BSEE WATER MANAGEMENT
he need to build municipal areas that can cope with the growing numbers of city dwellers and an ageing population is challenging building design norms, and providing the scope to embrace forward-thinking intelligent design. In order to cater for the surge in city living, mixed-use properties have become increasingly common, with many featuring landscaped gardens, bars, restaurants, water features and residential space under one roof as developers look to exploit every square metre of land.
T
Sean Robinson, specificaon director of water management soluons at Polypipe, discusses how a green roof ecosystem can provide both environmental and sustainability benefits
The use of outdoor areas is considered as a major marketing opportunity for companies in the UK. The garden market including furniture was worth £4.9bn in 2017 – a three per cent increase over 2016 and is forecasted to be nearly £7bn by 2020 (AMA Research).
Furthermore, with the UK climate developing increasingly extreme traits of longer, warmer seasons, interspersed with heavier rainfall, it is essential that our built environment is able to adapt to the changes in the environment.
Far reaching benefits
Built environment innovations such as Blue-Green roof systems could deliver far reaching benefits to UK cities, and offers the chance for building service engineers to expand their skill sets. A Blue-Green roof is relatively simple to install and maintain on a large enough flat roof area, while the spaces created can offer more benefits for end users, by increasing usable green spaces for amenities. This, in turn, increases biodiversity and can assist with climate cooling. With city centre commercial space selling at premium prices, providing a green space for occupants can be a vital selling point for potential buyers.
A Blue-Green roof system also enhances how urban space can be better used in a multi-functional way. For example, the 15-storey, 420,000 sq ft 10 Fenchurch Avenue development in London will boast a striking ‘crown- shaped’ landscaped roof garden, complete with a restaurant, pergola canopies, water feature, a range of climbing and hanging plants, and walking and seating areas. Meanwhile, Manchester City Council’s ‘green and blue strategy’ states that “by 2025, high quality, well maintained green and blue spaces will be an integral part of its neighbourhoods.”
uA BlueGreen roof system also enhances how urban space can be beer used in a mulfunconal way, such as this rooop bar in Bangkok, Thailand
Recycling water, sustaining your building
A Blue-Green roof system is designed to replicate the natural environment and
Adversing: 01622 699116 Editorial: 01622 687031 Water recycling can help building sustainability
improve the built environment. It does this by treating and releasing rainwater at a managed and controlled rate, in line with SuDS best practise or a source control storm water management strategy for attenuation requirements for a development.
Discharge from the storm water drainage system can be managed through infiltration into the surrounding ground, dependent on ground conditions, directly into the storm sewers or adjacent waterways and river systems. Depending on the size of the roof, a Blue- Green system can also negate the need to install deep attenuation systems or basement storage tanks in tall buildings, for example.
A Blue-Green roof system is installed at either roof or podium level above the structural waterproofing membrane and is designed to treat and retain rainwater utilising various proprietary components including outlet chambers, rainwater pipe chambers and separation geotextiles. These components must provide a sufficiently shallow void to accommodate the full storage capacity based on the required controlled flow discharge to suit the project-specific requirements. For example, the Polypipe system Permavoid, is a simple lightweight injection moulded geo-cellular unit that enables a host of design benefits and finishes, while providing a 95 per cent void ratio. On loaded applications, Permavoid can be trafficked during and after installation, protecting the waterproofing layer. On areas where green space is situated, it has a capillary insert in the system which provides passive irrigation to any green areas, roofs, or planters.
For water to reach flow-controlled rainwater outlets on the waterproof surface, these components should provide a multidirectional free-flowing pathway above the membrane. The number of outlets and their position in the installation should be suitable to provide effective drainage for the whole roof surface.
Depending on the design, the aim when utilising the Permavoid system would be to minimise the amount of outlets from the roof or deck, reducing the number of penetrations and work associated with constructing and waterproofing these elements. In practice, it is best not to position outlets more than 100m apart. The number of outlets also depends on the size of the flow restriction within each outlet and amount of water that needs to be attenuated. The discharge rate of the outlets should be designed and manufactured to ensure they can meet the design parameters of the Blue-Green roof system discharge rates. In line with current standards (BSEN 12506-2000 Part 3), emergency overflows should be provided by either:
1. Being incorporated within the flow control outlet.
2. By a secondary method of drainage to facilitate the removal of excess rainfall if the designed capacity is exceeded. The outlet should be installed at the top of the water attenuation layer, or if the design is for greater storage, at the height of the designed storage level.
3. By an overflow pipe/gargoyle discharging through the roof parapet wall.
The lightweight Permavoid system can, in fact, be laid on a flat roof and
16 BUILDING SERVICES & ENVIRONMENTAL ENGINEER DECEMBER 2018 uPolypipe BlueGreen roof used on a commercial building in Aylesford, Kent, UK
uThe use of outdoor areas is considered as a major markeng opportunity for companies in the UK
still drain efficiently. Furthermore, when the system is being used during intense rainfall periods the loading on the roof structure at the storm event capacity would not typically outweigh snow loading requirements.
Filtration components are required within the designed system to prevent silt accumulation or debris affecting the designed volume and flow control outlets.
It is essential to ensure that any thresholds to openings on the roof are adjusted above the designed overflow level or landscaping. Level invert rainwater chambers and access gullies are key to ensuring that the system can be inspected but also cleansed when required.
Maintenance and inspecon
Finally, the operation and maintenance regime of a Blue-Green roof system is not a time consuming task. A planned maintenance and inspection regime is required during the first 12 to 15 months of installation to ensure the planting has taken root, with the major required work being the pruning of the plants. Annual inspections should be carried out on the fixings and water inlets of the geocellular raft to ensure it remains robust and connected to the hydraulic components such as rainwater devices and overflow devices to ensure they are working properly. Inspection is required after period of storms and high winds, to ensure that there is no danger of water leakage from the geocellular raft.
www.polypipe.com VISIT OUR WEBSITE:
www.bsee.co.uk
‘
Depending on the size of the roof, a BlueGreen system can negate the need to install deep aenuaon systems or basement storage tanks.
’
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50
