Positive Input Ventilation (PIV) Units vs. Extractor Fans: Choosing the Best Ventilation Solution

June 19, 2024

Air quality in your home is often an overlooked idea that is more important than you might realise. Maintaining good air quality doesn't just mean keeping your air clean, it's also helping to remove moisture to reduce mould and much more.

There are a few ways that you're able to reduce contaminants in the air, take the moisture away and overall improve the quality of the air in your home. Two of the most common ways to do this are to install extractor fans and/or positive input ventilation (PIV) units. Both options can work well together or on their own but sometimes one is more suited to your situation than the other.

These two options are very different but both help to achieve the same things using different methods.

Positive Input Ventilation (PIV) Systems

What is a Positive Input Ventilation Unit (PIV) Unit?

A positive input ventilation unit is designed to draw fresh air from the outside world and push it into your home. This air is then distributed throughout your home through ducting and into rooms and open spaces.

A PIV system is typically installed in your loft and will pull air in through the natural ventilation gaps in the roof and facias of your home. This air is then filtered to remove any contaminants and is pushed into your home.

Once this air has been pushed into the rooms in your house, the constant flow of air creates something called positive air pressure. This positive air pressure is created then more air is being introduced into an enclosed environment than is being expelled. This positive pressure helps to force the old air out of the house via natural gaps and ventilation that both old and new homes have.

What is the purpose of a PIV unit?

The whole point of a PIV unit is to introduce better quality air in your home, or indeed office. They're very popular for older. Older homes, on average, tend to be more susceptible to moisture and damp problems. This can be due to a number of reasons but most of them are age-related. However, newly built homes can also develop damp problems, often because of build quality issues.

In any case, if your home is suffering from dampness and moisture a PIV unit helps to circulate the air and push the moisture outside.

This is beneficial because it means that it's harder for mould and condensation to form around your home. Meaning that you can relax and not have to worry about how to deal with it.

Extractor Fans

What are extractor fans?

Extractor fans are commonplace in almost every home, it's quite rare to find a bathroom without one. Extractor fans are a localised solution to moisture and damp issues as opposed to a single unit to cover your whole home.

Extractor fans are designed to be placed in areas with the potential for high steam and moisture so that they can pull that moist air out of the room. This works by using a fan within the unit creating negative pressure in the room/ducting and taking the moist air outside.

This is often not a continuous function like the PIV units tend to be, an extractor fan will normally be turned off at the same time as your lights or after the built-in timer has reached its limit. However, you are able to purchase some extractor fans that contain humidity sensors which will tell the fan when to stop.

You have a number of extractor fan types to choose from including inline extractor fans, centrifugal fans and axial fans. Depending on the type of house you have there are a few different options that suit you best. You can also choose an extractor fan with a humidistat that will read the humidity levels and control things like fan speed and whether or not the fan should be on.

What's the benefit of an extractor fan?

One of the main benefits of an extractor fan is that the common units are cheaper when compared to a PIV unit. If you're purchasing a single unit (one PIV or one extractor fan) then you'll find that the extractor fan is cheaper. However, if you have a modern home with a number of toilets and you're looking for more high-end extractor fans, you may also find that the cost starts to add up.

Installation of an extractor fan tends to be a little easier, especially if you have an existing system in place. However, if you don't have an existing system and you need to fit ducting and other parts of the system you're likely to find it harder to install.

Choosing the Right Ventilation Solution

So now that you know a little more about PIV units and extractor fans you need to decide which one will be better for your needs.

There are a few things that you should consider to ensure that you make the best choice.

1. Purchase cost

The cost of buying a PIV unit versus extractor fans, PIV units typically involve a higher initial investment. PIV units are designed to provide whole-house ventilation, which means they have more complex systems and features, contributing to their higher cost.

On the other hand, extractor fans are generally more affordable and are designed for localised ventilation, such as in bathrooms or kitchens. While PIV units offer comprehensive air quality improvement and energy efficiency benefits, extractor fans are cost-effective for targeted moisture control and specific ventilation needs. The choice between the two will depend on the specific requirements and budget of the homeowner.

2. Running cost

When comparing the running costs of a Positive Input Ventilation (PIV) unit to extractor fans, PIV units are generally more energy-efficient. PIV units operate continuously, using a low-wattage fan that typically consumes a minimal amount of electricity, translating to lower ongoing costs.

In contrast, extractor fans are often used intermittently but can consume more energy per use due to their higher power requirements during operation. Over time, the continuous, low-level energy consumption of a PIV unit can be more cost-effective compared to the sporadic but higher energy use of multiple extractor fans, especially in homes with high ventilation needs.

3. Running noise

Running noise does sometimes play a big part in the type of extractor fan you choose or if you go with a PIV unit. Running noise refers to the amount of sound that the item makes while in use.

A PIV unit is in constant operation at a low speed and is designed to withstand continuous use. These units are generally quieter than an extractor fan and are usually installed in the loft. This means that any noise or vibrations are often absorbed before they're able to reach you.

However, the common extractor fan is a little louder and being that they're often surface mounted to your ceiling or wall the noise of more apparent. With that in mind, there are options that can help with this. You'll have the choice of an inline extractor fan which often sits in the ceiling cavity or loft which means the noise should be lessened. Or you should opt for a silent extractor fan, these are designed to be as quiet as they possibly can but can be more expensive than your conventional/common fans.

4. Control

Extractor fans typically allow for both manual and automated control over their operation. Using extractor fans with timers, humidistat fans and other features allows for automated operation. It means that you don't need to remember to turn them off with a switch and they can have a run-on time after you switch your lights off for example.

However, a PIV unit tends to operate on an automated basis. Constantly pushing fresh air into the property your PIV unit should be set up and automatically adjust fan speeds depending on humidity levels and other factors like that.

So should I get a PIV unit or an extractor fan?

PIV units and extractor fans work to create a similar outcome and are often bought for similar end goals, to reduce the chances on mould. However, they do it in very different ways and are suited to different environments.

Extractor fans are best for localised targeting, bathrooms, kitchens and wetrooms for example. PIV units are better suited for a property-wide application, reducing the chances of mould in and around most rooms in the building.

If you're looking for a more cost-effective option extractor fans tend to be the better choice. But be sure to calculate the number of extractors you need before making a choice. If you'd like a top-of-the-line extractor fan but you need 3-4 of them, you may find the cost adds up more than you realised.