If you have never heard of positive pressure ventilation (PPV) systems, they are an easy way to replace the moist air in a property with fresh filtered air.
The reason why PPV systems have grown in popularity is down to the development of new houses – but they can be installed in older properties too.
That’s because modern homes have been made more airtight to help with keeping them warm in winter, but this then leads to issues with condensation, mould and damp because there is no air flowing through the property.
So what is positive pressure ventilation in buildings, how does it work, and what are the benefits? Let’s find out in more detail…
What is positive pressure ventilation in buildings?
To help boost – or create a flow of fresh air – a positive pressure ventilation system will provide that continuous ventilation within a home without creating a cold draught.
The system itself is straightforward to install and consists of a small fan that is placed in the loft space which will force fresh, filtered air through the property using ceiling vents.
This forced air will then push the stale air through the gaps around windows and doors and other areas where the air will leak from a property.
The system works more efficiently when doors and windows are closed.
By removing this stale air, homeowners will then prevent the build-up of condensation and restrict the growth of black mould.
One example of a positive pressure ventilation system is the Drimaster DRI-ECO-HC Condensation Ventilation Loft Unit:
- Basic Hall Control Unit
- For homes with lofts
- Whole House Condensation Control
It has been highly rated by users and comes with a hall control and a seven-year warranty.
An alternative is the Nuaire Drimaster Eco heat condensation control PIV bundle which comes with a hygrometer to measure the level of water vapour in the air of the property:
- Drimaster Eco Heat with 400w integral heater. Compatible with optional controllers and sensors. Free i-sells digital hygrometer included.
- For homes with lofts for whole house ventilation. Complete with a FULL 7 Year Nuaire warranty.
- Supplied with all required parts for installation, no additional ducting required.
How positive pressure ventilation works
The important aspect of a positive pressure ventilation system is that it will draw in fresh air from outside the property, and then ‘dry it’ to an ambient temperature.
The system then gently pushes the clean air using the fan system throughout the home.
However, depending on the property, a PPV may not be the best solution for those homes with mould and damp problems.
That’s because the success of the system’s installation will depend:
- On the fan’s performance
- The building’s airtightness
- The distribution of ceiling vents
So, for a property that is particularly draughty, a PPV will struggle to force the dry, ambient temperature air into the rooms so any moist air already in there may remain.
Also, the roof space will need to be sealed properly so the air that has been forced through the property is not then moving to the loft space where it could be re-circulated.
If that happens, it will defeat the object of having a PPV installed.
It’s also worth mentioning the issue of negative pressure ventilation in a home.
An example of this would be an extractor fan, usually located in a bathroom or kitchen, and they suck air from a property, rather than pushing it in.
This then leads to negative or low pressure in the property – and the higher-pressure air outside the home will then be drawn into a property via the gaps, such as those around the windows.
Reasons a PPV might be needed
One of the big issues for modern house design is the lack of adequate ventilation because this leads to a build-up of excessive moisture and humidity inside.
Home dampness may be caused by various factors, including condensation. In an article by Sample (2023), he determined that damp appears when condensation occurs from the air moisture to the “colder surfaces”, and when water enters the house through various means such as through window cavities.
Damp invites bacteria that can trigger allergies and pose a danger to the health of the inhabitants.
In turn, this could lead to serious health issues for those suffering from allergies or asthma as the condensation then creates damp and black mould.
The damp and mould may appear on cold surfaces such as windows and walls and lead to black mould growing in damp areas, such as the kitchen or bathroom.
In a modern home, having effective ventilation is crucial and the PPV system will be designed to help improve the flow of fresh air.
This is further supported by Wolbrink (2009) as he explains the science behind mould and introduces the concept of psychometrics, which is the science of air containing moisture.
A combined understanding of the two provides insight to property owners such as construction, residential design, ventilation, and operation which could be effective for controlling mould growth.
The other big takeaway from installing a PPV system is that it should not be seen as being the best solution to a damp problem – that depends on the age and design of the property.
We mention below a potential alternative, however, the PPV system may prevent the build-up of mould in most properties.
