Design Solution · HVAC & Energy
Design Solution · Dream about it
Roof stack units (fan-assisted) ventilate large halls.
Roof-mounted stack ventilation units, assisted by fans when buoyancy alone is insufficient, ventilate dining and main halls that have high, variable occupancy. The stack effect does most of the work, with fans only topping up, keeping energy low.
Roof-mounted stack units use buoyancy-driven airflow as the primary mechanism, with fans supplementing only when thermal driving forces are insufficient for the instantaneous load — a strategy well-matched to dining halls and assembly spaces where occupancy is high and intermittent. The energy logic is sound: fan power is avoided for most of the operational hours and called upon only at peak, which materially reduces annual consumption compared with a fully mechanical system. This record provides no supporting evidence, so performance figures remain uncorroborated, and the design of a hybrid natural-mechanical system requires more careful modelling than either a pure natural or pure mechanical approach — the hand-off between modes, the control logic and the risk of reverse flow through passive openings when fans are running all need to be resolved in simulation before construction. The practical constraint in an existing building is the roof penetration: installing stack ventilators into a live school or similarly occupied building requires either a well-phased programme or significant temporary provision, and structural checks on the roof zone to take the units are necessary early.
#stack ventilation #buoyancy #halls