Improving the Environment and Saving Energy

Natural ventilation genuinely yields a win:win situation. The concept is proven in ‘real life’ to not only minimise energy consumption but to improve the internal environment, enhance the performance of pupils and staff, and reduce capital, operating and maintenance costs.


You would expect me to laud the system, but Passivent’s natural ventilation solutions have been independently endorsed, winning awards both in the UK and internationally: to name a few, Castle Rock High School in Leicestershire won the PROCON Large Scheme of the Year and Sustainable Development of the Year Awards, and Grainville School won the Jersey Design Awards’ Best Large Scale Development category, whilst as a company Passivent attained the prestigious Sustainable Building Product Award at the 2008 100% Detail exhibition, and our new IC5000 controllers are nominated for the 2009 Building Controls Industry Awards. Further, our authority in the field is recognised and acknowledged: Passivent was a founding 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 contributed to the BISRIA guide BG2/2005 Wind Driven Natural Ventilation Systems.

Additionally, independent research has shown time and again that naturally ventilated buildings reduce incidence of ‘sick building’ syndrome, and enhance occupant performance- be it employees in commercial offices, patients’ wellbeing in healthcare environments or students in an educational establishment.

Passivent natural ventilation systems are proven in real life to be one of the strategies to attain up to an A rating under the new Energy Performance Certificate, which buildings must now have. Their performance enables their qualification for credits under the BREEAM verification system (often helping buildings to achieve at least a ‘very good’ rating). They reduce energy consumption over air conditioned buildings by up to 50%, yield 15% savings on capital costs, 75% savings on maintenance costs, and eliminate the need for a separate plant room: in one installation* the Passivent system is being calculated at reducing energy demand by up to 80%!

The efficiency is achieved by harnessing natural air movement and using it to our advantage, to ensure a draught-free flow of fresh air into a building and extraction of the ‘used’ internal air. In essence, warm air rises (convection) drawing in air at low level, whilst the wind forces drive the ventilation through the systems. The physical principles are combined and controlled to ventilate the building, with the only energy consumption being attenuation of the ventilation louvres regulating the flow of air. The concept is similar to that of a chimney, so is not new. What is new is the application of modern technology- typified by our new range of controllers- to monitor and regulate the air flow, to maintain appropriate levels of fresh air against air temperature, humidity and CO2 levels within, and even optimise ‘night cooling’ facilities.

Navigation Primary School was designed as a flagship for Trafford Metropolitan Borough Council’s education build programme, and is a showcase for Passivent ventilation for the education sector.

The Edwardian school was deemed beyond repair; the new two-storey school incorporates six classrooms on each floor plus a main hall and entrance. Passivent natural ventilation, monitoring of carbon dioxide levels, solar panels, rainwater harvesting and a wind turbine to generate electricity all form key elements of the environmentally-friendly solutions included by designer David Whitehead of Ansell & Bailey Architects and M&E consultants SI Sealy & Associates.

To test the design theory, thermal modelling was undertaken by Passivent and showed the combined cross ventilation/ stack natural ventilation achieved the criteria set for ventilation and overheating within the DfES BB101 guidelines. It also demonstrated that the glazing specification could be changed without affecting the amount of natural daylight whilst reducing solar heat gain, to maintain a comfortable internal environment for the children and teachers. The school was designed with high ceilings to encourage the heat generated by pupils and staff to rise and maintain the desired ambient temperature at occupant level.

Each of the two windows in each classroom incorporates a Passivent Aircool ventilator, to provide the cross ventilation and linked to an energy management system which monitors CO2 levels. The Aircools and energy management system are the only elements of the ventilation strategy to use any electricity. As CO2 levels and heat increases in the occupied classrooms, the system operates the Aircools to draw in fresh air. A further six Aircools- three at high level and three at low level- are incorporated into the glazing of the entrance hall.

Each Aircool uses only 1watt of electricity to actuate its louvres and ventilate the space. The warm, used air rises under natural air movement principles, and is drawn by the stack effect up ducting to the 9 Passivent High Capacity Terminals sited on the roof. The HCTs function as, and provide an architectural reflection of, the chimneys on the original Edwardian school building.

In the main hall, three Passivent Airscoop DAD (direct air dispersal) units on the roof draw fresh air into the space below and simultaneously exhaust the ‘used air’. Passivent Airscoops work on wind power alone, using displacement principles to ventilate the space below. Air moving across the roof is ‘scooped’ down chambers in the terminal into the room. The flow of new, cooler air pushes the internal, warmer air up and out through the Airscoop. Separate inlets/outlets within the Airscoop ensure the airflow is always separated regardless of wind direction.

In the infants’ library and the two corridors, Passivent Litevent units provide natural ventilation and natural daylight, reducing the need in each area for supplementary, energy-consuming electric lighting. Each Litevent provides over 0.6m2 daylight area, up to 88% light transmission and just under 0.6m2 ventilation. Warm air rising is channelled into the glazed dome, and outside through ventilation doors on all four sides of the unit.

Navigation Primary School might include all key elements of our natural ventilation solutions, but the systems have each been carefully designed so they can be specified and installed in any combination, and incorporate additional elements such as sound attenuation- often an issue in educational environments! Sidcot School in Somerset, for example, has had acoustically treated Passivent Aircool units installed in its new £4m Arts Centre, to provide ventilation at low level (ground floor), drawing fresh air into the classrooms whilst attenuating noise penetration from the adjacent A38 to optimise student concentration and learning. Bespoke ‘periscope’ wall units to the first floor allow the fresh air to enter the space, where the ‘used’, warm air is extracted via a combination of high level wall Aircool units and two roof-mounted Airstract units, all managed by a Passivent multizone controller. The ventilation ensured compliance with additional relevant requirements of Building Bulletin 93- Acoustic Design for Schools, and the DCSF schools capital design team report ‘Impacts of the School Environment on Children’s Health & Wellbeing’. BB101 also states that “Natural Ventilation should be used for standard teaching and learning areas with limited computer equipment”.

Rob Barnes, director of HBS Architecture which was responsible for designing the new centre, observed, “Natural ventilation was considered an integral part of the overall design to provide a ‘healthy’ learning environment. As the new complex is located alongside the A38, traffic noise was a major consideration at the design stage, hence the dec
ision to include acoustic attenuation. Natural Passivent ventilation is included throughout all teaching spaces.”

In today’s modern education environment where the pressure for ‘green’ solutions grows by the day, natural ventilation is a proven force which can be tailored to the specific requirements of each project, and one that is increasingly the logical specification for LEA’s. The fact that Passivent has attained the ISO14001 quality standard for environmental management reinforces the company’s commitment to minimising our carbon footprint, and making a positive contribution towards all our futures.

Passivent market a range of ventilation and daylighting products for schools and commercial buildings. For more information please visit or call 01732 850770.

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