PIV Unit Guide – Everything You Need To Know.

Positive input ventilaiton

So you have a loft space and you have heard about PIV units? Well, if you want to make use of your loft and keep your home fresh and dry then a PIV unit is a must-have. PIV stands for Positive Input Ventilation, it was invented in the 70’s by Nuaire. This revolutionary device provides a steady supply of fresh air to the house via the loft. This fresh air cascades through the house replacing the old, stale and damp air. Consequently, excess condensation and damp are eradicated along with mould.

However, most people are struggling to understand what this gadget is and how it works. We have done some research and put together all the information you need to make an informed choice on getting a PIV unit.

What is a PIV Unit?

In simple terms, positive input ventilation (PIV) is a method of ventilation used to improve the house’s air quality. This device uses a fan to push out moist and stagnant air while replacing it with fresh, filtered and dry air. As a result, ventilation is improved around your home, thus curbing breathing problems and preventing property damage. Currently, over 1 million homes in the UK are fitted with PIV units! Some PIV units come with the option of warming the air as it is blown into the home. Because of this, you benefit from a warmer home as well as a dry one.

How Does a PIV Unit Work?

The principle behind the functionality of the PIV unit is the use of a small fan. This fan has various speed settings that can be altered according to the size of your home or the severity of any damp issues. Fan speed is selected on the PIV unit controller, air is then blown into the house from the loft. Most lofts are insulated in “breathable” materials which allows the PIV unit to draw fresh air from outside. There is no need to vent the unit externally as the natural breathability of your loft is all that is required. Please note some lofts are insulated by non-breathable materials, this would render the use of a PIV unit sub-optimal.

The PIV works by pumping this fresh air into your home. The process forces stale, damp air out of your home through gaps and vents, this greatly reduces the presence of excess moisture and thus reduces condensation. For maximum efficiency, the PIV unit should be hung at near ceiling height. If your PIV unit is well placed, then warm air which has risen into the loft will be recycled through your home. During winter, warm air which rises naturally will be recycled, saving you money on heating. You should also note that PIV units have large air filters to stop any dust or pollutants being circulated through your home. Replacement filters are relatively cheap and easy to fit.

How to Fit a PIV Unit

If you’re a person that loves DIY as many of us are, then the PIV is relatively easy to install. PIV units generally come with complete instructions to follow telling you how to do everything from setting up the sensors to installing it in the loft.

You’d need to cut a hole in the ceiling and put a mounting screw into a rafter nearby. The PIV unit generally comes with all the ancillaries needed to create the suspension installation. We recommend that you seek a profession electrician to help connect the device to the mains. This is for safety purposes as well as insurance integrity. We found an excellent video on how to install a PIV unit and have linked it below. It really is quite simple!

If you’re not a DIY person and feel that this is too much work for you to handle then no need to worry, you can look for a quality installer because you want your job done correctly.

There are plenty of options with companies out there, and you shouldn’t settle for one which isn’t excellent. You can research reputable companies online and read reviews to ensure they are top-notch.

You should call the companies and ask for their level of experience to see if they have experience with installing PIV units. A key point to note, though; Choosing a company with the lowest rates is not always the best option. You might regret it later.

Why Do You Need a PIV Unit

Studies show that activities such as cooking, cleaning, and bathing generate up to 12.5 litres of moisture per day. This amount of moisture can cause excess condensation and mould growth as a result. This can damage both your health and property

It is also known that fumes from detergents, gas outlets, paints and odours can pollute the air around your home. Given that a normal person breathes up to 11000 litres of air per day, good air quality is imperative. Poor indoor air quality can cause diseases such as asthma and other breathing system difficulties.

Further, most new homes are insulated from heat loss using modern materials. As well as preventing heat from escaping, these can also prevent moisture from escaping. Consequently, this leads to a buildup of moisture which precedes issues with condensation and mould.

The installation of a PIV unit can greatly increase indoor air quality and prevent many of these issues.

Here is a recap of why you might benefit from a PIV unit

  • They are economical as the units draw anywhere from 1.5 to 15 watts.
  • The units are relatively quiet and produce little noise.
  • Removes trapped odours and fumes.
  • Stops condensation.
  • Can be tamper-proof, an excellent option for the landlord.
  • The PIV unit works on the whole house, and so you don’t have to utilise damp busting methods in different rooms
  • It also filters the air and thus will remove dust, debris and any other stuff you do not want in the house.

