Natural ventilation: a breath of fresh air for St Mary Magdalen School

Several studies undertaken by organisations such as the Building Research Establishment (BRE) have highlighted the fact that design and air quality can significantly affect the behaviour and attainment levels of pupils in areas such as attendance and SATS results. It is also now recognised by the government, local authorities and schools building designers that ventilation and internal air quality (IAQ) are important elements in providing an appropriate environment for learning.

Sustainability, too, is essential in any new construction project, and using natural rather than mechanical ventilation provides a climate controlled environment that is sustainable both in terms of the amount of energy it saves and in keeping costs down.

By harnessing the natural forces of thermal buoyancy and differences in wind pressure, natural ventilation creates air circulation with minimal use of electricity. Therefore, when consultant Halcrow Yolles was looking for a ventilation solution for St Mary Magdalen’s RC school in Willesden Green, North London, natural ventilation actually offered two solutions. Firstly, a specialised system of natural ventilation was installed to capture moving air outside the building, and another specialised system was used to control windows in the building to circulate the air, maintain interior climate and reduce CO2 levels where required. Halcrow Yolles was also fortunate to find a single source for the two different systems within the VKR Group – Monodraught, the leading supplier of natural ventilation and natural daylight systems and WindowMaster, Europe’s largest provider of natural ventilation and smoke detection solutions. The combined resources of the two sister companies provided the ultimate natural ventilation solution.

Monodraught supplied and installed a total of eleven Windcatcher natural ventilation systems – seven 900mm square models for classrooms and four 1200mm circular models for the hall and a studio. The roof-mounted Windcatchers capture the prevailing wind and direct it to the classrooms and hallways below via a series of dampers. They also remove stale air from the interior; and act as a form of extraction, inducing cross-ventilation in the spaces.

In addition, Monodraught supplied and installed nine 450mm Sunpipe Diamond dome natural daylight systems.

WindowMaster was chosen to supply its NV Advance™ window automation systems for the school because of its ability to provide a complete installation, in particular the central computer control system. The installation includes 153 motors on 115 façade windows, 16 motors controlling 16 roof windows, various temperature sensors and a weather station.

To protect pupils WindowMaster’s NV Advance™ system, which is the only system in Europe that intelligently monitors windows to prevent entrapment, incorporates ‘intelligence’ within each of the motors used to open and close windows. Microprocessors installed within the devices monitor in real-time the amount of electrical current being drawn and the precise position of the window to an accuracy of less than a millimetre. This means that if an object, hands or fingers, become trapped in a window and prevent it from closing, the amount of current drawn by the motor instantly increases. This is detected by the microprocessor, which immediately reverses the motor to release the window, therefore preventing the possibility of serious injury.

The weather station monitors external conditions around the building, including wind direction and speed, temperature and rain fall. Readings taken from the weather station and sensors fitted internally are analysed and compared to specified parameters. Windows around the school are then precisely positioned to keep air quality within rooms fresh and the temperature constant, naturally ventilating the building to prevent overheating and improve air quality for staff and pupils.

During summer months the natural ventilation system supplied by the two VKR Group companies automatically flushes the building with air from outside to cool rooms during the night so they are fresh for pupils in the morning. This also minimises heat gains during the day, allowing a comfortable climate to be maintained, while retaining security at night. During summer nights, the natural ventilation system takes advantage of the buildings structure to reduce the internal temperature during the day. This is achieved by the rooms’ exposed concrete ceilings, which act as a heat sink during the day. When the building is purged with cool night-time air, heat is removed ready to absorb the next day’s gains.

Partnering with Monodraught and WindowMaster enabled the school to take advantage of interactive natural ventilation solutions; and the finished building and its learning spaces now benefit from high levels of natural ventilation and natural daylight as a result.

Windcatcher and Sunpipe are registered trademarks owned by Monodraught Limited.

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