Passivent stacks up for modular school

Need for additional school accommodation has led Worcestershire County Council to an innovative solution, which is simultaneously believed to be one of the most sustainable modular buildings constructed for educational use.
Restructuring of local schools and growing demand for places at Bewdley High School (the only post 16 education provider in the area) meant the school was facing a pupil roll increase of 360 students this school year. The Council’s solution was to contract off-site construction specialist Yorkon to build a new two-storey block containing 12 classrooms and two science laboratories and a single storey activity studio with toilets and offices, which was as environmentally friendly as possible, including passive ventilation from Passivent, a Biomass boiler using wood fuel and optimum natural light.
To design a ventilation strategy that could be easily installed into the modules and would achieve or surpass DfES ventilation criteria, Yorkon, Ellesmere Engineering and Passivent developed a bespoke scheme using the Passive Stack principle for the classrooms, based around the engineering performance specification provided by Geoff Carter, Worcestershire County Council’s project mechanical engineer.
Each passive 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 providing gentle background ventilation to the BB101 requirement of 5l/s/p. Stack inlet motorised louvres positioned 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 building, and create a constant change of air within the building without draughts. A boost fan was incorporated within the roof terminals to develop a mixed mode strategy and increase the ventilation rate above the specified 10l/s/p when required. The ventilation is controlled via carbon dioxide and temperature sensors, as part of a low energy strategy.
Dermot Galvin, project architect at Worcestershire County Council, observed: “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 number of bespoke elements to create a building that was as environmentally-friendly as possible.”

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