How Much Does It Cost to Run a PIV Unit?

According to Local Authority Building and Maintenance (LABM); ‘On average a PIV unit will consume 5 watts of power which will cost just 1p a day to run. As a result, PIV systems have long been considered one of the most affordable ways to provide whole-home ventilation.’ Please be aware that a heated PIV unit costs significantly more to run. LABM states that ‘heated systems typically consume 500 watts of power (or 100 times that of a non-heated version) and running costs can be as much as £1 a day when the heater is enabled.’ We advise people to strongly consider whether you need a heated unit because of this fact.

A typical PIV unit costs around £300 and can last you roughly ten years running 24 hours a day. A non-heated PIV unit would cost roughly £36 a year in electricity. This makes a PIV unit extremely cost-effective. It would be cheaper to run a PIV unit than almost any dehumidifier!

Nuaire Drimaster PIV Unit Review

The Nuaire Drimaster is the first name that comes to mind when talking about PIV units. You can’t go wrong with the company that invented the technology in the first place. The Nuaire Drimaster has an added advantage of the system controls being located in the ceiling diffuser. This feature allows you complete control of the unit without having to enter the loft space. Further to this, a seven-segment display notifies you of the need for filter change and what setting the Drimaster is running on. You can alter the settings with the push of a button on the contemporary diffuser. The Nuaire Drimaster uses the principle of providing ventilation to the whole home via the loft. The process introduces fresh air while circulating movement of air in and out of the home.


  • 6 – year warranty
  • Easy installation
  • Low maintenance
  • Whole house condensation control
  • Low power consumption
  • Manual boost switch
  • Improves air quality


  • Not suitable for homes without lofts

Alternative to Nuaire Drimaster PIV Unit

Inventor Dehumidifier

This dehumidifier is a standard 12L dehumidifier currently on the market. It eliminates and extracts unwanted moisture at a rate of up to 12L per day while preventing mould and dampness. Whether it’s drying your laundry or removing moisture, the dehumidifier handles both while being energy efficient at the same time. The device features a timer for scheduled operation. Comes with a laundry mode for fresh and dry clothes, smart dehumidification, lower power consumption and energy savings. 

Inventor Fresh 12L/Day Dehumidifier

Digital Humidity Display, Silent, Continuous Drainage, 24Hr Timer, Laundry Drying, Aggressive Against Damp and Moisture, Eco-friendly

PIV units have incredible features and are a solid alternative to dehumidifiers when you have a loft space.

While the PIV unit is more of an up front investment, they are way less expensive to run than almost any dehumidifier.

You only need one PIV to ventilate the whole home. Whilst the Inventor Dehumidifier may be enough for one room or a small dwelling, it won’t cut it for large homes. The PIV unit is the superior choice for homes with a loft and are much more cost effective to run.


Do you require a professional to install your PIV unit?

If you are a DIY person and have a 1 amp fuse in the plug socket, you can comfortably plug it into a socket, but if you cannot, we would advise you to have an electrician do it for safety and insurance sake.

Will the PIV make the air warmer or colder?

A great answer for this is the air could be both – warm or cold. This is why – the air coming into your home will be cooler than that of what is inside your home. However, the loft will be warmer because of solar gain thus warming the air. If you want, you can purchase a heated PIV unit that will preheat the air.

Are PIV units loud?

No, unless you’re running on a high speed, you’ll barely hear it.

How will the air in my home escape?

There are numerous leakage paths for air to escape from your home. These include cat flaps, keyholes, gaps and cracks around doors, letterboxes, windows, floors and ventilation bricks.

Are PIVs expensive to run?

On average a PIV unit will consume 5 watts of power which will cost just 1p a day to run

Final Thought

If your beautiful home has a loft and is suffering from condensation, mould, odours or mildew, then the PIV unit might be your best bet to improve the air quality. Remember, stagnant air traps humidity and other harmful pollutants, good ventilation can ensure this doesn’t happen. If you’re finding it a bit confusing or difficult to choose the right brand, you can’t go wrong with the Nuaire Drimaster, it has it all and is a robust choice. It has easy installation, cost effectiveness, efficiency, durability, and not forgetting the outstanding warranty of 7 years. Investing in a PIV unit can be a cheap way of protecting your home and health for years to come.

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