Passivent stacks up for modular school ventilation
Contributing to the environmental credentials of new accommodation at Bewdley High School is Passivent natural ventilation.
Faced with an increase in the number of students of 360 at Bewdley High School this year, Worcestershire County Council contracted off-site construction specialist Yorkon to build environmentally friendly accommodation. Restructuring of local schools and growing demand for places at this school, the only provider of post-16 education in the area, led to the increasing number of students. A new 2-storey block contains 12 classrooms and two science laboratories. There is also a single-storey activity studio with toilets and offices. Environmentally friendly measures include Passivent passive ventilation, a biomass boiler using wood fuel and the optimum use of natural light. To design a ventilation strategy that could be easily installed into the modules and achieve or surpass DfES ventilation criteria, Yorkon, Ellesmere Engineering and Passivent developed a bespoke scheme using the Passive Stack principle for the classrooms and based around the engineering performance specification provided by Geoff Carter, the county council’s project mechanical engineer. Each Passivent stack links a ground-floor and first-floor classroom, minimising the number of roof terminals. Fresh air is drawn into each classroom via an Aircool ventilator unit below the window and past the radiator to provide gentle background ventilation to the BB101 requirement of 5 l/s per person. Stack inlet motorised louvres in the suspended ceiling draw the fresh air diagonally across the classroom and up the passive stack riser. High-capacity air-discharge Airstract terminals on the roof draw the used air out of the buildings and create constant air change without draughts. A boost fan in the roof terminals develops a mixed-mode strategy and increases the ventilation rate above the specified 10 l/s per person when required. Ventilation is controlled via carbon-dioxide and temperature sensors as part of a low-energy strategy. Dermot Galvin, project architect at Worcestershire Council, comments, ‘The primary driver for the decision to use off-site construction was time. Yorkon and Passivent showed the flexibility to meet our specific requirements, including a umber of bespoke elements to create a building that was as environmentally friendly as possible.