The best type of green roof for the hotel's space, given the weight limitation of 20 pounds per square foot, is an extensive green roof.
Extensive green roofs are lighter and typically have a soil depth of 2-6 inches, allowing for a wide variety of hardy plants like sedums and grasses that require minimal maintenance. In contrast, intensive green roofs require deeper soil (usually more than 6 inches) and support a wider range of plants, which can exceed the weight limit the roof can handle.