Design Solution · HVAC & Energy
Design Solution · Dream about it
Heat-recovery ventilation paired with night purge to cut cooling demand.
A high-efficiency mechanical ventilation with heat recovery system maintains air quality and thermal comfort while recovering exhaust heat. Night-time purge ventilation flushes the building with cool night air to discharge stored daytime heat, minimising the need for mechanical cooling.
Pairing mechanical ventilation with heat recovery with an overnight purge cycle addresses the tension between airtight, highly insulated buildings and summer overheating: MVHR maintains controlled air quality and recovers heat during occupied hours, while opening the system to night-time free cooling purges the thermal mass that has absorbed heat during the day. The combination is technically sound and increasingly standard in Passivhaus and near-Passivhaus schemes in temperate climates, with good evidence across European housing and education projects. The absence of any measured performance data in this record means the claim that it delivers comfortable outcomes without mechanical cooling rests on the design team's assessment rather than monitored data. The practical risk to flag is that MVHR effectiveness depends heavily on airtightness being achieved and maintained, and the purge ventilation strategy must be driven by a control system — or occupant behaviour — that is actually reliable; a school or residential building where occupants routinely override or ignore controls will see neither the energy saving nor the comfort benefit.
#mvhr #night purge #ventilation #heat recovery