Natural Air Ventilators used in school building renewal

The Government commitment to renewal of our school buildings, coupled with a greater understanding of comfort conditions required, is leading designers to the use of natural air ventilation systems in order to achieve a balanced internal environment for pupils and teachers.
While openable windows offer primary ventilation, it is often difficult to use them due to draughts, rain, cold and noise issues. Roof mounted air systems often rely on wind and wind direction, therefore while they offer some opportunity for air intake and extraction at high level, many leading designers are introducing low level natural air ventilators (NAVs) at or below window level, the purpose of which is to control ventilation (to ensure an adequate supply) and so prevent build up of carbon dioxide during the day. These natural air ventilators normally comprise of an external louvre for weather protection and an internal electrically controlled damper, linked to the BMS. Another benefit of NAVs is their use in night-time cooling systems as they do provide security against building entry.

The use of NAVs is not restricted to school projects as the same principle is being explored for commercial buildings where a balance between natural air ventilation and mechanical ventilation is sought.

The use of NAVs is still a developing science. As such there are no defined standard sizes as each application tends to be bespoke to suit the needs of the designer in achieving the desired balance of natural air and mechanical ventilation. However there are some guide lines to follow: The NAV external louvre can be a simple ‘standard’ louvre or of a higher performance design, depending on the exposure of the building. NAV damper units can be single skin or insulated panels housed within a thermally broken frame system. Damper blades can vary from single small blades to multi blade units depending on size requirements. Grilles, fixed or adjustable, may be fitted internally to provide a functional and decorative appearance.

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