Passivent ventilation for landmark building

Natural ventilation and air conditioning technology from Passivent helps new GBP18m landmark community building achieve 'excellent' NEAT rating.

Passivent's advanced 'mixed mode' strategy unites natural ventilation and air conditioning in one interfaced system, and has enabled Rydon Construction, working with the designers of the Stonebridge Hillside Hub, Edward Cullinan Architects, to meet the client Hillside Housing Trust's desire to provide a building for Brent Primary Care Trust that optimises 'green' solutions and prevents overheating in the development.

As a result of inclusion of the Passivent ventilation and other environmentally-friendly concepts, the health centre has achieved a rating of 'excellent' under NEAT (the NHS Environmental Assessment Tool).

Some 60 Passivent Aircool insulated ventilation louvres have been installed along two elevations on three floors of the Hub's health centre located in one wing of the two-wing, four storey building, which also incorporates community facilities, a convenience store, cafe and 59 residential units.

Each room in which the Aircools are installed also incorporates a Mitsubishi air conditioning cassette, which works in conjunction with the Aircools to maintain the correct level of ventilation, and air quality, throughout the health centre.

To further enhance the environment for patients and staff alike, the Aircools on the lower ground floor have been acoustically attenuated to ensure personal/ private conversations are not overheard outside the consulting rooms or on the street below.

The mixed mode system works by maximising use of the earth's natural air movement principles, and compliments it only when required with the air conditioning to maintain a comfortable, fresh internal environment.

Warmer internal air naturally rises, creating a flow of cooler air into the space through the Aircools.

By drawing outside air into the building, the building is cooled 24/7, keeping internal temperatures comfortable when occupied, and removing unwanted heat when the building is empty.

An Intelligent Controller constantly monitors internal temperatures, and air quality; when they vary outside preset levels, in exceptionally hot or cold weather, the controller triggers operation of the Mitsubishi air conditioning unit, purely to restore the preset internal temperature and CO2 levels.

The system has been proven in 'real life' to achieve a Class A energy rating, with the added benefits of saving almost half the energy used by traditional mechanical ventilation, reduced plant capital and maintenance costs, improved indoor air quality and occupant performance, and greater useable floor space.

David Cawston, in charge of the project for Edward Cullinan, observed, "The contractor's project manager was aware that overheating was often a problem in PCT buildings".

"He wanted to avoid that, whilst optimising control for the occupants and taking into account using 'green' solutions as far as possible, hence his decision, in Edward Cullinan Architects and MLM MandE engineers, to use Passivent's mixed mode system".

"The ventilation, plus other elements such as an insulated envelop with a U value 20% better than Building Regulations, rainwater recycling, and solar collectors, all contribute towards the whole development's energy efficient credentials".

Passivent 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 is a committee member of CIBSE's natural ventilation group and has participated in relevant natural ventilation guidance documentation.

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