National Library project

The green inverted roof design holds many advantages compared with the non-insulated roof for National Library project

Extensive or intensive green roofs with water features, paths, and plazas can be created on any functional inverted roof construction. The substructure is to be checked for static load-bearing capacity. A vapour-permeable layer must be installed on top of the thermal insulation layer of Synergy isoboards. The green inverted roof design holds many advantages compared with the non-insulated roof:

The thermal insulation protects the root-resistant waterproofing from thermal stresses. During the construction phase, the insulation package provides reliable protection against mechanical strains.
Once the green roof is in use, the insulation layer protects the underlying waterproofing against rakes or other garden appliances used for maintenance. During the construction period of inverted green roofs, there is a clear separation between the trades. The roofer takes care of waterproofing and thermal insulation while the roof gardener is responsible for the substrate layer and greening. This simplifies the final acceptance and warranty. Companies frequently offer green roofs as a complete system. In the case of inverted roofs, insulation materials made of extruded foam boards may not be permanently flooded with rainwater. To satisfy the structural-physical principle of inverted roofs, a vapour-permeable layer has to be applied between the water storage level and the Synergy boards. This may consist of Synergy compact boards. The egg-carton design collects the rainwater on the upper surface and drains off excess water along the cavities on the underside. 
Another alternative is the green, walk-able roof terrace. Part of this design is a non-woven positioned between the Synergy thermal insulation layer and the drainage layer. This layer drains the excess rainwater and offers vapor-permeable coverage for the extruded foam boards on top. Above the gravel drainage layer, the structure can consist of virtually any variation of materials. Part of the roof may be covered with a pond system using welded membranes. Other parts may be converted into a terrace with bedding sand and filter fleece, or filter fleece and a plant substrate to create a green roof on national Iranian library.