According to Bradford Insulation (CSR) , mechanical ventilation is typically employed to remove contaminants and reduce internal temperatures in buildings with a high level of human occupation such as warehouses, offices and schools.
Mechanical ventilation is also preferred in buildings that have high levels of airborne contaminants such as factories.
However, traditional building ventilation options are being reviewed given the increasing energy costs and carbon tax regimes to ensure a cost-effective solution that is good for the environment inside and outside the building.
Roof mounted electric powered axial fans are the most limited form of mechanical building ventilation. While offering a guaranteed high extraction rate, the units are either on or off, regardless of the prevailing conditions.
These ventilation systems consume high levels of energy, producing carbon emissions with the result that they are operated only when the building is occupied. When switched off, they do not contribute in any way towards maintaining the building’s desired environment thermal and air quality environment.
Natural ventilation in the form of roof mounted wind driven ventilators is the most environmentally-friendly form of building ventilation. There are no ongoing operational costs in the form of electricity consumption or carbon emissions as they are driven by the warm air in the building rising towards the roof in addition to wind movement across the turbine.
However, wind driven ventilators are dependent on these forces to operate, so in periods of reduced temperature or low wind, the vents’ performance will decrease correspondingly.
Hybrid ventilation is an evolving form of building ventilation that combines natural ventilators with very low energy motors to offer energy-efficient continuous ventilation. The natural ventilators operate during favourable conditions with no operating cost.
When the ventilators are running in powered mode they consume a low amount of electricity and therefore produce less carbon emissions.
Hybrid ventilators not only use less power in powered mode but also need to run only for shorter periods due to the availability of continuous ventilation in natural mode, allowing for similar air change rates over a day compared to mechanical ventilators, which must run for longer periods.
Hybrid ventilation systems also offer the additional benefit of reduction of thermal mass in a building. Since the ventilators are capable of operation in natural mode without using electricity, especially when the building is not in use, continual ventilation is achievable.
Once the external temperature drops below the internal temperature, cold air is brought into the building, cooling the inside atmosphere overnight and facilitating easier control of indoor temperature during the day.
Natural ventilation has been used extensively in the Middle East to ventilate factories, warehouses, transportation depots and military facilities. Trials in the harsh environment of the region have shown reduction in building temperatures by up to 4ºC-5ºC at 34ºC+ using natural ventilation systems.
Edmonds produces a comprehensive range of natural and hybrid ventilation systems for customised applications and has developed proprietary software to aid in the development of ventilation schemes under AS4740.
A world-leader in wind and hybrid powered rotary ventilators, Edmonds is part of Bradford Insulation (CSR).