Positive Input Ventilation

Positive input ventilation (PIV) is a whole-house ventilation system that gently supplies filtered fresh air into a home, usually drawn from the loft, to dilute moist air and reduce condensation, mould and stale odours. We currently stock the Manrose Lo-Watt Pivotal PIV unit.

PIV is a popular remedy for condensation in houses and bungalows with a loft space, used alongside room extractor fans. Buy at trade prices on account, with next working day delivery across Northern Ireland and the Republic of Ireland when you order in-stock items before 5pm, Monday to Friday.

MANPIVH Ships in 3-5 days

Manrose Lo-Watt Pivotal Positive Input Ventilation

£346.80 inc. VAT

Is positive input ventilation right for the property?

Condensation problems are often caused by moist air that has nowhere to go. PIV works by introducing a steady supply of fresher air, creating slight positive pressure that pushes humid air out through the building's natural leakage points and dilutes moisture throughout the home.

How a loft-mounted PIV unit works

The unit sits in the loft and draws in air, which is usually a little warmer and drier than outside air.
Air passes through a filter before being delivered through a ceiling diffuser, typically on a central landing or hallway.
It runs continuously at low speed, with fresh air spreading through the house as doors are opened and closed.

When PIV is a good fit

PIV suits houses and bungalows with an accessible loft where condensation, black mould on window reveals, or musty smells are an issue despite reasonable heating. It is not a replacement for room extraction: kitchens and bathrooms should still have suitable extractor fans to remove moisture at source. Flats without loft space may need a different approach, so check the manufacturer's guidance for your property type.

Installation points

Position the diffuser centrally so air spreads to as many rooms as possible, keeping it away from bedroom doors and smoke detectors as the instructions advise. The unit typically connects to a fused spur with local isolation; follow the manufacturer's instructions and current wiring regulations. Allow for the filter to be checked periodically. Ducting, grilles and other installation parts are available in our fan accessories, and you can compare all ventilation options in our fans range.

Buying from Meteor

Meteor Electrical is a family-run wholesaler based in Cookstown, Co. Tyrone, stocking 5,000+ products. Delivery is free over £30 / €35 ex VAT, with next working day delivery to NI and ROI and 3–5 working days to England, Scotland and Wales.

FAQ's Ask Your Own Question

What is positive input ventilation?: Positive input ventilation is a whole-house system that supplies filtered air into a property, usually from the loft through a ceiling diffuser. By gently pressurising the home, it pushes moist, stale air out through natural gaps and dilutes humidity, reducing condensation and mould. It runs continuously at low power.
How does PIV reduce condensation?: PIV reduces condensation by replacing moist indoor air with drier, filtered air. Loft air is often slightly warmer and drier than outside air, and introducing it steadily lowers the overall humidity in the home. With less moisture in the air, less water condenses on cold windows and walls, reducing the conditions mould needs.
Does positive input ventilation replace extractor fans?: No, PIV works alongside extractor fans rather than replacing them. Kitchens, bathrooms and utility rooms produce large amounts of moisture that should be extracted at source. PIV deals with background humidity across the whole house, while extractor fans handle the peaks from cooking and showering.
Where is a PIV unit installed?: A loft-mounted PIV unit sits in the roof space, with a ceiling diffuser positioned centrally, usually on the landing or in the hallway, so air spreads throughout the home. The exact positioning rules, including distances from walls and doors, are set out in the manufacturer's installation instructions.
Will positive input ventilation make the house colder?: In most cases the effect is minimal, because loft air is usually warmer than outside air and is delivered at a low, steady rate. Drier air also feels warmer and is easier to heat than damp air. In very cold weather, some PIV units adjust their speed or offer optional heating, so check the specification of the model.
Does a PIV unit need to run all the time?: Yes, PIV is designed to run continuously at a low speed so that it maintains steady air movement and humidity control. Units such as the Manrose Lo-Watt Pivotal are designed for low power use to keep running costs down. Switching it off for long periods allows moisture levels to build up again.