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Good ventilation for today's airtight schools

Mark Quigley discusses the importance of good ventilation in educational buildings
One Of the key factors emerging out of trends in contemporary school design has been the creation of a balanced classroom environment, with optimum Indoor Air Quality (IAQ) at its heart. IAQ has grown in prominence with the onset of better-insulated buildings, raising the matter of 'good ventilation' to the top of the agenda.

A move towards zero-leakage, airtight property is now standard across the building industry as the Government strives to achieve its carbon reduction commitments.

However, whilst carbon savings are key to how buildings are designed, there are a host of vital factors in the build process, and one that is becoming more universally acknowledged is pupil health - achieved through better ventilation.

Poor ventilation is a serious issue. Excessive condensation can cause mould growth, leading to cosmetic and structural damage to the fabric of a building and can create extremely poor IAQ, which can lead to potential health issues for the building's occupants. The level of carbon dioxide in classrooms will also impact pupil concentration.

A correctly designed, specified and installed system will ensure the required performance levels, help reduce carbon emissions and comply with industry regulations. CO2 should never exceed 5,000 ppm, and on average levels should not be in excess of 1,500 ppm. At any occupied time, occupants should be able to lower the concentration of CO2 to 1,000 ppm. When ventilation is supplied at 8 l/s per person, the CO2 concentration will generally stay below 1,000 ppm.

Traditionally, schools have been designed for natural ventilation and good natural light, which resulted in narrow-plan schools with large window space and cross ventilation combined with stack ventilation.

Modern schools will generally be much more air tight, so it's critical that users have control of the ventilation, understand the best system for them and understand how to use it properly.

As trends change, technology evolves to offer a solution, and Xpelair Ventilation Solutions has developed a new technology to meet the demands of school applications.

The hybrid, or mixed mode, low-energy ventilation system is designed specially to enjoy all the benefits of natural ventilation but without the pitfalls.

Unlike its natural or mechanical counterparts, mixed-mode ventilation is, in many instances, the more environmentally and financially sound solution. The underlying principle of a hybrid system is that the school is designed as a naturally ventilated building - without ductwork for air transport, whilst provision is made to assist the airflow through the space when natural driving forces are inadequate.

The Building Regulations Part F and Building Bulletin 101 govern that 'Natural ventilation should be used for standard teaching and learning areas' BB101 2.2. While natural ventilation is an innovative, and sometimes preferable, system it cannot cope with warmer weather, so the assistance of comfort cooling through mixed mode ventilation is an ideal top up solution to maintain a comfortable school environment.

Xpelair's Classmate solution controls the learning environment by automatically reacting to CO2 levels, room occupancies and seasonal and daytime temperatures to maintain optimum IAQ. Since its launch in 2008, and its pilot installation at Williamstown Primary School, Rhondda Cynon Taff, South Wales, the technology has continued to prove its effectiveness in a host of local authority and private school applications.

As part of the £9.5 million development, Williamstown sought to secure an A-rating for environmental standards and Classmate was specified to enhance the learning environment.

The control system selected was designed to provide each classroom, nursery and music room with the correct environmental conditions, acoustic and air quality. The installation was also required to interact with central BMS systems, and in this case, modulating dampers were combined with the operation of high level windows located in the schools central atrium to allow exhaust air from each classroom to exit the building.

Classmate may be the solution to many of the pitfalls to modern zero-leakage building design, but the application has also proved its worth in a host of other applications, too.

Xpelair was specified in early 2011 to provide a bespoke, state-of-the-art ventilation system as part of a £9 million project to transform the prestigious Tonbridge Girls Grammar School in Kent. The school - a nationally acclaimed centre of educational excellence - was in the process of developing a brand new facility with 39 classrooms, a sports hall and a Learning Guidance and Information Centre. Other key considerations to the installation were the orientation and layout of the building, solar exposure, occupancy periods of each room and acoustic performance to eliminate indoor (crosstalk) and outdoor noise intrusion. Xpelair's installation of automatic control panels now allows users to select appropriate ventilation options for each individual classroom.

As a result, lower carbon emissions are looking likely and the school could enjoy energy cost savings of as much as 40 per cent compared with what would have been gained with conventional system installation. Up to six units are now managed from one controller incorporating: timed function, CO2 control, night cooling function, temperature differential sensing and manual override.

In addition to works on the new facility, the school's original 1905 building was also regenerated to cater for music and art curriculum needs, dining and kitchen facilities and lecture theatres - Classmate was specified in both applications.

// The author is the commercial director at Xpelair Ventilation Solutions //
1 April 2014


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