Roofs are undoubtedly a necessary part of life, but they can be plagued with problems that affect not just your comfort, but the comfort of everyone around you. Black roofs in particular -- your typical asphalt-shingle roof, for example -- absorb a lot of heat and create an urban heat island effect. The interior of the building can then become a lot hotter than normal, leading to more air conditioning use or more discomfort if the building isn't air conditioned. The problem is compounded if the building is a commercial building because those roofs tend to be flat to accommodate building equipment like compressors. Alternative flat roofs include cool roofs and green roofs, with cool roofs a clear winner if you want to keep renovations low-key.
Green roofs, which have plant life, extra drainage channels, soil, additional waterproofing layers, and more, can add a lot of weight to a building. Sometimes the building can barely handle this amount of weight, and that can create a structural problem that increases the chances of the building being damaged in a quake or storm. Plus, the weight of the green roof can cause the roof to collapse if the work is done improperly.
With a cool roof, especially a particular type of cool roof known as a white roof, little is added to the roof and building other than the white layer and maybe some extra waterproof coatings. This is much easier to handle weight-wise, of course.
Green roofs harness rain runoff and use it to keep the plants on the green roof in good shape. Cool roofs tend not to restrict the flow of rain runoff, but that's not necessarily a bad thing. You can direct the runoff into downspouts that lead to rain barrels, for example, and use it for graywater purposes when cleaning the building. Even in areas like Hawaii, where rain is usually plentiful, it's good to conserve drinking water, and using rainwater for cleaning is one way to do that.
Green roof technology has improved to the point where maintaining the green roof is not a huge chore, but these roofs still require regular care. Plants need to be tended, pathways need to be maintained, and pests need to be eliminated. Cool roofs, though, don't require that work. You have to reapply the cool-roof coating every few years, and there are regular roof maintenance issues as well, but nothing on the scale of a green roof.
Contact roofing companies like Heritage Roofing Hawaii that have done a lot of work in your area to see which buildings they've worked on and which have cool roofs. Representatives from the companies can evaluate your building's roof to see if a cool roof is appropriate.