Positive Input Ventilation

Positive Input Ventilation (PIV) works by drawing in fresh filtered air from outside and distributing it throughout the dwelling. This creates a positive pressure environment, which helps to dilute and reduce the buildup of moisture and pollutants in the air.

PIV systems are particularly effective in reducing condensation and mould issues, which can cause serious health problems, and damage to your property.


Our PIV ONE units have been designed with easy installation and low maintenance in mind. The units are quiet running thanks to an energy-saving EC motor and our Plus+ model also features heating and further control ability.


Positive Input Ventilation
Loft Mounted Positive Input Ventilation Unit with Heater


Positive Input Ventilation
Loft Mounted Positive Input Ventilation Unit with Heater & Advanced Control


Positive Input Ventilation
Loft Mounted Positive Input Ventilation Unit

What is Positive input ventilation?

Positive Input Ventilation (PIV) is a whole-house ventilation system that works by introducing fresh, filtered air into a building at a continuous, low rate.

This creates a positive pressure environment that pushes out stale air and excess moisture, helping to reduce condensation, improve indoor air quality, create a healthier living environment and has even proven to be an effective means for reducing Radon gas.

PIV systems are particularly effective in properties that suffer from condensation and damp issues. It can be installed in a variety of buildings including homes, apartments, and commercial properties.

What issues can positive input ventilation solve?

Excessive Moisture

Moisture is a common problem in residential properties, especially in areas with high humidity or poor ventilation. Excessive moisture can lead to condensation on windows, walls, and ceilings, which can result in mould growth and damage to the building fabric.

Poor indoor Air Quality

Indoor air quality can be affected by a range of factors, including inadequate ventilation, poor cleaning practices, and the use of certain products and materials. Poor air quality can cause respiratory problems, allergies, and other health issues.


Condensation occurs when warm, moist air comes into contact with a cooler surface, such as a window or wall. If left unchecked, it can lead to mould growth and damage to the building fabric.

Mould Growth

Mould growth is often the result of excessive moisture and poor ventilation. It can cause health problems, as well as damage to the building fabric.

Unpleasant Odours

Poor ventilation can lead to the buildup of unpleasant odours, which can make the indoor environment less comfortable and less inviting.

Keep it fresh

By introducing fresh, filtered air into the property, PIV can help reduce the concentration of moisture and pollutants, thereby addressing the issues listed above. PIV can promote a healthier and more comfortable indoor environment, reducing the risk of respiratory problems, allergies, and asthma. With PIV, occupants can enjoy improved air quality and more pleasant living spaces.

How does positive input ventilation work?

Positive Input Ventilation (PIV) is a simple and effective ventilation solution that works by introducing fresh, filtered air into a property.

The PIV system operates by drawing in air from outside the building, typically the loft where it can benefit from solar gain (making use of the warmer air within your loft space), filtering it to remove pollutants and allergens, and then gently circulating it throughout the property. This creates a positive pressure environment, which pushes stale, moist air and other indoor pollutants, such as mould spores, dust mites and volatile organic compounds (VOCs), out through natural leakage points.

This continuous process of introducing fresh air and expelling stale air not only improves air quality but also helps to maintain a healthy indoor environment, reducing the risk of respiratory problems and other health issues associated with poor indoor air quality.

Common PIV questions?

How much does a PIV unit cost to run?

PIV units typically cost less than £5 per year to run. You can use our running cost calculator for a more accurate cost.

Will a single PIV unit mounted on The landing cover all the home?

In the majority of standard properties up to around 150m <, a single unit will be enough. As part of the installation and as per the Part F building regulations, you should ensure Internal doors allow air to flow through the dwelling by providing a minimum free area equivalent to a 10mm undercut in a 760mm wide door.

The above combined with the centrifugal motor in our units, allows air to be pushed into all corners of the home.

Can a PIV unit help with indoor Radon concentrations?

PIV is a great way to lower indoor radon levels. Because PIV positively pressurises the home, flipping the normal pressure balance so that the air pressure inside the building becomes higher than that in the ground which will inhibit radon from being drawn inside.

Is a PIV unit suitable for a new home?

Newer buildings are more airtight and for these, we recommend an MVHR system over a PIV unit. A PIV unit works by pressurising the property and the contaminated air is pushed out through natural paths in the dwelling’s facade or window trickle vents.

If the property has air losses at or below 3m3 per hour per m², at a pressure of 50Pa, there would not be enough air leakage for the unit to work effectively.

Heaters in PIV units

PIV units can come with or without heaters, here are the most-asked questions.

Do I need a heater?

This really depends on where you live (because of your local climate) and the type of heating installed. The heater in a PIV is not there to fully heat the incoming air, only to temper it. Tempering the air removes the chill when it gets cold. In most cases, your household heating will do a more efficient job of heating the air that has come in when needed.

What temperature should it be set to?

While this is a personal preference, our units with heaters come set at 10°C from the factory. This is often a good balance between no chill and the average UK temperature meaning it does not operate (saving energy).

How much does a heater cost to use?

While we can tell you how many watts the heater will consume when it’s on, we can’t tell you the running cost because every installation is unique. Things that affect when the heater operates:

  • Location of the building in the UK
  • Position of your roof vs the sun and how much your loft space will warm from it.
  • The set point of the heater.
  • The size of the building and the l/s of air required to ventilate it.

Need help? Email or call the team on 01384 275771