In cold or arctic climates, it is often difficult to get a
traditional mechanical ventilation system to function as
intended during the long winter. The ventilation heat loss
without heat recovery is significant due to the large number of
degree days and draft will also cause problems. If the outdoor
air in cold regions is ventilated directly into the building
through openings or diffusers, the occupants will normally feel
draft because of the very low outside temperature. This is
probably the reason why occupants often block the ventilation
openings resulting in poor indoor climate and higher risk for
moisture problems. Continuous moisture problems will
typically cause damage to the building, e.g. as rot or mould
fungus, which have been documented several times to be
unhealthy for human beings.