Positive input ventilation (PIV)

Firstly, positive input ventilation (PIV units) is a type of residential air ventilator that aims to renew indoor spaces by forcing out stale air through natural gaps in the building.

To do this, a unit is typically installed in the loft of a home. From here it can collect and filter outdoor air that makes its way in through the roof. Through a ceiling-mounted diffuser, this clean, filtered air is then circulated throughout the structure, gently pushing old air out at the same time.

While this method is simple and cost-effective to install, these systems still rely on natural ventilation to work. As a result, this method is unlikely to generate meaningful savings as valuable heat energy is still allowed to escape.