and the greater the complexity, the more likely things wouldn’t work properly and energy costs would rise. ‘For some reason, we seem to assume
that an automated natural ventilation system will work better than a window, and be commissioned correctly.’ Bunn revealed several examples of
schools that had been designed to allow for natural ventilation, but were not operating successfully because they had never been properly explained to the occupants or shortcuts had undermined the strategy. In one case, all the chains on the
motorised windows had broken because the sub-contractor had changed the motor specification to save money. He also found control panels obscured by shelves or positioned where teachers couldn’t see them. ‘It is easy to find examples of classrooms
with the lights on, blinds down, and the windows open, even with trickle ventilation in place – and there’s nobody in the room,’ he added. Engineers need to provide clearer instructions and think about usability when fitting switches, and so on, he said. ‘We must ask ourselves if it is the
solution the user wanted or what the designers thought the user ought to want,’ said Bunn. ‘We are very good at providing the feature, but not so good at the function.’ To get the controls right, there must
be good integration in the project team, according to Nick Huddleston of SE Controls. ‘The natural ventilation strategy
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will determine the controls hardware so the M&E specification must co-ordinate with the architect’s specification – but they often don’t and this leads to spiralling operating costs.’ Control experts at the conference
stressed the importance of monitoring wind pressure as the key influencer on natural ventilation followed by temperature and building shape. Window openings need to be finely controlled so they can open to appropriate distances, based on over or under pressure created by wind movement around the building. ‘The first 5cm of an opening is the
most important for natural ventilation,’ said Carl Sutterby of WindowMaster. ‘So the controls need to be dynamic and able to adjust settings at regular intervals. However, they must also be easy for the user to understand. If they are too complex, they will not be used and the school staff will revert to manual control, which will undermine the whole natural ventilation strategy.’ So, complexity is to be avoided, but we
do need clever control strategies; beware product-based solutions that lack detailed operating data; and, above all, make sure the teaching staff know what you are trying to achieve and how. It could just work, but the designers, project managers and specialist suppliers will have to be properly integrated and singing from the same song sheet if they are not to end up in detention for failing to deliver again.
January 2012 CIBSE Journal 27
Loxford School in the London Borough of Redbridge, which was New Build Project of the Year runner-up in the CIBSE Building Performance Awards 2011, uses natural ventilation with night- time cooling from exposed concrete soffits (see the Journal, March 2011, page 42)
Aedas/Max Fordham
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