'Most issues we see in basements come down to poor or no ventilation,' reveal the experts — here's how to get it right

Getting basement ventilation just right is equally as important in an area that is going to be used solely for storage as it is for a new habitable space.

Basement conversions are one of the best ways of gaining extra living space without extending the footprint of a house, but there are a few key elements to get right if you want this type of project to be a success – good ventilation being one of them.

There are several different ventilation methods for basements to choose from so I asked the experts to explain how each works and what situation they are most suitable for.

How to ventilate a basement used for storage

There are several different ways you can ventilate a basement. The method you choose is partially dependent on your basement ideas. If you don't plan on using it as habitable space, things will be a little simpler.

'If it’s just a storage area and it stays bone dry, you might get away with passive vents,' explains Michael Zohouri, the founder of Pyramid Eco. 'That usually means air bricks or through-wall vents at opposite ends of the room to create some cross-ventilation. It’s low maintenance and doesn’t need electricity. But it relies on natural airflow, which can be unpredictable in a basement.

'When there’s no wind or it’s freezing outside, it doesn't move much air and can bring in cold drafts.'

Michael Zohouri

Michael Zohouri leads The Retrofitters as its founder, bringing over a decade of experience to the company. His expertise spans energy-efficient retrofitting projects, including insulation, solar, and heat pump installations. Committed to addressing challenges like thermal bridging and improving air quality, Michael focuses on creating healthier, more sustainable living environments while reducing energy costs for residents.

How to ventilate a basement for habitable space

If, like many others, you have decided to use your basement as additional living space, the ventilation provision you put in place will need to be a little more involved. Getting this wrong is one of the most common basement conversion mistakes.

'If your basement conversion is going to be used as a living space, then ventilation becomes non-negotiable. Otherwise, you’re asking for trouble,' warns Michael Zohouri.

'There are a few options – the right one depends on what you're doing with the space,' continues Michael. 'You’ve got extractor fans, heat recovery systems (MVHR), or positive input ventilation (PIV). Each has its pros and cons.'

'In the UK, basement ventilation typically falls into two types: passive and mechanical,' picks up Farook Member, director and home improvement expert at QS Supplies. 'Passive methods, such as air bricks or ventilation shafts, can of course get some air in and out, but usually not enough for sealed or converted basements.'

Farook Member

Farook Member is the director of QS Supplies and a seasoned expert in the home improvement and bathroom industry. With over three decades of experience, Farook has been at the forefront of innovation and quality since founding QS Supplies in 1990.

Passive stack ventilation

This is a natural – as opposed to mechanical – method of ventilation.

Passive stack ventilation relies on the natural upward movement of warm air to create airflow. Vents are placed at different heights within a building, which allows warm air to rise up and leave the space via higher vents, while fresh, cooler air is brought in through lower vents.

This method is especially effective in spaces with high ceilings or where there are significant temperature differences between the inside and out.

Extractor fans

Mechanical extractor fans, exactly like bathroom extractor fans or those found above a cooker, can be used to draw stale, moist air out of a basement.

'Extractor fans are good for removing moist air from bathrooms or utility areas, but they don’t bring in fresh air unless paired with trickle vents,' explains Michael Zohouri.

'Part F of UK Building Regulations specifically requires that all habitable rooms, including basements, must have an adequate level of ventilation,' adds Farook member. 'If natural ventilation is not achieving the required air change rates, then mechanical solutions will be necessary.'

Mechanical extract ventilation (MEV) systems

These systems are ducted and take air that is full of moisture up and out, while bringing fresh air in through trickle vents and air bricks. This would be a good option for basement kitchens.

'For most UK properties, the best route is mechanical ventilation, particularly for basements that are being used as living spaces,' says Farook Member.

In the case of MEV systems, these are a good way of addressing indoor air quality issues, controlling humidity and simply improving overall comfort. Additionally, these systems often have energy-efficient features, such as variable speed fans.

Mechanical extract ventilation with heat recovery (MVHR)

If you plan on using your basement to add space without extending, creating a completely new habitable storey, it is highly recommended that you consider installing MVHR.

These systems extract stale, moist-laden air and introduce fresh, filtered air back in through a heat exchanger. By extracting the heat from the air, none is lost.

'In higher-spec jobs, I often recommend MVHR,' says Michael Zohouri. 'It's a bigger investment, but it gives you constant fresh air, removes stale air, and recovers heat in the process. It’s the best option if you're converting the basement into a habitable space. It also helps with humidity and air quality, which people really notice.'

Positive input ventilation (PIV)

PIV systems are another type of mechanical ventilation and are perfect if you are looking for ways to prevent mould.

PIV units create positive pressure that displaces damp air through either natural or ducted openings.

'A unit in the loft gently pushes air through the house, including down to the basement if ducted correctly,' adds Michael Zohouri. 'It works well in some older homes where you need a whole-house solution, but it’s not suitable for every layout.'

'PIV systems are easier and much more affordable to install than MVHR,' says Farook Member. 'Plus they work well in older properties where some air flow is present.'

Which type of basement ventilation is best?

This very much depends on what you intend to use the space for, your budget and its current condition. One of the other things you need to know before converting a basement is the building regs requirements for ventilation.

For example, a space for storage only might be fine with a dehumidifier and natural ventilation, while one with a kitchen or utility will require some form of mechanical ventilation.

Basements are required to meet minimum air exchange rates in order to maintain indoor air quality. These rates vary depending on usage and space size.

'The biggest mistake I see is leaving ventilation until the end,' says Michael Michael Zohouri. 'By then, ducting is hard to route and the options become limited. It’s far easier and cheaper to get it right from day one, when you’re still framing out the space.'

FAQs

Why is basement ventilation important?

One of the most important elements of any basement conversion is home ventilation, and so it is crucial to understand why it needs to be done.

'Most issues we see in basements come down to poor or no ventilation,' reveals Michael Zohouri. 'If you’re using the space regularly, it needs fresh air, just like any other room in the house. Otherwise, you'll end up dealing with condensation, stale air or mould issues.'

There are other reasons why proper ventilation is important too. Not only does it remove stale air, but it also helps to maintain consistent temperatures, meaning the energy you use to heat and cool the area is reduced.

Additionally, basement conversion building regs also specify minimum ventilation rates – plus, without it, you risk radon seeping into the space, posing serious health risks.

What are the building regs for basement ventilation?

There are several different sections of the building regs that relate to basements, but when it comes to basement ventilation, you'll need to pay attention to Part F.

'Part F of the building regulations requires 'adequate means of ventilation' for any habitable space,' explains Michael Zohouri. 'If you’re converting a basement into a bedroom, bathroom or office, that definitely includes mechanical ventilation. Air bricks won’t cut it if you're putting in a bedroom or shower room.'

Will a dehumidifier help with ventilation?

Dehumidifiers are appliances that are designed to remove excess moisture from the air and maintain stable humidity levels.

They can help prevent damp, mould and condensation – some of the best dehumidifiers even feature laundry drying modes.

What dehumidifiers don't do is introduce fresh air back into the room.

As the colder months approach, investing in a dehumidifier is a great way to ensure you aren't battling window condensation and mould patches.

Make sure you know how to choose a dehumidifier that will be right for your space before parting with any money.