However it was found in the process of extracting the stale air from the space you wish to ventilate the heat generated to maintain the room at a set temperature went with it. Basically a costly exercise of heating air up only to expel it! Conversely in the summer money spent on cooling down the internal spaces was expelled resulted in a similar waste. 

 

A solution to this is to install a Heat Recovery and Ventilation (HRV) system which recovers energy, either hot or cold, from the outgoing extracted air and transfer it to the incoming fresh air by means of a plate heat exchanger. This then tempers the fresh air accordingly without mixing the two air streams. Current equipment around can recover and re-use up to 70% of the outgoing energy therefore reducing the heating or cooling load to the room thus reducing running costs.