Effective ESD buildings require the involvement of all players. Scott Drake discusses the ESD strategies used in the Manchester Civil Justice Centre, which has just won the Green Major Project of the Year Award at the UK’s Green Construction Awards.
In only a few short years, the task of making more sustainable buildings has shifted from “desirable but too difficult/too expensive” to being an essential requirement at all stages of project design and delivery. This is because “sustainability” can only be achieved through agreement between clients and users, legislative authorities and product manufacturers, as well as architects, engineers and builders.
The Manchester Civil Justice Centre is a case in point. In commissioning the largest court complex built in the United Kingdom for more than a century, the Department for Constitutional Affairs developed a competition brief that demanded a commitment to both civic presence and environmental performance, in turn staying ahead of the European Union Directive for Energy Performance in Buildings. The brief was motivated in part by the knowledge that visitors and users preferred courtrooms with natural ventilation and daylighting – an obvious response, but perhaps one that reflects the quality of existing facilities built prior to the age of mechanical services. The brief stated: “This building, in line with Government policy for all its new premises, must have a minimal impact on the environment in terms of energy consumption, its immediate surroundings and ecological factors. The court service does not want a building that relies to a great extent on mechanical heating and cooling. The design must demonstrate the use of natural and renewable energy sources including natural ventilation, natural lighting and thermal mass. Waste and water management techniques should be used to conserve water supplies and reduce running costs.”
The competition was advertised in accordance with European Union rules for large civic projects, attracting entries from approximately fifty teams, with twelve interviewed and three selected to develop designs for adjudication. Engineers Connell Mott MacDonald, in association with architects Denton Corker Marshall, recognized the opportunity provided by the project to implement natural ventilation on a large scale in a significant institutional building. Instead of trying to conform to the difficult triangular site and arrange the courts on ground, the architects chose to stack the courts, giving a tall, narrow building form with good access to light and air. This led to the architectural concept of layered elements, which easily solves the circulation requirements of separate entries for the public and the judiciary. It enables legibility by expressing the courts as “fingers” to the north and south, as well as providing clear circulation up and into the public concourse. The narrow floor plate ensures good cross-ventilation for the courts, which are then protected by the environmental veil to the east and the services spine and glazed atrium to the west. In engineering terms, the vertical layout takes advantage of the prevailing winds to move air across the building, and enables the atrium to be ventilated using the stack effect.
Initial plans to use the nearby River Irwell as a heat sink changed when structural testing revealed a large underground aquifer. Engineer Stephen Logan, working on both mechanical and structural engineering, recognized the opportunity that this presented and shifted to borehole cooling using 100-metre-deep pipes to reduce energy use.
Although the predominantly east–west orientation is not ideal in terms of solar access, it does enable the building to face the prevailing westerly winds from the Atlantic Ocean. The temperature and strength of these winds are not ideal for openable windows, but once moderated by the heat loads of the building and the pressure drop through filters and ducts, they deliver natural ventilation to the courtrooms within a very desirable range of comfort levels. (Air intake will be as low as 14°C.) On the services spine to each side of the glazed atrium, horizontal openings on each floor admit air which then travels along ducts and feeds up and into each courtroom. Temperature control to the atrium is achieved through subfloor heating and cooling as well as by vents, and double-skin glazing on the west facade is vented to prevent heat gain. Weather stations on the roof and air quality monitors in each room are connected to a building management system, which controls all of the dampers for natural ventilation. If temperatures become too extreme, mixed mode operation is possible through gas heaters and standard air-cooling units, although the latter are connected to the groundwater cooling.
Within the courtrooms, deep reveals and lightshelves located on the veil provide good quality daylighting, while the veil also acts to give privacy for judges moving through otherwise transparent corridors. It also moderates the effects of wind on openable windows to judges’ suites and office areas, and to natural ventilation grilles and openings. The veil also provides a level of security considered necessary in a city still aware of the IRA bomb that destroyed part of the city centre in 1996. According to the architects, “The Veil aims to symbolize the way in which the complexity, intricacy, and responsiveness of the legal system is always secured by a consistent sense of order and overall clarity; the Law is clear, but by no means simple.”
The project was formed as a PPP (public-private-partnership) with developer Allied London Properties. As part of the PPP, the building is designed to be convertible into offices should the DCA no longer require the courts several decades into the future. While the narrow floor plates would make for interesting office spaces, it is the large floor-to-floor height that makes this building truly unique. The need for high ceilings in the courtrooms has led to heights between slabs of 4.4 metres at lower levels and 5.6 metres at upper levels. This allows space for the natural ventilation plenum – 600 mm at lower levels and 1200 mm at upper levels – to pass above the consulting rooms separating each court from the public areas. The plenum space, described as a light/air duct, is also glazed to allow daylighting to enter from both sides of each courtroom.
Without the white noise from a typical airconditioning system, and with the strict requirement of avoiding sound transmission between courts, acoustic issues were integral to the design of the ventilation system. Problems were avoided by lining the risers that link the plenum to registers just above head height in each courtroom, and by using attenuators designed for mechanical ventilation systems.
The courts are now in operation, and have yet to experience the full heat of summer. According to comfort modelling, courtrooms are anticipated to operate on natural ventilation alone for 63 percent of the year, and energy consumption is likely to be 20 percent less than an equivalent airconditioned office building. Ongoing performance will be important, but what is most interesting at this stage is that the design appears to meet the requirement for civic presence precisely through the expression of its environmental systems, making it apparent that sustainability is no longer optional for such large-scale projects.
Published online: 1 Jan 2008
Words: Scott Drake
Architecture Australia, January 2008