The CABI Building
The CABI HQ building is split into two main two-storey buildings, each of which boasts a substantial, sloping green roof that descends from the apex of the building right down to the ground at the base of the building. The beautiful, sloped design of the green roofs allows the building to completely blend in with the natural landscape surrounding it – making it almost invisible.
Background to the project
The Centre for Agriculture and Bioscience International (CABI) is a non-profit organisation which tackles global challenges such as improving global food security and safeguarding the environment. They are well known for the substantial amount of support they provide to farmers in developing countries. Their new HQ, situated in an Area of Outstanding Natural Beauty, was specifically designed to be environmentally friendly and energy efficient.
The Project
Access Irrigation were responsible for the design and supply of the complete irrigation system watering both green roof areas at CABI HQ. The system was fully automated, using a Heron Mi irrigation controller. This controller has a large digital display for easy, accurate programming and a very high level of reliability. To prevent operation in wet weather a rain sensor was included. Solenoid valves were used to split the system into sperate zones, to allow each zone to operate at a separate time, thereby enabling good water flow and therefore efficient watering for each zone. The solenoid valves were connected to the controller via signal cable. Both the controller and solenoid valves were housed in the roof level plant area. The system was designed to be fed from a tap also located in the roof level plant area.
Each solenoid valve is opened and closed in sequence by the controller. When the first valve opens, the pump will detect a drop in pressure (due to pressure release from the open valve) and will begin to operate to boost the pressure back up again. This will cause water to flow through the first (now open) solenoid valve to water the first zone. The controller closes the first valve, and immediately opens the next valve in the sequence. Once the last valve has closed, the water flow will cease, and pressure will build again, and the pump will stop operating.
The irrigation system was split into a total of 12 zones – with 6 zones watering each green roof. A total of 12 supply pipes (6 supply pipes for each green roof) were used to run from each of the 12 solenoid valves to each zone of dripline on the green roofs.
Both green roofs were watered using Permadrip-Pro dripline. Permadrip-Pro is a brown coloured dripline designed for landscape irrigation with a 16mm pipe diameter and a wall thickness of 1.2mm. The 1.6 L/h drip emitters are pressure compensating, ensuring uniform output over a wide pressure range and include a built-in anti-siphon mechanism, to prevent dirt being sucked into the drippers at the end of the irrigation cycle. These features make it ideal for sub-surface use and for use on sloping sites. The emitters also have a large inlet filter and unique, continually self-cleaning design, providing excellent resistance to blockages. Dripline of 0.15m dripper spacing was used, laid out in rows widthways along each green roof. Dripline near the flatter part of the roof at the roof apex was spaced at 1m intervals, whereas dripline on the sloping parts of the roof was spaced at 2m intervals.
The Result
Our project at CABI HQ has resulted in a building that completely blends into its natural surroundings, with the substantial green roofs attracting insects and birds and thus enhancing biodiversity. We are delighted with the result and are proud to play our part in helping a reputable organisation like CABI to thrive whilst simultaneously having a positive impact on the natural environment.
