Materials for Green Roofs

Green Roofs

Extensive Green Roof

Intensive Green roof

With the increasing urbanisation of the British Isles and the increasing density of housing development we need to do something to reduce its impact. The impact of concentrated air and water pollution, loss of habitat for wildlife and heavy rainfall causing flash flooding as seen in December 2015, can all be lessened by installing more green roofs. Green roofs can also provide localised cooling in summer, aesthetic improvements and help improve people’s well being

With the increasing urbanisation of the British Isles and the increasing density of housing development we need to do something to reduce its impact. The impact of concentrated air and water pollution, loss of habitat for wildlife and heavy rainfall causing flash flooding as seen in December 2015, can all be lessened by installing more green roofs. Green roofs can also provide localised cooling in summer, aesthetic improvements and help improve people’s well being

Green roofs can be loose laid in series of layers before being planted. Extensive green roofs are lightweight with a shallow layer of growing substrate of less than 200mm deep, requiring minimal maintenance. These types of roofs are often planted with low growing succulents such as sedum. Intensive green roofs have deeper growing substrates, support a wider variety of plant types and are designed to carry more weight and people. Such roofs need more irrigation and maintenance and are highly engineered landscapes built on structures with considerable load weight capacity.

Foamit, foam glass subbase can play and important part in green roof build up and this can be supplied Womersley’s Ltd, together with brick dust and lightweight fired clay aggregate for creating growing mediums.

A green roof can help reduce or slow down storm water runoff by the incorporation of water retentive layers and drainage layers with some storage capacity. Retentive layers can include brick dust and organic matter such as bark and storage capacity can be provided by granular aggregate, such as foam glass, within the drainage layer. This is especially important in the winter months when plants have less transpiration. The roof will be designed to drain excess water away but also retain water within the build-up. It is therefore important that a structural engineer checks the dry and wet weight of the roof. Foamit foam glass can act as a lighter weight temporary water reservoir and has a low weight when temporarily saturated.In addition a foam glass subbase and a growing medium above can help insulate the roof of the building in cold weather and prevent overheating in the summer.

The growing medium needs to retain some water within it but not excessive amounts. The table below shows the other factors and requirements for the growing medium.

Source: Green Roof Guide, produced by the State of Victoria, Department of Environment and Primary Industries 2014

Womersley’s Ltd can supply: Foamit Foam Glass Granular, insulating and free draining sub bases; Crushed brick dust with a Saturated Bulk Density of 1090-1300 kg/m3, Dry Bulk Density of 640-720 kg/m3; Foamit 10 with a Saturated Bulk Density of 540-750 kg/m3, Dry Bulk Density of 260-300 kg/m3; Light Weight Fired Clay Aggregate with a Saturated Bulk Density of 540-750 kg/m3, Dry Bulk Density of 260-490 kg/m3;Pulverised Fuel Ash with a Saturated Bulk Density of 1160-1310 kg/m3, Dry Bulk Density of 640-900 kg/m3; advice on the use of materials.