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Detailed Overview of Positive Input Ventilation (PIV) Systems

Detailed Overview of Positive Input Ventilation (PIV) Systems
30 May, 2024

Detailed Overview of Positive Input Ventilation (PIV) Systems

How PIV Systems Work

Air Intake and Filtration:

1.       Source of Air: PIV systems typically draw air from the loft space or directly from outside. The loft air is often used because it is generally warmer and less humid than outdoor air, especially in winter.

2.       Filtration: The incoming air is passed through a filter to remove dust, pollen, and other airborne particles, ensuring that the air introduced into the living space is clean.

Air Distribution:

Central Diffuser: The filtered air is then distributed throughout the home via a central ceiling diffuser, usually located in the hallway or landing. This central position helps the air to circulate efficiently throughout the property.

Positive Pressure: The PIV system creates a slight positive pressure within the home, which helps to push stale, moist air out through natural leakage points such as cracks, vents, and gaps around doors and windows.

Humidity Control:

Dilution of Moist Air: By constantly introducing fresh air, the PIV system dilutes the indoor air, reducing relative humidity levels and helping to prevent condensation.

Evaporation: Over time, the lower humidity levels help to dry out existing mould and mildew, making it easier to clean and preventing regrowth.

Types of PIV Systems

Loft-Mounted Units:

PPS/L/H Loft Model DC Motor with Heater: This model includes a built-in heater to temper the incoming air during colder months, providing comfort without significant increases in heating costs.

PPS/L Loft Model DC Motor: Similar to the loft model with heater but without the heating element, suitable for properties where additional heating of the incoming air is not necessary.

Wall-Mounted Units:

PPS/W/H Apartment/Flat Model DC Motor with Heater: Designed for properties without loft space, such as apartments and flats. This model includes a heater to ensure the air remains warm and comfortable.

Benefits of PIV Systems

Health Benefits:

Improved Air Quality: By filtering out pollutants, allergens, and dust, PIV systems contribute to a healthier indoor environment, which is particularly beneficial for individuals with respiratory conditions such as asthma or allergies.

Mould Prevention: Reduced humidity levels prevent the growth of mould and mildew, which can cause respiratory problems and allergies.

Property Maintenance:

Prevention of Damp and Condensation: Lower humidity levels help to prevent dampness and condensation, protecting the property’s structure and reducing maintenance costs.

Preservation of Interiors: Preventing mould and mildew helps to preserve interior decorations, furnishings, and paintwork, maintaining the aesthetic appeal and value of the property.

Energy Efficiency:

Low Energy Consumption: Modern PIV units are designed to be energy-efficient, often using DC motors that consume less power.

Supplemental Heating: Units with built-in heaters use minimal energy to temper incoming air, which can be more cost-effective than heating the entire property.

Installation and Maintenance


Loft Installation: Loft-mounted units are installed in the loft space and connected to the central diffuser via ducting. This type of installation is relatively straightforward and minimally invasive.

Wall Installation: Wall-mounted units are installed on an exterior wall and may require a vent to draw in outside air. These units are suitable for properties without loft space.


Filter Replacement: Filters need to be checked and replaced periodically to ensure the system continues to provide clean air. The frequency of replacement depends on the air quality and manufacturer recommendations.

System Check: Regular checks of the system, including the motor and any heating elements, help ensure optimal performance and longevity.

Practical Considerations

Property Suitability:

Type of Property: PIV systems are suitable for a wide range of properties, including houses, apartments, and bungalows. They are particularly useful in older homes with poor ventilation.

Space Availability: Ensure there is adequate space in the loft or on walls for installation.


Initial Investment: The cost of purchasing and installing a PIV system can vary. However, the benefits in terms of health, property preservation, and reduced heating bills can outweigh the initial investment.

Vent-Axia Ltd and Nuaire Ltd both offer Positive Input Ventilation (PIV) systems. Vent-Axia, established in 1936, provides a range of loft and wall-mounted PIV units with features like advanced filtration, energy-efficient motors, and optional heating. Nuaire, founded in 1963, offers quiet and efficient PIV systems with good filtration and low energy consumption. Both companies offer reliable solutions to improve indoor air quality and manage humidity in homes.

Operational Costs: Running costs are generally low due to the energy efficiency of modern units.

By understanding these detailed aspects of Positive Input Ventilation systems, homeowners and property managers can make informed decisions to improve indoor air quality, reduce humidity, and maintain healthy living environments.

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