Green roofs usually save money over the long term. For industrial installations with large heating and cooling costs, a green roof can save enough to cover its extra up-front cost in just a few years. For smaller buildings the payback period is longer, but a green roof almost always pays dividends over its full lifespan. It also increases a building's resale value, plus its desirability helps lower vacancy rates.
The benefits of living architecture in buildings dedicated to wellness; hospitals, hospices etc., is becoming well known, The health and well being of patients of students in institution buildings using green spaces extensively is greatly improved and well documented.
Costs vary greatly, but an extensive green roof with 100mm of grow medium is commonly in the range of $13 to $16 per sq. ft., including installation and plants. On a large scale installations using sedum cuttings and 60 mm of grow medium, it can be as low as $9 per sq. ft.
Deeper grow medium, green roofs that employ elaborate landscaping design with combinations plants, full size shrubs bushes and trees. The soil or grow media/substrate layer is usually 300 mm - 1500 mm: 12" + and the entire system has a saturated weight of greater than 45 lbs. per square foot, average being about 50 lbs. per square foot.
Sloped green roofs extremely attractive and highly visible from the ground, however they have unique challenges and need to deal with erosion and shear forces due to gravity. The soil or grow media/substrate layer is usually 100mm - 200mm: 4-6" and the entire system has a saturated weight of less than 35 lbs. per square ft. - average being about 50 lbs.per square foot.