Modular Green Wall Systems as a Specific Handwriting Style in Architecture of Green Buildings

1. Introduction

Nowadays, there has been a huge demand for harmony, balancing between the world created by nature and the non-natural world, created by man through building technologies. Young people generally do not have a need for nature, as they usually think, however, many people are latent biophiles. This is a confirmation of the habit of populating one’s home with an abundance of flower pots, listening to background recordings of the sound of birds or whales singing. Green plants also connect people with nature, thereby significantly reducing the pressure of the urban environment.

The biophilia as a term defined as “love to Life”. The most common approach in biophilic architecture is to implement natural elements into the buildings and spaces around it. If a person spends enough time among objects near nature, then you can relax and see your state of mind to spiritual harmony. Nature allows you to relax and calm down.

While green architecture focuses primarily on reducing the environmental impact of buildings through the use of sustainable materials, energy-efficient systems, and renewable energy sources, biophilic architecture focuses more on the human experience of the built environment, seeking to improve well-being and productivity by connecting people with nature. The characteristics of “nature” such as organised complexity, peril, improves building design [1].

It is acknowledged that green building technologies (GBT) include: green roof and green wall systems, net-zero energy and integrated renewable energy solutions, eco-materials for building construction and smart building management products. And, as we know, GBT as a complex is a perfect tool for the sustainable development in the construction. GBT innovations are highly valued, they are driving force [2].

As key elements of “carbon neutrality”, innovations in technologies of green buildings help enterprises to conserve and reduce energy expenditures [3]. Nowadays the building carbon emissions constitute a significant part of the total emissions. For example, in China these emissions exceed two billion tons, that is constituted 46.5% of the total emissions [4].

Rapid industrial development makes humanity think about the use of clean and green technologies now [5]. The indirect application of nature in biophilic architectural architecture is the development of new economic resources available to architects who use natural resources in their projects: stone, earth, plants, wood. If the workplace is filled with plants, then this will improve the mood and health of the worker, which will increase his productivity and creativity. Green plants are perfect means for cleaning of air pollutions.

Nowadays total population in urban areas is rapidly growing, and it is expected to increase up to 68% by 2050. The capabilities in adsorption of air pollutants, such as formaldehyde, benzene, xylene, are defined for the different plants.

Plants surfaces act as ‘living filters’, the study of Yang Han and Jechan Lee describes the differences in the removal efficiency of pollutants between the plant species [6].

Vertical alignment of green wall increases their potential for air purifying. The chlorophyll content [7] and various properties of the plants in response on the stress conditions were studied [8]. The scientists from Sydney, Australia, were looking for the special species, tolerant for use in in case of very high air pollution [9].

Green walls or vertical greening could use the various substrates from the loam soil to rice husk [10].

Among the new trends in green buildings - modular green walls, and they have a great potential. Modular green technologies and systems, including modular green walls, have a lot of benefits. One of the largest advantages of the modular green systems, that modules with a built-in vertical garden are easy to install and demount, because of their mobility and light weight. Also modules can be organized like a multi-variant nature, using free-form modeling and different textures, for example, it can make implemented the biophilic ideas of authors. So, as example, Grooflab, author’s project has surfaces with organic shapes - ocean waves forms. Nature-oriented urban design considers such projects with idea of biophilia because it is important to quality of our life [11].

Another benefit is possibility to integrate water irrigation system, both in each module and in the whole modular system.

Some researchers demonstrate the ability of modular green wall system (MGWS) to increase thermal insulation [12,13]. Thermal behaviour of panels with coconut fibre as an alternative core material to polyurethane was investigated [14]. In this regard, MGWS can reduce energy expenditure from the buildings [15,16].

Furthermore, the application of modern technologies such as smart buildings with combination of artificial intelligence and big data analytics is shaping the future trajectory of in the construction industry, including the influence on future generations [17,18,19,20].

Recent studies showed that MGWS could effectively reduce NO2, SO2, O3 and CO [21]. The major sources of air pollutants are building materials, chemicals and combustion by products, including carbon monoxide, nitrogen and sulfur dioxides, formaldehyde and tobacco smoke. Huge complex of chemicals, like benzene, formaldehyde, trichloroethylene, all potential carcinogens and irritants, harmful biological contaminants we exhale every day without even thinking about it [22]. So, released from foam, insulation, glues - formaldehyde is the cause of a great deal of coughing, allergic reactions, dizziness, etc. Carbon monoxide (CO) as combustion of all carbon fuels can lead to headaches, impairment of respiration, mental disorder, and in many cases very high concentration can cause death [23].

