Do I have to bypass my VAM unit?

A VAM unit performs a very important role in ensuring that fresh air enters an area. It is also part of the integrated ventilation and air movement strategy for a complete building. The heat balance in the building is maintained due to the exchange that takes place within the VAM. If this does not occur, then cooler than expected air could enter the building, putting additional load on other parts of the system and potentially leading to failures in that system. 

When the heat exchange takes place in a VAM, there is the potential for leakage between air streams , which could be around 8%. Taking all these factors into account we would recommend that a VAM unit is kept as per normal operation to maximise the amount of fresh air entering a space. However this decision needs to be considered as part of a complete building risk assessment.