Having already produced a class-leading Passive Ventilation system the question was asked: \u201cCan a specialised unit be produced to provide high performance heat-recovery ventilation for classrooms?” The challenge was to produce a unit to fit within the typical restraints of a \u2018tight\u2019 false-ceiling while supplying and exhausting a minimum of 260l\/s at an acceptable sound level to satisfy BB93 and with a target SFP of \u2264 0.9W\/l\/s. This is 45% less energy use than the current maximum SFP allowable of 1.6W\/l\/s (Government directive 2013) and therefore helps with achieving building compliance.<\/p>\n
A further objective was to enable the unit to be turned-down by, at least, 50% air volume without the risk of the heat exchanger going into a laminar-flow condition where no heat-transfer would take place.<\/p>\n