A clearer picture of indoor greening
While the benefits of urban greening outdoors are well established, the impact of plants inside homes, schools and workplaces has remained far less defined. To address this gap, an international team of 35 experts developed a ten-question assessment framework examining evidence across technical, microbiological, health, socio-economic and place-based dimensions.
The research also delivers the first structured comparison of 26 indoor greening systems – from simple houseplantsnt to engineered living walls – assessing how they affect key indoor environmental quality measures. The findings offer designers, architects and building managers clearer guidance on what works in real buildings, and where further evidence is needed.
Cooler, more comfortable spaces
The analysis shows that larger, well-designed indoor greening systems can make spaces feel up to two degrees Celsius cooler and more comfortable, even when actual air temperatures remain unchanged. By increasing humidity and influencing airflow, plants can improve perceived thermal comfort, particularly during warmer conditions.
Some engineered systems were also found to help reduce fine particulate matter and volatile organic compounds (VOCs), although their effectiveness depends heavily on factors such as plant density, lighting levels and overall system design.
Researchers also highlight emerging evidence that indoor greenery may enrich the indoor microbiome by introducing environmentally derived microbes – a development that could have implications for long-term health and resilience.
Infrastructure, not decoration
Professor Prashant Kumar, lead author of the study, founder of GCARE and leader of the GREENIN Micro Network Plus project, said:
“People spend around 90 per cent of their lives indoors, but surprisingly, we still understand very little about how indoor plant systems can reshape those environments. Our collaborative work shows that indoor greening can make a meaningful difference in certain situations – not just to how buildings feel, but to how they cope with heat, humidity and pollutants.
“But these benefits don’t happen by accident. They rely on using the right systems, in the right way, with the right lighting and maintenance. Treating greening as environmental infrastructure, rather than decoration, as well as filling substantial research gaps in the topic area, will be key to unlocking its full potential.”
Dr Tijana Blanusa, Principal Horticultural Scientist at the Royal Horticultural Society and co-author of the paper, added:
“Indoor planting is a fantastic way to bring the benefits of plants, and people’s interaction with them, into urban homes, schools and any other spaces where nature is not easily accessible. This paper lays strong foundations by providing evidence of the conditions needed to achieve the greatest impact on air quality, wellbeing and more.”
More real-world research needed
The study also makes clear that further investigation is essential. Many earlier experiments relied on unrealistic numbers of plants or controlled laboratory chambers that do not reflect the complexity of real homes and offices.
The authors call for long-term, in-building studies that consider lighting, ventilation, occupancy and maintenance – the everyday realities that determine whether indoor greening performs effectively over time.
The research forms a core part of GREENIN Micro Network Plus, led by GCARE in collaboration with the UK Centre for Ecology & Hydrology, and the Universities of Bath, Oxford, York and Cranfield. Funded by the Engineering and Physical Sciences Research Council (EPSRC), the project brings together universities, local authorities, environmental organisations and horticultural experts to explore how indoor spaces can be designed for better air quality, comfort and wellbeing in a changing climate.
