Sustainability and Passivent natural ventilation

As a sustainable option, Passivent developed passive stack solution for the three-storey building where the passive stack uses natural air movement and convection.

The need to take a 16th Century Grammar School into the 21st century has employed state-of-art techniques that have defied sceptics, achieving a passive energy strategy whilst providing a comfortable learning environment.

Berkhamsted Collegiate School has created new dining and Art and Design facilities, to meet its changing education requirements, and fashioned by architects Short and Associates whose design was selected for its site response and environmental strategy.

Central to the new building and its sustainability is its utilisation of Passivent natural ventilation, which has had a visible impact on the styling, and has been proven by both thermal modelling at the design stage, and in practice now the building is in use.

Robert Grant, Berkhamsted Collegiate School Estate Manager, commented, "I come from an office environment where everything is air conditioned and controlled, so I was very sceptical about how effectively the Passivent system would function, but we are all very pleased".

"The ventilation is working very well".

Passivent developed a passive stack solution for the three-storey building.

Passive stack uses natural air movement and convection, whereby warm air rises.

The warm air is vented through stacks (or chimneys) at high level, creating suction at low level to draw replacement fresh air in.

Surrounding architecture gave Short and Associates the inspiration to include Gothic style turrets, which Passivent has used to form the passive stacks, ensuring even wind pressure to maintain effective ventilation despite the proximity and height of adjacent buildings.

Below, 32 Passivent wall Aircool inlets and eight window Aircools ensure a flow of fresh air into the art history, photography, sculpture, four art rooms, meeting rooms and dining room across the three floors of the building, with each classroom including a dedicated Aircool to create a stack inlet, forming a conduit for the used, warm air and encouraging the flow of fresh, replacement air through the facade and window units.

Thermal modelling by De Montfort University showed the configuration would create up to 10 air changes/hour but would maintain airflow at less than 0.3m/s, maintaining comfortable ambient temperatures and air quality whilst minimising risk of draughts.

It further showed that for only five hours of normal occupancy would the temperature exceed 28degC: Building Bulletin 87 set a limit of 80 hours! A further building design constraint was the site's proximity to both the local railway line and Berkhamstead high street- which meant any windows had to remain closed to comply with acoustic regulations.

The Passivent Aircool units feature acoustic baffles, to minimise external noise penetration and each teaching area is separately vented to minimise risk of noise transfer from room to room.

Passivent is part of the Building Product Design Group and is the UK's leading designer and supplier of natural ventilation systems for both domestic and commercial applications.

The company is a founder member of the NatVent EC-EU-funded project co-ordinated by the Building Research establishment to develop practical natural ventilation solutions for the commercial sector, and has also contributed to the BISRIA Guide BG2/2005 Wind Driven Natural Ventilation Systems, as well as being a member of the DfES steering committee on natural ventilation guidance for schools, Building Bulletin 101.

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