What causes the problems?

Did you know that 58% of people have suffered mould and condensation in their home? If you consider the fact that 90% of the time is spent indoors, it is vitally important to focus on improving indoor air quality (IAQ). It can damage not just property, but health as well.

Cooking, cleaning and bathing

These activities generate up to 10 litres of moisture per day. In addition, every load of washing that is hung to dry inside adds an additional 2.5 litres. All together there could be 12.5 litres of moisture generated in your home every single day which can cause condensation and mould.

Volatile organic compounds

Substances like formaldehyde get into the home from things like paint, new furniture and cleaning products. The average person breathes 9,000 litres of indoor air each day so poor indoor air quality (IAQ) can cause serious risk to health such as heart and respiratory diseases with asthma being a key concern.

Increased insulation

In the drive to insulate our homes we have created an airtight box where, not just heat, but moisture and chemicals can’t escape. This causes poor indoor air quality which can contain a cocktail of over 900 chemicals, particles and biological materials having a negative effect on health.


What is Positive Input Ventilation (PIV)?

Positive Input Ventilation (PIV) is an energy efficient method of pushing out and replacing stale unhealthy air with drier fresh air by gently introducing filtered air into the home and increasing the circulation of fresh air around the property and improving the indoor air quality (IAQ). 

Ventilation is condensation and mould’s biggest enemy as it removes the root cause: the moisture in the air. Mould is a simple plant; if you want to kill it, stop watering it. If mould has already formed, painting over it will not solve the problem. By removing the moisture and other pollutants from the air, condensation cannot settle and mould cannot grow which removes the problem at source.


The Solution

Positive input ventilation (PIV) brings one of the best solutions to tackle poor indoor air quality (IAQ). It is a solution for all types of properties, PIV units are usually situated in a loft or on a wall. Our PIV range offers both solutions whether you live in a house or a flat.

PoziDry Pro™ / PureAir Home
For properties with a loft

The unit can be hung from the rafters or mounted on the fully adjustable, anti-vibration feet to find the perfect loft location.

The optional F7 filter will remove almost all pollen from the air and help reduce diesel particulates.

With noise levels as low as 9dB(A) in the home, the unit can hardly be noticed when installed


Lo-Carbon PoziDry Compact Pro
For houses without a loft and flats


The PoziDry Compact Pro is a small unit that can be installed almost anywhere, even boxed in entirely along with the ductwork, to provide a discreet and unobtrusive solution.

replaced filter

The product’s unique G4 or F7 filter choices make improving indoor air quality easy.


The unit comes with 2 blanking plates and 1 grille with adjustable airflow direction.

Find out more about the products


Watch a video

Read the PIV range brochure


Product features comparison

Range Stock Ref. Loft Mounting Wall Mounting Heater Data Logger 3 Storey Compliant Buy Now
PoziDry Compact Pro™ 479188    
PoziDry Pro™ 476310      
PureAir Home 479090        

Frequently Asked Questions

Positive Input Ventilation is a process which dilutes, displaces and replaces unhealthy air in our homes with clean, fresh and filtered air. Comfort heaters can also be added to preheat the air if required. The ventilation air is delivered into a landing our hallway. It then gently ventilates all other rooms directly off the landing/hallway.
Vapour pressure will move air in our homes without us noticing. The most common causes of air movement are when we open a bathroom or kitchen door after bathing or cooking. The pressure caused by heat will look to equalise across the new volume. So moisture generated in bathrooms can end up in bedrooms. This can lead to mould growth.
It is unlikely increase the pressure because even refurbished homes that follow the latest guidance will leak air. A typical 3 bedroom home will leak at around 30 litres per second. The supply air from the PIV unit would normally be introduced at 21 litres per second. So it would be like trying to blow up a balloon with a hole in it.
There are numerous leakage paths for air to escape from in our homes; such as letter boxes, key holes, trickle vents in windows, cat flaps and gaps and cracks around doors, windows and floors.
The fan motor typically consumes about 5 Watts of power. Over a year this would cost around £7 or less than 2 pence a day.
The heater activation point can be set easily by your ventilation specialist installer. They are normally set a 10⁰C. The heater element heat up and transfer the heat to the incoming air. Although you cannot see it happening they are a little like oven thermostats and are not drawing power all of the time. They typically activate between 5% and 10% of the time. The cost over the heating season would be between £20 and £40 or 11p to 22p per day.
The Building Research Establishment tested Positive Input Ventilation and concluded that compared to extract fans with the same flow rate, it could save up to a maximum of 10% of the space heating costs. Compared to extract fans which take air out and this air is replaced with air directly from outside at outside temperatures. PIV draws air through the loft space. Even with the PIV unit running the Building Research Establishment found that our loft spaces are around 3⁰C warmer than outside. This is more energy efficient than air directly from outside.

What customers are saying

We think it is an absolute no-brainer – the Vent-Axia Pozidry Compact beats (The Competition) hands down in our opinion."

Mike Davison, preservationshop.co.uk

We’ve been using the PoziDry Compact Pro since its launch, and it’s working very well for our customers – it’s proving to be a very good product."

Property Services, B3Living

The improvement of our indoor air quality is noticeable. We haven't had drippy window since we've installed this.

Satisfied Homeowner