SPECIFYING SUSTAINABLE MATERIALS
The aspiration for any sustainable building is usually using materials with low embodied energy. But, because prison buildings needed be concrete and robust, selecting materials from the Green Guide to Specification was not straightforward. Strict security requirements and MOJ design standards meant that truly sustainable materials couldn’t necessarily be used. Instead, heavy duty materials were chosen by Pick Everard, reducing the need for replacement and repair, and giving the building a longer lifespan.
Achieving the high quality of finish required meant not being able to use concrete with a high proportion of recycled aggregates. The impact of using concrete on such a large scale was carefully considered and most buildings were designed using off site manufacture and prefabricated construction. This provided the MOJ with high quality buildings that were delivered within a demanding construction timetable.
ON NEW
to operate at high system efficiencies, boilers can be monitored remotely via a BMS system, which means changes can be made quickly and efficiently.
The use of CHP was included in the
MOJ’s brief. A gas fired CHP unit runs continuously, providing hot water to all buildings on site. This supports the under floor heating which was cast into the floor slabs of buildings. The system was sized to allow the CHP unit to provide the base heat demand during summer months without extra boiler support.
ACTIVE WASTE MANAGEMENT The MOJ actively pursues better waste management processes for all its sites and in public sector prisons, waste management units are targeted to re-use, recycle or recover a minimum of 35% of all waste generated. Waste is first sorted into recyclable streams by prisoners in the Bioplex unit, using a conveyor belt system, allowing for segregation of recyclables. Separated waste is then deposited into bins, designated for baling and further collection.
back to the main Bioplex unit for processing.
Methane gas produced is used as fuel within the prison development and fertiliser applied to the prison’s farms and gardens, where prisoners learn how to grow food. Although not originally required by the client’s brief, incorporated at a later stage by WSP and Pick Everard, it provides the prison with a long term operational benefit.
DEVELOPMENT
UK-manufactured, prefabricated concrete sandwich panels sourced from specialists in Lincolnshire and Taunton reduced travel miles to site. Using panels with cast-in services, windows and cell doors also eliminated the need for added security protection, which led to higher levels of quality and control, reducing waste and transport of unnecessary materials on to site.
A RESILIENT ENERGY STRATEGY The energy strategy, using different fuels and systems, provided resilience to fluctuations in fuel availability and costs. A central energy centre distributes energy to all the buildings on the site and houses a biomass boiler alongside four dual fuel boilers and a combined heat and power (CHP) unit. The prison site has been future-proofed by having space reserved in the energy centre for an additional dual fuel boiler, should the need arise. A biomass boiler provides heating, fuelled by locally sourced wood chips. Mechanical ventilation in the fuel store removes moisture from the wood, increasing its combustion efficiency. Sized
ANAEROBIC DIGESTION A Bioplex facility uses anaerobic digestion to manage kitchen waste throughout the prison. Anaerobic digestion uses a series of processes in which microorganisms break down biodegradable material, reducing the emission of landfill gas into the atmosphere. The proposed two stage anaerobic digester provides an opportunity for education and training of prisoners towards skilled qualifications, potentially improving their job prospects on release.
Designed to treat approximately 6 tonnes of food waste per week, and capable of digesting up to 1 tonne per day, the system takes waste from the main kitchen, individual building serveries and other organic waste, such as lawn clippings. De-watering systems fitted in all prison kitchens reduce food waste volume by up to 80%. Any liquid waste is discharged into the sewer system and solid waste is fed into the anaerobic digester. Solid kitchen waste is collected from various buildings across the site, and brought
Pick Everard and WSP had previously used this method of waste recycling at HMP Guys Marsh; where a Portagester® anaerobic digestion system was used in conjunction with biomass boilers to create the UK’s first zero carbon prison. At HMP Guys Marsh, fertiliser from the kitchen waste is used along with ash from the biomass boiler on the prison’s farms and gardens.
Based on data obtained from the system at HMP Guys Marsh, the Bioplex facility at HMP Oakwood could result in a 40% reduction in annual landfill waste. Rainwater is collected from roofs of all the buildings and 80% is stored, some of which is used for flushing toilets.
BREEAM ASSESSMENT Twelve different BREEAM assessments were carried out concurrently, using the BREEAM Prisons 2008 criteria and each one achieved BREEAM Excellent. HMP Oakwood is the UK’s largest new build prison and an exemplary scheme illustrating BREEAM Excellent best practice for a prison establishment.
It will be interesting to see how a prison of this scale evolves over time, and how the sustainability principles incorporated through design and construction are applied to the wider custodial estate in the future.
HMP Oakwood is now being run by G4S Care and Justice Services. The first prisoners occupied the prison at the end of April 2012 and the prison is due to become fully operational by October 2012, housing a total of 1,605 category C prisoners, at normal occupancy.
www.pickeverard.co.uk
PUBLIC SECTOR SUSTAINABILITY • VOLUME 2 ISSUE 5 19
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