Benefits of positive pressure ventilation systems
There is a range of benefits to using a positive pressure ventilation system, including:
- It will remove moist air to prevent condensation
- It will prevent black mould and musty smells
- The system will be low maintenance
- The system filters have a large capacity for maximising ventilation
- A PPV system will improve your home’s air quality
- Homeowners can preset the PPV settings to suit them
- Some systems have pre-heat facilities to maintain comfort levels – which helps with the heating bills
- The airflow will be consistent when the system is in use
- Improved ventilation can help those with allergies
Still not sure? There are more good reasons for installing a PPV system, including:
- It’s are cheap to buy
- It won’t need lots of ductwork
- It’s easy to install – althoug it should be done by a professional
- It’s cheap to run
- It’s very quiet
Disadvantages of a PPV system
Frankly, there are hardly any disadvantages of having positive pressure ventilation in your house, which is quite rare.
The only thing we would say is that it can make your home colder. That’s because in winter, you are blowing cold air into your house.
Unless you invest a bit more money for a PPV that preheats the hair before releasing it into your home. Ours preheats the air to 10°C (50°F), but that’s not particularly warm in winter.
As a result, the room with the vent is the coldest in the house in the colder months. And it also has an impact on the temperature of the whole upstairs, as it lowers it by a degree or two.
That’s something to keep in mind when deciding to get a PPV system.
Different types of positive pressure ventilation systems
Usually, a positive pressure ventilation system will be installed in the loft and then have an air diffuser ducted to it.
Some systems have a pre-heat facility so that the air is warmed up before being pushed down through the air vents.
For flats, where there is not a loft space, a convenient wall with a duct air intake point is a possibility.
The flat owner will need to duct the system to an outlet grille to help distribute the air evenly throughout their property.
PPV systems are suitable for most properties
Generally, a positive pressure ventilation system can be installed in most properties – though you need experts to do this and access to an exterior wall.
It’s important to get a qualified electrician to install a PPV system to make sure all is done according to regulations.
For some new build properties, a PPV may not be the ideal solution. It may be worth looking at a mechanical ventilation and heat recovery (MVHR) system instead. These won’t be forcing cold air into what is a warm home.
One issue for those homes built before 2010 is that they do not suffer from condensation as modern homes do.
That’s because they weren’t built to be airtight, so the building itself does the job of the PPV system.
Modern homes tend to be well-insulated and airtight, so owners of older homes will seal the gaps in wall cavities, roof spaces and window frames.
That will keep the heat in a home and reduce draughts.
The downside is that the moist air that is in the property will not have the opportunity of escaping, and it is this that will cause condensation and create black mould.
That’s when a PPV system can help to regulate humidity levels in an older home.
Not every home is suitable for PPV
Flat owners need to be careful where their PPV unit is installed. You will need a specific wall-mounted unit, and these usually have an in-built heater and a range of running speeds.
It’s worth highlighting that the first downside of seeing heating costs rise also means that simply opening a window to reduce condensation will also make a heating system work harder to heat the property.
Why a PPV system is worth the money
For anybody who is experiencing problems with persistent black mould and condensation in their home, then a positive pressure ventilation system could be the answer.
Homes that have ventilation systems installed in them showed reduced risk to health (Wargocki, 2016). Ventilation rates connected to particular health risks include asthma, airway obstruction, allergy, and SBS symptoms.
The study also shows that with ventilation systems, moisture levels are reduced, which also limits the growth of house dust mites.
Generally, increasing the flow of clean, fresh air throughout the property and removing stagnant air will improve air quality and reduce condensation.
PPV experts highlight that for those homes struggling with condensation problems, your rooms will be transformed between four and six weeks after having a system installed.
You can also use thermal lining paper for extra impact, as we did in our Wallrock thermal liner review.
This means that for a relatively inexpensive outlay, your property will be condensation-free with healthy air for those living there to breathe.
And for many people, understanding how positive pressure ventilation works in their home could lead to a reduction in black mould and condensation and boosting the air quality will be reason enough for making an investment.
Our recommended Positive Pressure Ventilation systems:
- Basic Hall Control Unit
- For homes with lofts
- Whole House Condensation Control
- Drimaster Eco Heat with 400w integral heater. Compatible with optional controllers and sensors. Free i-sells digital hygrometer included.
- For homes with lofts for whole house ventilation. Complete with a FULL 7 Year Nuaire warranty.
- Supplied with all required parts for installation, no additional ducting required.