And what about air purifying plants? How do they behave? When air is polluted with such harmful substances as sulfur dioxide, hydrogen sulfide, ozone, nitrogen dioxide, ethylene, ammonia, heavy metals, acid aerosols, aldehydes, cement dust, pollutants cause acute and chronic damage to plant leaves - necrosis. Acute injuries are characterized by plasmolysis and death of individual cells, inhibition of individual tissue fibers. Chronic damage is characterized by a change in the color of the leaves of plants. So, when damaged by sulfur dioxide, whitening occurs, with ammonia - yellowing, hydrogen sulfide - “coffee” spots appear, ozone - dotted pigmentation of the leaves.

Green plants help human to feel at one with nature, we do not even notice, but they trap harmful substances from the air, thereby purifying it [24,25,26,27,28]. The leaves of plants, their roots, substrate filling and microbes work together to trap harmful substances: harmful pollutants are moved to the root zone, where they are processed (eaten) by microbes, which can use pollutants as a food source.

Species of plants that are most effective at removing all pollutants together – benzene (cancer-causing chemical), formaldehyde, trichloroethylene - are Bamboo Palm and English Ivy. Arrowhead vine, Chrysanthemums, Snake plant, Janet Craig, Massangeana (Dracaena) trap formaldehyde, benzene, toluene and xylene. Peace lily removes acetone, benzene, trichloroethylene and xylene. Gerbera Daisy is really good remover of benzene and absorbs carbon dioxide, which gives a lot of oxygen at night. Some plants, acting against common pollutants, may be toxic if touch it (or swallow): Rubber Plant, Leopard Lily [23].

In this study, various MGWS were analyzed to determine the most effective MGWS and the best plants, intended for them, for air purification.

2. Materials and Methods

MGWS (or green walls) differ from green facades in that the plants are rooted in a structural support that is attached to the wall. Many species and types of plants are tolerated the high life in a green wall, from herbs to grasses and ferns. Experimental tests can also help to analyze these systems in building structures [29,30,31].

Such systems can function both without water irrigation systems, and have built-in micro-drip irrigation systems, in which case water can be delivered from central water supply systems, or supplied from a special water tank where water is pumped with a pump, and then through pipes laid inside the green walls, goes to each plant. The unused water can be discharged through a special drain and, after cleaning, re-supplied for watering plants.

In this research we were estimated four modular green wall systems: Grooflab, Biotecture, Vertis and Scotscape. The detailed estimation is shown below.

2.1. Grooflab MGWS

The present MGWS, invented by authors, has unique configuration of the modules for urban spaces. Irrigation control systems and hydroponics in agriculture of greenhouses are technically successful commercial practices in many parts of our planet (Figure 1).

The biophilic design of invented green wall system is oriented on the «Love-to-nature» conception. Panels of green walls include special constructive elements, inspiring by Renaissance, based on the totality of measurements of simple forms that are found in nature: golden ratio, Divine proportion, ocean waves form.

These modules of green wall system have a biophilic design, associated with the golden ratio (see Figure 2 a,b). In addition, to options that are different in shape in plan, there is an option with an inclination relative to a vertical surface. For the design of the structure, the option with a slope was chosen, since changing the degree complicates the design - and if this design is feasible, then options without a slope are easily feasible, involving the golden ratio and Fibonacci series. This is pleasing to the eye when looking at a modern building.

2.2. Biotecture MGWS

The Biotecture green wall system is formed using modules each nominally 600mm x 450mm x 62mm constructed from Polypropylene. Plants, such as ‘Irish Green’, Convolvulus cneorum, Pachysandra spp. and etc, can use for this system. 60 plants per sq m. could be built-in this MGWS. Lightweight at 70 kgs per m2 fully saturated weight [32]. The design solution of this MGWS is given on Figure 3.

2.3. Vertiss MGWS

The Vertiss MGWS uses planting modules, made of HD-EPP, to create an interior living wall. This vertical green system contains the modules of 800 x 600 mm, for 16 plants.

