The energy benefits associated with green roofs will be greatest for one- or two-story buildings, where the roof surface constitutes a large proportion of the building envelop.
Green roofs offer one of the most effective methods for protecting roof membranes from damage during storms, so consider contacting a local roofing contractor to get more information.
Some roofing materials are more waterproof than others. Newly installed roofs are usually very watertight, but that changes as they get older. There are professionals that are experienced in roof waterproofing services for roofs which are a few years old, but not old enough to replace. Special coatings are used to form a membrane on any style of roof which keeps water from leaking in.