Varmegjenvinner

Varmegjenvinner, or heat recovery unit, is a device used in building ventilation systems to transfer heat from the outgoing indoor air to the incoming outdoor air. The primary purpose is to reduce energy losses associated with ventilation and to improve indoor comfort by moderating indoor temperature and humidity.

Common forms include plate heat exchangers, rotary (enthalpy) wheels, and heat pipe recuperators. Plate heat exchangers use a series of sealed plates to create a counterflow heat transfer path between the two airstreams, typically with low pressure drop and good reliability. Rotary wheels consist of a porous or metal wheel that rotates between the two streams, enabling heat transfer and, in enthalpy wheels, moisture transfer as well. Heat pipe recuperators use sealed tubes filled with a working fluid that moves heat by phase change; they are compact and efficient in certain applications.

Functioning: the two air streams pass through a common recovery element but do not mix. Heat (and, in some designs, moisture) is transferred from the exhaust to the supply air, raising the temperature of incoming air without recirculation of indoor air. The system is driven by a controlled ventilation rate, and in cold climates frost protection may be provided.

Benefits include reduced heating demand, improved thermal comfort, better humidity control in enthalpy designs, and reduced carbon emissions from space heating. Applications are widespread in residential, commercial, and institutional buildings, especially in energy-efficient or climate-positive designs.

Maintenance and installation require proper filtration, periodic cleaning of the recovery element, inspection of seals, and correct ducting to minimize pressure drop. Compliance with local building codes and standards for ventilation and energy recovery is typically required.