A ventilation apparatus for ventilating a building. The ventilation apparatuscomprises a casing comprising: a cavity for housing a removable heat-exchangecartridge a service door providing access to the cavity a primary andsecondarypathways fluidly connecting the inside of the building to the outside of thebuilding,wherein the primary pathway and the secondary pathway cross the cavity alongabout perpendicular axes a primary ventilator for forcing an airflow in thebuildingthrough the primary pathway and a controllable secondary ventilator forforcing acontrollable airflow through the secondary pathway. The ventilation apparatus,whenthe casing houses the heat-exchange cartridge, has the primary ventilatorforcing aninflow of air through the primary pathway, and (ii) the controllable secondventilatorfor controllably forcing either an outflow or an inflow of air through thesecondarypathway. The ventilation apparatus, without heat-exchange cartridge, has onlyinflow(s) forced through the pathway(s).
