Indoor plants and green walls can reduce certain air pollutants by around 10-30 per cent, while some indoor greening systems could cut the energy needed to cool buildings in certain office zones by up to 27 per cent, according to an international review led by the University of Surrey.

In a study published in Eco-Environment and Health, a team of 35 international experts led by Surrey’s Global Centre for Clean Air Research (GCARE) reviewed several studies from across the world on the performance of indoor greenery.

They found that passive greening, such as potted plants and living walls, can help remove volatile organic compounds (VOCs) – gases released by everyday products including paints, furniture and cleaning products. However, systems that actively draw air through plants and their growing materials were often more effective overall at removing these pollutants under controlled conditions.

Indoor greening was also associated with temperature reductions of around 0.5-4.5 degrees Celsius around the plants, showing its potential to improve indoor comfort and reduce reliance on air conditioning.

While the evidence points to the many benefits of indoor greening, its effectiveness varies depending on factors like ventilation, lighting, plant species and the type of system used, making it important to understand which approaches work best in different environments.

The review identified opportunities to strengthen the evidence behind indoor greening, as a large number of the studies were conducted in laboratories rather than realistic conditions. Many involved small test chambers and short monitoring periods, which may not capture how plants perform inside real-world environments and over time.

Professor Prashant Kumar, Founding Director of GCARE at the University of Surrey and lead author of the study, said:

"There is growing evidence that indoor greening can improve the spaces where we live and work, but much of the research has looked at individual benefits in isolation.

"What we've done is bring that evidence together and look at how we can better measure and predict these effects, including how they might change under different environmental conditions. While substantial research gaps remain, this provides a preliminary benchmark for making informed decisions about where and how indoor plants can be most effective."

The team also highlighted the need to better understand how outdoor conditions and climate change could affect indoor greening, particularly during periods of extreme heat and humidity, when poorly managed moisture levels could increase the risk of condensation or mould.

To help address these gaps, researchers proposed a conceptual framework combining monitoring and numerical modelling to assess how indoor greenery performs under different environmental conditions, with the aim of informing future building design, management and policy decisions.

Dr Elisa Valentim Goulart and Dr Hao Sun, both researchers at GCARE, added:

“The review highlights a substantial gap in the monitoring and modelling of indoor greening impacts, and further research is needed to address this."

The research was developed through the UKRI-funded GREENIN Micro Network Plus (UKRI1239), led by Professor Kumar at the University of Surrey, which brings together international expertise to advance research into indoor green infrastructure.

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