The growing medium is organic - 30% and mineral - 70%. Irrigation system has water consumption of 2L/h. Special mosaic effect can be easily achieved over the entire MGWS [33]. The Vertiss MGWS is shown on the Figure 4.

2.4. Scotscape MGWS

The Scotscape MGWS is a light-weight, semi-hydroponic, modular system, which consists of supporting wall, sub-frame, multi-layer modules, irrigation and plants. One square metre of modules holds up to 49 plants in individual pockets. Each module incorporates a drip-line irrigation system, modules can be fitted to both flat and curved surfaces. Weighing of the fully planted and saturated system is less than 40 kg per square metre, without plants - 2.1 kg. The water irrigation cycles can be installed with a fresh water top-up or the tank can be filled manually. The system is designed for rapid installation by a small team, minimizing on-site disruption [34]. Scotscape modular green wall system is given below (Figure 5).

The three most popular on the market vertical greening systems and one system, developed by the authors were investigated. The quantitative analysis of the plants, fitted into each modular green wall system is given below (Table 1).

A comprehensive analysis of all modular green wall system according to several criteria, the most important for choosing a system, we showed in the Table 2.

Analyzing Table 1 and Table 2, we chose the best system from the presented sample. According to the criteria of weight, variability of the irrigation system, the ability to change the design - according to three of the 5 criteria, the best system is Grooflab. It should also be noted that the modules of this system can accommodate up to 45 plants per square meter, which is also quite a lot compared to competitors.

3. Results and Discussion

In this research we used the data of report of NASA [22] on the absorption of pollutants - benzene, formaldehyde, trichloroethylene, by different plants for a 24-hour exposure period in the Plexiglas chamber. We combined these data and get an approximate value of absorbed micrograms of three air pollutants in different modular green wall systems.

It is shown the calculations of three air pollutants removed in different modular green wall systems in figures below (Figure 6 a–c).

Based on the comparison and evaluation of all three comparative diagrams presented, it can be concluded that the Grooflab and Biotecture modular green wall systems are the best in absorbing all three harmful substances from the atmosphere, when using all of the listed plants. In addition, it creates a specific handwriting style in architecture of green buildings (Figure 7).

TSE is best absorbed by the following plants - 1. Gerbera daisy, 2. Marginata and Peace lily. Benzene is best absorbed by the following plants - 1. Gerbera daisy, 2. English ivy. Formaldehyde is best absorbed by the following plants - 1. Bamboo palm, 2. Dracaena Janet Craig. However, formaldehyde is not absorbed by Gerbera daisy at all, and Marginata and Peace lily, English ivy absorb it very little. Both Bamboo palm and Dracaena Janet Craig, to a small extent, in comparison with the presented plant analogues, also poorly absorb benzene and TSE.

Thus, when choosing a wall system, preference should be given to the best among analogues - Grooflab and Biotecture, and when using plants for such systems, combine 3-6 types of best air-purifying plants - 1. Gerbera daisy, 2. Bamboo palm, 3. Dracaena Janet Craig, 4. Marginata, 5. Peace lily and 6. English ivy.

4. Conclusions

Today, we know that biophilic architecture focuses more on the human experience of the built environment to improve well-being and productivity by connecting people with nature. Green wall plants reduce human stress, that was proved by idea of biophilia.

In the “age of consumption” and uncontrolled use of natural resources, the role of man in the conservation of nature and, in general, life on Earth is especially important for future generations.

We must very competently and rationally, and only if necessary, using the natural resources of our Green Planet, which are depleted hourly, including through the fault of man. We can reduce the maximum allowable human intervention in ecosystems, and at the same time help restore green spaces both in the natural environment - by planting trees, and in the urban environment, using greenery systems on buildings. And the role of plants in this case is to help us preserve nature.

Modular green wall systems for buildings are an advanced modern solution and a unique handwriting style in architecture of green buildings, the easiest way to help us get closer to nature and feel like a part of it.

We have found experimentally that systems - Grooflab and Biotecture are most effective modular green wall systems, with using plants - Gerbera daisy, Bamboo palm, Dracaena Janet Craig, Marginata, Peace lily and English ivy, and as a consequence – the more pollutants they can reduce.

While both approaches are important for creating sustainable and healthy buildings, biophilic architecture places more emphasis on the psychological and emotional benefits of connecting with nature. And, of course, we all need to create spaces that are not only beautiful and functional but also promote health and happiness for our future generations!