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How much impact do plants actually have on our air quality?


It’s long been thought that plants act as a natural air purifier, absorbing harmful chemicals in our homes and other buildings. However, a new report suggests that if we want to breathe in cleaner air, it might not be as simple as filling your home with some extra greenery.

Scientists from Drexel University in Philadelphia found that people would need up to 1,000 plants per square metre to get the same ‘air cleansing’ affects as opening a few windows. One of the researchers said: “Plants are great, but they don't actually clean indoor air quickly enough to have an effect on the air quality of your home or office environment.”

So, is it still worth having plants in the home, and how can we design and build homes to improve indoor air quality?

Air quality, health and the popularity of plants

Poor indoor air quality is known to contribute to health issues such as weight gain, depression, autoimmune and cardiovascular diseases, as well as impacting our cognitive performance.

Although the scientists from Drexel University may have put a question mark over the effectiveness of plants as air purifiers, it’s unlikely to reduce the popularity of foliage in the home.

Indoor plant sales boomed in 2019, with 67 per cent of Londoners purchasing a plant in the last 12 months. Search online on retailers’ websites, and you’ll find many ranges of flora and fauna promoted for their ‘air purifying’ benefits. But people’s growing passion for plants goes beyond the possibility of them absorbing chemicals and gases. Design trends, urbanisation and the feel-good factor associated with nurturing a living thing have all contributed to the increase in sales.

And these wider benefits of plants are something architects, property developers and interior designers need to bear in mind when it comes to creating homes that improve our lifestyle and wellbeing. The importance of incorporating biophilia into the modern building design has been well documented, but if plants aren’t particularly effective when it comes to cleaning our air – what else can we do?

MVHR systems and air quality

Air pollution in general is a growing concern – it causes illnesses, costs money and can even kill. And while we may associate air pollution with the likes of exhaust fumes from traffic, some studies suggest that the air inside our homes could be worse than the air outside thanks to things like cooking fumes, paints, fabrics, and cleaning products.  

To achieve better air quality in the home and other buildings we need the right design, ventilation (natural and mechanical), and building materials.

Mechanical Ventilation with Heat Recovery (MVHR) helps to minimise the amount of heat lost through ventilation, which can make up to around 30 per cent of the heating demand on a property. It is effective in providing the required amount of fresh air into a room to continually improve air quality levels to make sure they have a positive impact on the occupiers’ health and wellbeing, while simultaneously extracting stale and polluted air.

So, while architects and builders should bear the biophilic features of plants in mind when considering homes of the future, there are tools available, such as MVHR systems, that can be put in place to improve air quality without the need to create an entire green house to actually deliver some benefit.

However, MVHR only performs to its maximum potential if homes are built for ultimate energy efficiency. While MVHR systems are compatible with both new builds and refurbishments, they perform best when installed in homes that have high air tightness levels; essentially, the more sealed the property, the more effective the heat recovery system will be for its occupants.  

A 2017 report from the National House Building Council on MVHR best practice showed that, at that time, nine out of ten MVHR systems installed in homes had to be recommissioned or completely replaced, due to issues with ducting, insulation and changes made to air inlet valves. Since then, there has been a huge focus on building energy efficient homes, which contribute towards improving indoor air quality.

However, it’s truly only possible to achieve high indoor air quality with an effective MVHR kit, using the right grade of filters, which reduce and remove these pollutants and particles from entering the home.

While doing this may well have a more positive impact on cleaning the air than a house filled with plants could, adding greenery and nature into design still has other benefits.

For more information, check out our ultimate guide to indoor air quality and air pollution.

Ieuan Compton
Ieuan Compton Head of Marketing Services
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