What Is A PIV Unit / System

what is a piv unit

Often homeowners with ongoing mould problems may hear that a PIV unit would be useful, but what is a PIV unit, how does it work and what will it actually do?

The first thing to know is that PIV stands for Positive Input Ventilation. This means that it is a small ventilation system which operates by trickling fresh, filtered air into the building which pushes the damp, humid air out of the building.

Fresh air in – Humid air out.

How Does a PIV Unit Work?

When a house high levels of condensation present it is often due to poor ventilation leading to a build up of moisture in the air. In turn this condensation moisture will settle out on walls and ceilings causing black mould to grow.

The PIV unit works by continually taking clean and fresh air from the loft space and feeding this slowly into the property. As this happens the air in the house is put under positive pressure causing the stale humid air to flow out through the gaps and vents in the house.

how does piv unit work

Benefits of a PIV Unit

There are many benefits from having a PIV unit installation in your home. Some of main ones are shown below.

  • Stops Condensation

    If you suffer with condensation on windows or walls you will notice an improvement once a PIV unit has been installed.

  • Prevents Mould Growing

    Mould grows on the clean pure water provided by condensation. By taking this away the PIV unit will prevent mould problems in any building.

  • Low Energy

    The PIV units we install typically use just £20 worth of electricity per year!

  • Perfect For Landlords

    The PIV units is usually installed in the loft meaning that tenants have limited access to fiddle with it. The result is tenants live mould free and landlords get far less complaints. Helps meet landlord obligations under the Homes (Fitness For Human Habitation) Act.

  • Quiet Running

    Generally PIV units are inaudible on the lowest settings with most of the equipment being in the loft space.

  • Fresh Air Whatever The Weather

    The unit will continually push fresh filtered air into the building, regardless of the weather outside.

Types of PIV Units

what is a piv unit
An Airtech Loft Mounted PIV Unit

The loft mounted PIV system is the most commonly installed type of unit.

The bulk of what you see in the picture is fitted into the loft space with just a small dinner plate sized white disc visible in the ceiling. Generally this visible part will be in the ceiling at the top of a landing or in the hallway of a bungalow.

The system is usually hung from the roof joists and connected to the mains electricity by a qualified electrician.


The wall mounted PIV unit is perfect for flats and apartment which do not have a suitable loft space.

The system is ducted through the wall to the outside and pulls fresh air in through the installed pipework.

Generally the system would be installed in a central position such as in the hallway.

wall mounted piv unit devon

We Install PIV Units Across The South West

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