra-absorbent shale and clay, while the remainder is nutrient-rich organic matter”‰ – compost produced from the straw and hay used to cultivate mushrooms.
Since 2006, Skyland’s Rooflite blends have covered close to 9 million square feet of green roofs. It’s an impressive number, but there’s room for growth: Of the 10 billion square feet of new or retrofitted flat roofs installed annually in North America, only 15 million include a green roof. “We haven’t even begun to hit our peak,” says DiNorscia.