Passive approach inspires Greenpower

The Greenpower Centre, a showcase project to demonstrate the practicality of developing low energy commercial and office buildings has opened its doors. The new headquarters for Greenpower Education Trust has been developed in partnership between architects Emission Zero, Fordingbridge plc and Passivent to provide an inspiring learning environment and innovative test bed for low emission technologies.

The building itself demonstrates the concept, having achieved the best A rating for energy performance.

Using innovative ventilation technology pioneered by Passivent, the building combines two types of passive (natural) ventilation, one for the building’s open office and lecture area and an iMEV system for the toilets. The former is managed by a control system, which also operates the air source heat pumps and enables the occupants to change the settings via the integral web browsing facility.

The ventilation strategy harnesses the passive stack principle, whereby warm air rises, pulling in cooler air behind it. The two-storey high building’s front façade is constructed almost entirely of glass and the Passivent Aircool ventilation louvres, which are set into the façade at low level, combine with Passivent Airstract terminals on the green roof to implement the ventilation.

Cool air

The Aircools supply cooler external air into the building. The Airstracts act like chimneys, drawing the warm, used internal air upwards and outwards, creating planned air paths for the fresher air to circulate through the building’s open office and lecture areas. To further enhance the internal environment, the Airstracts have been acoustically treated to minimise noise penetration from the adjacent busy A27 trunk road.

Both Aircools and Airstracts are linked to Passivent’s advanced iC7000 control system. The controller constantly monitors air quality and temperature, adjusting airflow to maintain the desired ambient warmth and CO2 levels within whilst allowing temporary or permanent over-ride. It can also enable cool air to enter the building in warmer periods, and provide night cooling which is essential because of the solar gain through the high proportion of glazing.

In the toilets, Passivent’s intelligent iMEV system integrates intelligent extracts and an intelligent fan within a central extract system. The extracts open and close in response to varying humidity levels. The central fan is constantly monitoring the extracted air and when it detects that the humidity content is more than a pre-set level, it boosts the extraction rate. As the extract will be open only in a room with a high level of humidity, boosted extraction will only take place in that room. The system works without any occupier input, and ensures the interior remains fresh, dry and odour and condensation-free, even when the building is unoccupied.

Sustainable engineering

Neil Rideout, joint Managing Director for Passivent says: “We have worked with Greenpower for some years, helping to encourage its promotion of sustainable engineering and design.

“The new headquarters aims to inspire and encapsulate Greenpower’s objectives to provide an inspiring learning environment and test bed for low emission technologies; our focus on harnessing natural resources such as air movement and daylight in construction sits logically alongside.”

Natural ventilation is proven to reduce capital costs by 15%, operating costs by 50%, and almost eliminate maintenance costs, over conventional mechanical ventilation. It is also proven to reduce the incidence of sick building syndrome and improve the performance and productivity of the building occupiers.

Aircool ventilators are installed in the building façade to provide controlled fresh air intake or extract as part of a natural ventilation system, or in conjunction with mechanical cooling systems where they can reduce the need for daytime cooling and air conditioning. Using just 2W of electricity to operate the ventilation louvres, the Aircool units can be minutely adjusted to control airflow requirements taking into account the weather outside, the speed and direction of wind, rain, temperature, and the location of the units within the building façade, to ensure a gentle flow of fresh air into the building without draughts. Thermally broken and insulated, the units are more thermally efficient when closed than a standard double glazed window, thanks to a controllable damper.

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