Studies and scientific evidence inherent in the world of living vertical gardens

Side by side withITC-CNR

Over the years, we have commissioned 3 scientific studies from the Institute for Construction Technology (ITC-CNR). These studies, together with several international studies, have shown that a Vertical Garden contributes positively to:

Improving air quality

Mitigating acoustics

Increasing psychological well-being

 Indoor air quality

In recent years, the design of increasingly high-performance buildings has led to a decrease in natural ventilation solutions, increasing energy consumption and contributing to Sick Building Syndrome (SBS). The integration of Vertical Gardens can reduce the operating hours of mechanical ventilation systems, improving air quality without a significant increase in energy costs.

Reducing CO2 levels

  • An experimental campaign was conducted in a confined and controlled environment (test cells) aimed at verifying the absorption-abatement capacity of indoor CO2 concentration by an Indoor Living Wall.

    • With average indoor comfort temperatures of 18-23°C, the Indoor Living Wall during "daytime" hours absorbs CO2 very efficiently, while reintroducing a limited amount back into the room.

  • The results make it possible to highlight the CO2 absorption capabilities of an Indoor Indoor Living Wall as a function of the indoor room temperature set-point, and thus to elevate this technology from a "furnishing" element to a system to be integrated at the design level for optimization of indoor air quality and reduced use of mechanical ventilation/renewal systems.

VOCs and PM uptake

  • As a partner within the ITC-CNR I-ZEB project "Toward Intelligent Zero Energy Buildings," an experimental campaign was conducted in a confined and specially prepared environment. A network of sensors was thus able to monitor the trend in concentrations of volatile organic compounds (VOCs) and particulate matter (PM) in the presence of a Vertical Garden intalled for experimentation.

  • VOCs analyzed:

    • Formaldehyde: a common compound derived from building materials and furniture.

    • Benzene: often found in combustion products and some plastics.

    • Toluene: used in paints and adhesives.

    • Xylene: derived from solvents and industrial chemicals.

    PM analyzed:

    • PM10: particles with an aerodynamic diameter of less than 10 micrometers, which can be inhaled and deposited in the upper respiratory tract.

    • PM2.5: particles with an aerodynamic diameter of less than 2.5 micrometers, which can penetrate deeper into the lungs and circulatory system.

  • The vertical garden demonstrated a significant ability to reduce the concentration of VOCs in indoor air. In particular, the following results were observed:

    • Formaldehyde and Benzene: Significant reductions due to the ability of plants to absorb and metabolize these compounds.

    • Toluene and Xylene: These VOCs also showed a decrease in concentrations, although to a lesser extent than formaldehyde.

    Regarding particulate matter:

    • PM10 and PM2.5: The living wall helped reduce particulate matter concentrations in indoor air. The plants and substrate of the vertical garden act as a natural filter, capturing suspended particles.

  • The vertical garden has proven effective in absorbing both VOCs and PM, improving indoor air quality and contributing to a healthier environment. However, effectiveness depends on the density and variety of plants used, as well as proper management of irrigation and ventilation.

Perceived air quality

The I-ZEB project also highlighted several positive aspects regarding the perceived air quality in the presence of the Vertical Garden:

  1. Improved perception of air quality: occupants reported a feeling of fresher, cleaner air inside the building.

  2. Reduction of unpleasant odors: plants in the Vertical Garden helped absorb volatile organic compounds (VOCs) and other pollutants, reducing the presence of unpleasant odors.

  3. Positive effect on well-being: users perceived an overall improvement in environmental comfort, which positively affected their well-being and productivity.

These results suggest that the integration of natural elements such as Vertical Gardens can have a significant impact on perceived air quality, improving the comfort and well-being of occupants.

For further evidence and insights on psychological and cognitive aspects, please refer to a specific bibliography.

Indoor acoustic mitigation

Acoustics is a key issue in building design, affecting the comfort and well-being of occupants. In densely populated urban environments, external noise can impair quality of life, making it essential to adopt effective solutions for sound insulation and absorption.

Recently, the integration of natural elements, such as Vertical Gardens, has been shown to improve the acoustic performance of buildings. These systems not only beautify spaces, but also help reduce noise and improve air quality, creating healthier and more comfortable environments.

Acoustic performance

  • Sound absorption measurements were carried out in a reverberation chamber according to UNI EN ISO 354. The results showed that the presence of water did not significantly affect sound absorption, while the plants improved performance, particularly those with small leaves. After two months in the ZEB, the absorption of the Vertical Garden remained almost unchanged.

  • Sound insulation tests were conducted in the ZEB laboratory, using the Vertical Garden as an additional layer between two rooms. The measurements followed the UNI EN ISO 16283-1:2018 standard. The installation of the vertical garden improved the apparent soundproofing power of the partition wall by 6 dB, with a significant improvement at medium-high frequencies.

  • Reverberation time was measured to evaluate the effect of the Vertical Garden on sound absorption in the environment. The measurements, conducted according to UNI EN ISO 3382-2, showed a reduction in reverberation time below 200 Hz and above 400 Hz, improving sound absorption in the environment.

  • The installation of the Vertical Garden improved sound insulation and reduced reverberation time, helping to optimize the acoustic conditions of the room. These results highlight the effectiveness of the living wall in improving acoustic performance, making it a viable solution for improving acoustic comfort in indoor spaces.

Legal requirements

  • The installation of the Sundar Vertical Garden has improved the sound insulation of the partition wall, and this has made it possible to meet the legal requirements of sound insulation of partitions between different building units, established by DPCM 05/12/1997. This requirement stipulates as a limit, for rooms used as offices, R'w ≥ 50 dB.

  • The presence of the Sundar Vertical Garden has improved sound absorption in the environment in which it was installed, allowing it to meet the optimal reverberation time for offices, defined by the Italian technical standard UNI 11532.

Outdoor acoustic mitigation

Another study explores the use of Vertical Gardens as an acoustic mitigation solution in urban facades. The goal is to reduce road traffic noise through sound absorption and scattering, with measurements taken in a reverberation chamber.

  • Measurements were conducted according to ISO 354 in two campaigns, in 2022 and 2023, with plants at different growth stages. The results show a reduction in absorption in the most recent measurements at the 200 Hz and 250 Hz bands.

  • Scattering properties were evaluated in 2023 using ISO 17497-1. The measurements were performed on a rotary table, and the results indicate that the values are usable between 100 and 400 Hz, extending up to 630 Hz in simulations.

  • GV is applied in urban settings to benefit from its absorption capabilities. Three scenarios were simulated: reflective facades, one facade with Vertical Garden, both facades with Vertical Garden. The results show an average sound level reduction of 3 dB for one scenario and 4.4 dB for the other, compensating for reflections typical of an urban canyon.

  • The use of Vertical Gardens in urban settings represents a promising solution for noise mitigation, demonstrating effectiveness in both absorption and acoustic scattering. Simulations indicate that the integration of Vertical Gardens into building facades can significantly improve the acoustic quality of urban environments.

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