What is Positive Input Ventilation (PIV)

What is Positive Input Ventilation (PIV)

By Ruth MacEachern

Product Manager

Positive Input Ventilation is a system that draws fresh air from outside a building in and then distributes it into all rooms through a centralised system that is usually mounted in the loft before expelling the air outside.

A conventional extractor fan that you might find in a bathroom or kitchen is an effective way of removing humid air from a building to reduce the condensation that causes damp; however, an extractor fan simply removes air.  A Positive Input Ventilation System (PIV) closes the loop of airflow by controlling and filtering the air that is drawn into the building to replace the humid air that is removed by the extractor fan.

A Positive Input Ventilation is a whole house ventilation system that improves air quality in all rooms.  It is highly effective at minimising condensation and, thanks to the filtration of fresh air as it is drawn into the building, PIV will also reduce the concentration of allergens such as pollen which are drawn into the house.

How PIV Works

A positive input ventilation system uses a central unit which is usually mounted in the loft.  This unit includes the fan systems which are connected to the outside and through ducts to rooms around the house.  The advantage of the system being mounted in the loft is that the air drawn into the house is from well above ground level, and as such contains far fewer of the pollutants from vehicles that are concentrated close to the ground.  Additionally, having the system mounted in the roof means that it will be warmed by the natural tendency of warm air to rise through your home and the solar gain from the sun shining on your roof.

The fans mounted in the loft draw air in through filters and then “pump” it through the duct system to outlets that are positioned in the walls or ceilings around your home.

As the air flows through the house, it carries the humidity and dust particles with it to be safely extracted.  This leaves the indoor air clean and pleasant.

Installing a PIV System

A PIV system is professionally installed in a home and does not require building work to be carried out.  As such, it is suitable for fitting in an existing building where improved air quality is required.

The process of installing a PIV system requires the fan system to be placed in your loft and for ducting to be connected to it.  The central unit needs to have an external vent to draw in air – this can be under the eaves or through the roof depending on the system used and the design of your home.

Holes are cut into the plasterboard of ceilings in the rooms where vents are to be installed and the pipework is mounted on the ceiling. 

To meet building regulations and to ensure safety, the PIV system needs to be connected to the mains by a qualified electrician.

Benefits of PIV

A PIV system is a highly effective way of improving indoor air quality.  The constant movement of air through the building prevents the build up of condensation and also reduces the concentration of volatile organic compounds, allergens such as pollen, and even radon gas in your home.

The reduced condensation will remove damp areas while the airflow will also remove cold spots around the house and make your central heating more effective.

PIV systems consume very little energy when running and include sensors that allow them to adjust the amount of airflow depending on the level of humidity in the air. 

If your home suffers from high levels of condensation, or you live in an area which is prone to radon gas, then Positive Input Ventilation systems can help you enjoy your home while also reducing the risk to your health of low-quality air.  Speak to one of our specialists to arrange a survey and find out more about whether Positive Input Ventilation is suitable for your home.