How green walls improve humidity levels: a comprehensive explanation

Green walls are becoming increasingly popular in offices, hospitality spaces, and residential areas, not only for their aesthetic appeal but also for their significant functional benefits. One of the most valuable advantages is their ability to increase humidity levels. This article explains how green walls contribute to a healthier indoor climate, which plants are most effective, and what factors influence humidity.

How does it work?
Green walls improve humidity through a process known as transpiration. Plants absorb water through their roots, transport it through their stems and leaves, and release it as water vapor through tiny openings called stomata on their leaves. This process can raise the humidity level in a room by an average of 5%, and in winter, this effect can increase to as much as 17%. The larger the green wall, the greater its impact on the indoor climate.

The impact of plant species on humidity
Not all plants contribute equally to humidity levels. Differences in leaf structure, water absorption, and transpiration capacity play a key role. Plants with large, thin leaves and active root systems increase humidity much more effectively than those with thick, leathery leaves.

Plants with high transpiration capacity
These plants actively contribute to increased humidity levels:

• • Spathiphyllum (Peace Lily): Known for its air-purifying qualities and strong transpiration capacity.
  • Chlorophytum (Spider Plant): Easy to maintain and proven to enhance humidity.
  • Nephrolepis (Boston Fern): A well-known plant for improving humidity levels.
  • Monstera (Swiss Cheese Plant): Its large leaves allow it to evaporate significant amounts of water.
  • Philodendron: With a robust root system and broad leaf surface, this plant effectively boosts humidity.

Plants with Low Transpiration Capacity
These plants contribute less to humidity but still offer aesthetic value:

• • Sansevieria (Snake Plant): Thick, leathery leaves release minimal water vapor.
  • Cacti and Succulents: These plants store water in their leaves and have low transpiration rates.
  • Bonsai Trees: Due to their limited leaf surface and low water needs, bonsai trees have a minimal impact on humidity.

Factors influencing the effect?
The impact of a green wall on humidity depends on more than just the plant species used. Environmental factors such as light, airflow, and the room’s climate also play a crucial role.

• • Light
    Light is essential for photosynthesis, which stimulates transpiration in plants. The more light plants receive, the more active the transpiration process becomes. In spaces with abundant natural light, the increase in humidity will be more pronounced.
  • Air circulation
    Airflow in the room (from fans or air conditioning, for example) helps to disperse water vapor more quickly, prompting plants to continue transpiring. This increases the green wall’s contribution to humidity levels.
  • Room Temperature
    Higher temperatures accelerate water evaporation. In a warmer space, plants will contribute more to humidity than in a cooler room.
  • Initial humidity levels
    If a space already has high humidity levels (e.g., a room with many occupants), the green wall’s impact will be less noticeable. Conversely, in spaces with air conditioning, where humidity is typically low, the green wall will have a much greater effect.

How much does a green wall increase humidity?
The exact effect depends on the size of the wall, the plant species used, and the room’s environmental conditions. Studies, including research from Wageningen University & Research (WUR), show that green walls can increase humidity by an average of 5% in office spaces with dry air. In winter, this increase can reach up to 17%. This difference is particularly significant in spaces with air conditioning, where the air is often very dry.

Example:

• • Small Green Wall (2-3 m²): Slightly increases humidity in small spaces such as meeting rooms or waiting areas.
  • Medium Green Wall (5-10 m²): Provides noticeable comfort in office spaces and public buildings.
  • Large Green Wall (>10 m²): Has a significant impact on humidity, especially in large open areas with dry air, such as shopping malls and airports.

Why Is Increased Humidity Important?
Optimal indoor humidity levels range between 40-60%. However, in many indoor environments, especially those with air conditioning, humidity often drops below 40%, leading to common issues such as:

• Dry eyes
• Irritated airways
• Dry skin
• Reduced comfort and productivity

A green wall can help alleviate these problems by naturally increasing humidity levels, offering a more sustainable and organic solution compared to mechanical humidifiers.

Would you like to learn more about how green walls can improve humidity or need advice for your project? Contact us for personalized advice and inspiration.