Follow the entire air path
Ventilation supplies outdoor air and removes contaminated air, but performance depends on the route from intake to discharge. Supply to living rooms must connect with extraction from wet rooms and transfer paths between spaces. Closed doors, poorly located terminals or missing transfer openings can change distribution even when the central unit has been sized appropriately.
Heat recovery is not cooling
A heat exchanger reduces part of the heat loss carried by ventilation air. Its rated efficiency does not describe annual system operation: airflow balance, frost control, bypass behaviour and fan electricity all matter. Ventilation cannot replace a summer cooling assessment. The heat it can remove is limited by airflow and the temperature difference, so a ventilation unit should not be assumed to handle every room's cooling demand.
Make room for acoustics and servicing
The shortest duct route may transmit noise to a bedroom or leave no space for attenuation. Provide access for filters, cleaning and condensate drainage, and insulation where duct temperatures require it. Outdoor intakes need coordination with odour sources. Agree routes with beams and suspended ceilings before shaft dimensions become fixed; solving these conflicts on site can compromise both airflow and maintenance access.
Commission the installed network
Measure and adjust flow at terminals after installation, and check noise and controls. A unit datasheet cannot establish that each room receives the intended air. Occupants need operating modes, maintenance instructions based on the equipment documentation and a practical source of replacement filters. Bring room plans and occupancy information to the ventilation discussion. Selecting only a nominal unit capacity leaves distribution, comfort and commissioning unresolved.