A green inverted roof, or garden roof, combines the principles of an inverted flat roof with a vegetated roof system. In this configuration, the waterproofing membrane is positioned below the thermal insulation, while the upper layers provide drainage, growing medium and vegetation.
Placing the insulation above the waterproofing membrane helps protect the waterproofing layer within the roof build-up. Above the insulation, the green-roof system is designed to manage water and provide the conditions required for the selected vegetation.
Extruded polystyrene (XPS) is particularly suitable for inverted green roofs because it combines low water absorption and high compressive strength with characteristics suitable for installation above the waterproofing layer.
X-FOAM® HBT can be used as the thermal insulation layer in this type of construction. Its shiplap edges allow adjacent boards to be accurately coupled, helping create a continuous insulation layer beneath the upper green-roof build-up.
Green roofs require careful coordination of thermal insulation, waterproofing, drainage, water management and structural loads, including the weight of the growing medium and vegetation.
