Heat recovery unit
The central recovery unit
Central ventilation recovery unit for the entire building must be chosen such that allows air flow regulation. The need for air exchange rate during the day and during each day of the week is different. The object is to be ventilated and at a time when there is one, although considerably less. At a time when it is necessary to ventilate an empty house just replace the air in the building, about once every 6 hours for normal use of the building is recommended air exchange every two hours in intensive ventilation air must be replaced in less than one hour. Therefore, the ventilation unit should have a maximum hourly capacity at least equal to the volume ventilated (residential) part of the building.
Local recovery unit
The use of local recovery units often occurs after replacing old leaky windows with windows tight. The advantage of local heat recovery units is clearly in the simplicity of installation, since eliminated all HVAC systems, since these are usually units placed directly in the perimeter wall of the building. It is however also quite limiting factor, because in this area are both fans also recuperation exchanger itself. Local recovery efficiency heat recovery units is for this reason, slightly lower than the central unit and it is necessary to take into account the way that is done in a particular unit condensate.