Green Roof and Reuse of Collected Stormwater in Buildings in Melbourne - Case Study Example

GREEN ROOF AND REUSE OF COLLECTED STORMWATER IN BUILDINGS IN MELBOURNE CBD Name: Course: Instructor: Institution: City: Date Table of Contents Table of Contents 2 Introduction 3 Green Roof 3 Plant Selection for Stormwater Management 4 Purpose of the Green Roof 5 Water Management System 5 Design of Green Roof 6 Drainage and Irrigation System 7 Maintenance of the Design System 7 Cost of the Design 8 Construction of Green Roof 8 Roof Deck 9 Root Barrier 10 Protection Mat 10 Drainage Layer 11 Filter Sheet 11 Growing Substrate 12 Vegetation Layer 12 Reuse of Stormwater 14 Source 14 Use 14 Kitchen 14 Cleaning 14 Irrigation of roof garden 14 Cleaning 14 Possible Application of the System to a Building Melbourne CBD 14 References 15 Introduction Water reuse and conservation is becoming more important in Australia due to changes in climate, reduction in ground water, drought and reduction in surface water level. In Australia, there are various methods of tapping, conserving and reusing stormwater water. The best system applied in management of water depends on its use. The principle of water management system can help in determining the alternative water sources that can be made available for uses in commercial buildings (Dunnet, &, Kingsbury, 2008). According to Dunnet, &, Kingsbury, (2008), water management system also helps in identifying the appliances considered water efficient. According to Victoria (2014), in Melbourne, various water conservation measures have been integrated to maximize conservation of water for instance, rainwater tapping, efficient water fixture installation, wastewater reuse and efficient reuse of green roof water. Green Roof Green roofs in commercial buildings in helps in management of water and wastewater. A green roof also improves the energy performance in various buildings that has connected them (Victoria, 2014). Green roofs are of two types, which include intensive and extensive. An intensive green roof have a thick soil layer, consists of various plants and habitat, able to retain more storm water, greater energy efficiency and its membrane life is much greater (Victoria, 2014). On the other hand, extensive green roof has a thin soil layer, less plants and is cheaper to put in place. Apart from conservation of storm water, green roofs help in reducing the urban heat effect due to concrete roofs. The reduction of heat helps in energy savings (Victoria, 2014). According to Victoria (2014), in commercial buildings, green roofs are designed to retain stormwater or to evapotranspirate the wastes generated from the plants involved in treatment of wastewater. In order to maximize evapotranspiration, roof plants should be chosen well. The principles that govern the design, construction, maintenance and operation of green roof include, Viability, that is commercially and economically Natural environment protection Minimum greenhouse gas emissions and energy use Maximization of retention and recycling of stormwater Application of healthy work practices and environmentally procedures during construction Cost effectiveness Plant Selection for Stormwater Management Green roofs has challenging conditions for the growth of various plants due to varying temperatures, high light, wind exposure and other hostile sites. Plant selection depends on the selection of the site, maintenance factors and substrate and microclimate (Victoria, 2014). These factors when considered ensure management, functional and aesthetic ensures desirable outcome of the project. The most effective plants for green roof in Australia are the shrubby species and the herbaceous species. These species enhances cooling of the surrounding environment (Victoria, 2014). Purpose of the Green Roof Green roof project is important in water conservation and management of stormwater. The table below provides illustrates various goals of green roof. Green roof design goals Factors to consider Reduction in stormwater run-off Plants with high water uptake Integration and cooling with phovoltaic panels Plant around solar panels, provide irrigation and ensure there are leafy plants Amenity and recreation use Accessibility of roof, increase load of weight Long life Choose light weight components and subtrates, and high stress tolerant plants for example, succulent plants Thermal insulation maximization Selection of leafy plants, provide irrigation, increase substrate depth Water Management System Viability, natural environment impact, minimum greenhouse gas emission and energy use, maximization and retention of stormwater and application of healthy work practices and healthy environment procedures are very important principles when choosing an effective and appropriate water management system (Dunnet, &, Kingsbury, 2008). Commercial building demand for water is on the rise and hence the need for a more sustainable water management measures. According to Victoria (2014), in Melbourne, various water conservation measures have been integrated to maximize conservation of water for instance, rainwater tapping, efficient water fixture installation, wastewater reuse and efficient reuse of green roof water. The rainwater collected from the rooftop is subjected to UV disinfection and filtration which is then stored in underground tank. The water is then closely monitored and could be subjected to chemical treatment if it is necessary in order to maintain its quality (Victoria, 2014). There exists an automatic switch system that switches when water level is low and which ensures automatic connection when the power fails. This switch also ensures manual operation of the system. To ensure elimination of unnecessary wastes there exist an outlet connection towards the downstream (Victoria, 2014). Design of Green Roof Design of the green roof must take into consideration the cost, maintenance, drainage, irrigation and viability of the whole system. The design must be evaluated in order to determine if it is environment friendly and if the process of maintenance is cost effective (Victoria, 2014). Drainage and Irrigation System Green roof must have a good drainage system. Good drainage system ensures the structure integrity is not compromised and to ensure waterlogged substrate does not kill the plants. The drainage must eliminate the subsurface and surface water from the roof in order to help improve the life span of the plants. The drainage system must be able to handle high intense rainfall in Melbourne CBD. A suitable design system must entail all the principles of water sensitive urban design. Incorporation of these principles will help in managing the stormwater in landscape instead of all being drained to waterways (Victoria, 2014). Maintenance of the Design System Maintenance is an important aspect in green roof design. Green roof must be maintained to increase its life span (Victoria, 2014). A particular structure must be assigned those responsible for its maintenance. The technology for the construction of the green roof must be in line with the skills of those responsible for its maintenance. Maintenance of green roof entails checking leaks, periodic inspection, clearing of drains, weeding and repair of loose fixings (Victoria, 2014). Some of the costs involved in the maintenance of green roof include Cost of replacing growing substrate Costs of replacing plants Cost of fertilizer Disease and pest control costs Weeding cost Cost of the Design The cost of the design of green roof depends on the construction materials and the site. Other factors that affect the design of the green roof include Access of the site and its location Transportation cost of materials Material storage in and off the site Access to good lifts and cranes Complexity of the roof design and roof construction and roof penetration Project timing The budget of the green roof project should also consider the future unexpected problems. Construction of Green Roof Green roof consists of series of layer with each layer having specific function (Victoria, 2014). According to Victoria (2014), the main layers of green roof include: The roof structure Waterproofing layer Protection layer Drainage layer Filter sheet Growing substrate Vegetation Other elements incorporated in green roof system include: Irrigation Hard landscaping elements Thermal insulation Leak detection systems Source: Victoria, 2014 Roof Deck Green roof can be stalled on roofs made of timber, concrete and sheet metal. Concrete roof decks are preferred since they are durable, easy to design and enhance structural integrity. Water Proofing Construction of a good green roof requires a watertight roof. Most roofs are waterproof, however some roofs in Melbourne require membrane or some form of treatment to ensure they are waterproof. Waterproof membranes when used must be protected from chemical and physical damage. These membranes can also be coated to increase their life span (Victoria, 2014). Root Barrier Root barriers help in protecting the waterproofing from the shrubs, trees, rhizomes, stolon and woody trees. Root barriers are usually laid over the membrane, for instance polyethylene sheets. They are usually used when the waterproof membrane are not root resistant. Plants produce humic acids when they decompose therefore root barrier must be resistant to this acid. To enhance protection between the root barrier and waterproofing, separation sheets for example HDPE sheets are sometimes installed. These separation sheets also help in separating incompatible materials (Victoria, 2014). Protection Mat Protection mat is directly installed on the waterproofing layer. Mat acts a separation sheet and protects the system from root penetration. Some of the materials used for matting include polypropylene and polyester, which are dense synthetic fibres, hardwearing and water-permeable. Matting also enhances noise absorption capability and enhances water retention on the roof (Victoria, 2014). Drainage Layer Green roof must have a good drainage system. Good drainage system ensures the structure integrity is not compromised and to ensure waterlogged substrate does not kill the plants. The drainage must eliminate the subsurface and surface water from the roof in order to help improve the life span of the plants. The drainage system must be able to handle high intense rainfall in Melbourne CBD (Victoria, 2014). A suitable design system must entail all the principles of water sensitive urban design. Incorporation of these principles will help in managing the stormwater in landscape instead of all being drained to waterways. Some of the drainage materials preferred in green roof system include boards, plastic drainage sheets and permeable layer of rock aggregate. To enhance plant growth the aggregate layer should be low in soluble salts and have a desirable pH (Victoria, 2014). Drainage layer is constructed over the green roof surface. The amount of water that can be stored depends on the cells of drainage layer and the density. Filter Sheet Filter sheet helps in retaining the growing substrate. This layer is able to retain the growing substrate since it prevents clogging of holes and prevents wash-through of substrate particles in the drainage layer. Some of the factors that affect the selection of filter sheet are, vegetation type, substrate type and flow of water through the system. The roots should be able to allow penetration of the roots. Filter sheet should be installed immediately after purchase since it is not weather proof so should not subjected to direct sunlight (Victoria, 2014). Growing Substrate The growing substrate ensures gas exchange at the roots, supports the roots and supplies nutrients and water to the plant roots. Growing substrate consists of a mixture of organic and inorganic materials (Victoria, 2014). The proportion of organic materials should be low since it is usually water repellant hence not easy to re-wet. In addition, its life span is short. A substrate should be stable over time, drain freely and should be of a known saturated weighting (Victoria, 2014). Vegetation Layer Different planting stock can be used in construction of green layer, for instance, seedlings, cuttings, containerized plants and seeds. It is advisable to plant during winter or autumn to enable plants to develop before summer (Victoria, 2014). Image of Green Roof Reuse of Stormwater Source Use Disinfected and treated rainwater Kitchen Drinking Showers Treated and disinfected grey water Cleaning Cooling tower Disinfected and treated black water Irrigation of roof garden Disinfected and treated cooling tower blowdown Cleaning Flashing of toilets Possible Application of the System to a Building Melbourne CBD Reflecting on the research it is important to apply green roof system to help in conservation and reuse of stormwater. The taskforce responsible for the design of green roof must ensure it is simple since green roof has its own challenges including the unusual site nature. Establishment of a successful green roof requires maintenance of the plants and its components. Monitoring should be done regularly to increase the life span of the green roof. References Growing green guide, http://www.growinggreenguide.org, retrieved March 21, 2017 Dunnet, N., & Kingsbury, N. (2008). Planting green roofs and living walls. Portland, Or, Timber Press Victoria. (2014). Growing green guide: A guide to green roofs, walls and facades in Melbourne and Victoria, Australia. Read More