Creative design and advanced technology incorporated into the development of the Tremco Green Roof System are providing an engineering solution for lighter weight green roofs. These green roofs ensure superior resistance to root and moisture penetration of the waterproofing membrane, unsurpassed resistance to wind shear, and drainage that will enable vegetation to better withstand the extreme climatic conditions of a rooftop.
Tremco Inc of Ohio, USA, offers a system that is designed to optimise the performance of the various complex components as they interact. The system incorporates a waterproofing membrane, root barrier, moisture retention mat, GreenRoof drainage, the growing medium and plants. Components will vary depending on the desired function of the system and the type of load the roof is able to handle.
As with any roof, the ultimate priority is to keep the building watertight. TREMproof 150 built-up hot rubberized asphalt waterproofing membrane or Vulkem 250 GC fluid-applied, elastomeric waterproofing membrane may be used to provide a complete, seamless system to waterproof the roof of the building, eliminates the chance that any water reaching this level will travel to a break in the surface. As a result, leak detection is significantly easier.
The Root Barrier, a 20 mil clear High Density Polyethylene with a double side tape on the outside edge, is installed above the waterproofing membrane overlapping the edges by a minimum of 4” to prevent root penetration. A Moisture Retention Mat, consisting of a double-ply heavy-duty 14-ounce loose woven polyester, is installed on top of the Root Barrier.
The appropriate prefabricated drainage system is placed over the Moisture Retention Mat, maintaining the optimal water content in the growing medium to promote strong vegetation growth and prevent drowning of the roots. One of the primary benefits of a green roof is the decrease in both the rate and volume of stormwater runoff. The soil and plants soak up water, preventing it from immediately running off into storm sewers. Excess water, however, must be removed from the roof area so that the plants will not drown and die from “root rot”.
Fabrics are attached to the top and bottom of plastic core. The top fabric allows water to pass into the drainage core while restricting the movement of soil particles and root growth. The bottom has tall grasses, meadow plants, shrubs and even small trees.
Fabric provides protection to the Waterproofing Membrane. Standard fabric is a non-woven filter fabric that restricts soil particles. A fabric treated with copper hydroxide to stop roots and simultaneously promote the growth of new feeder roots may also be specified.
A variety of natural and manufactured materials may be used as a growing medium. Working with an approved source of growing medium and plant, soil is often mixed with other materials to reduce weight, provide better structure for roots and provide essential nutrients, water and oxygen. The two basic types of green roofs have very different requirements.
The Intensive System, which is designed to be accessible and is often used as a park or building amenity, has large plants with extensive root structures that demand a growing medium of greater than 6” and weights reaching up to 50 pounds per square foot.
The Extensive System, which is primarily built for environmental benefits only, has plants with shallow root growth and demands as little as 2”-1/2” of growing medium.
Green roofs will only function if the vegetation is successful. Succulents and other low growing plants capable of storing water in either fleshy leafs bulbs or roots are most commonly used. For the Extensive Systems, plants selected must be those that can adapt to alpine conditions with little soil, no water, high winds and high sun exposure. Intensive Systems can support a broader variety of
LEED, Leadership in Energy and Environmental Design, awards green roofs one rating point for landscape to reduce heat islands if the green roof is used for at least 50 percent of the roof area and one point for storm-water management that meets LEED criteria.