Biophilia as a way to control indoor climate for human comfort Biophilic strategies for comfort and wellbeing
21 september 2020

Growing research supports the inclusion of nature into the built environment, however yet little detailed guidance exists on how to strategically integrate nature to maximize its benefits for human comfort!

Several studies have shown that biophilia can change human attitude, behaviors and positively reduce the so-called ‘Sick building syndrome’, whereby people suffer from health symptoms linked to the buildings in which they spend time. Evidence of these relationships is stronger for some aspects rather than others, as ongoing research has currently been carried out in this field.

The WUR (Wageningen University and Research Centre- Netherlands) has conducted several researches on the effects of plants on human beings and their findings span from mood alteration to physical improvements in people with prolonged exposure to living plants. The health benefits that have been monitored are lower blood pressure, increased productivity in the workplace, reduced anxiety levels, and increased alertness. Moreover, these health benefits are enhanced when there is an active interaction with vegetation, for instance by actively caring for them, planting, and irrigation activities. The study suggested, however, that research is still in its infancy and more evidence is necessary for this field to identify the exact factors that make working/interacting with plants beneficial for human wellbeing.

On a higher note, improvements of cognitive functions, productivity, creativity, and wellbeing of occupants have been found in projects that integrate these measures into the spaces as per the Economics of Biophilia Report from Terrapin, one of the leaders in this field of research.

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Figure 1 - Average physiological and psychological outcomes in baseline, after stressor and during the recovery period among four environments. (Effects of biophilic indoor environment on stress and anxiety recovery: between subject experiment in virtual reality, Jie Yin & co)

For instance, the results of this literature review suggest that there is a direct link within cognitive functioning and biophilic measures, where for cognitive function is intended our mental agility and attentiveness, as well as our ability to think, learn either logically or in a creative way.

Additionally, there is compelling evidence that strong or repetitive connections with nature can provide optimal opportunities for mental restoration. As a result, the capacity for performing focused tasks is enhanced when compared to someone not exposed to these connections with nature.

These effects are particularly relevant in schools. For instance, IAQ (Indoor Air Quality) in schools is much worse than outdoor air quality, in fact, indoor air pollutants may be 2-5 times higher than the outdoor environment.

Additionally, other reasons to consider IAQ in schools are that children breathe higher volumes of air, relative to their body weights, and they are particularly vulnerable to air pollution due to their narrower airways and the fact that their lungs are still developing.

Indoor climate control through biological processes

The biophilic patterns, as introduced in the previous blog post, can be designed and coupled with HVAC systems for several purposes, such as lowering the temperature of indoor spaces, removing VOC particles, improving air cooling, and cleaning indoor and outdoor water. However, what are exactly the biological processes involved?

One of them is called phytoremediation, and it is responsible for the removal of pollutants from the air, water, and soil.

It reduces the concentration and the toxic effects of contaminants in the environment by means of plants and soil microbes (fig 2). Moreover, it is accepted as a cost-effective environmental restoration technology, besides being a sound alternative to other methods, which are generally more destructive to the soil.

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Figure 2 - From left to right, schematic of the phytoremediation process and schematic of the biofiltration process. (Fig 1: source - Fig 2: source).

Another example of a biological process, which exploits plant characteristics, is biofiltration. This acts as a pollution control process, which utilizes microorganisms on a porous filter substrate. This basically involves the movement of harmful waste (odors air, contaminated water, etc.) through the medium, which works as a natural filter; this filter, in order to be effective, requires a large surface area, and it has to be a moisture retention surface with high porosity and structural integrity (fig.2).

Generally, the full capacity of plants as ‘air cleaners’ or ’green lungs’ of a building is highly affected by the set of boundary conditions in which they are located. It appears that the impact of vegetation in indoor spaces can be optimised when plats are combined with mechanical systems such as heating, ventilation, and air conditioning that are present in the space.

Biophilic HVAC systems

An example of biofiltration processes is an active green wall.

Active green walls differ from traditional ‘passive’ walls systems, as they serve more purpose due to the use of technology and smart sensoring. New technologies are in the direction of the integration of biofilters with air conditioning and ventilation systems.

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Figure 3 - From left to right, schematic of an active green wall and picture of an active green wall in a common space (Fig 3: source).

In an Active green wall, the air is forced to pass through the vegetated wall (the filter) to take advantage of their evaporative cooling potential as well as the capacity of these biofilters to purify the air. The main effects that are derived are that air is cooled, bio-filtered, and humidified thus potentially reducing ventilation requirements and the need for the standard filters used in air terminals.

As opposed to common green walls, these systems allow the movement of polluted air through the plant root systems and growing media and rely on a combination of plant leaves to adsorb or absorb pollutants from indoor air and biodegrade them in situ (Soreanu et al. 2013). The roots are, in fact, the parts of the plant system that have a ‘cleansing effect’ onto the air flowing by.

This type of green walls can also be smartly engineered to regulate peak performance with regards to indoor air quality and can be optimized according to the presence of people in the space.

Biophilic shading solutions

Thermal comfort within the buildings can be tackled by enhancing self-shading system, to reduce direct solar rays from reaching interior spaces and thereby mitigate cooling loads during summer periods.

With this purpose, biophilic patterns, such as Nature in the space and Nature of the space strategies (as presented in the previous blog) can be implemented within the building skin as integrated facades systems.

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Figure 4 - vegetative façade as Nature in the space pattern (Fig 4: source)

This is possible through the design of external vegetative shading systems that make use of deciduous plants. These are plants, including trees, shrubs, and herbaceous perennials, that lose their leaves for part of the year, usually in autumn. When applied as part of the façade shading system, this results in a consistent active shading throughout the spring and summer seasons, whereas for the autumn & winter seasons they allow solar gains, which is preferable.

Biophilic water treatment

Nature in the space patterns can be combined with solutions for rainwater collection and wastewater treatment in buildings.

By following the principles of phytoremediation there are a couple of examples that I would like to mention here.

A helophyte filter, which consists of a sand filter that is filled with vertical reeds and plants. The treatment of the rainwater is conducted by the bacteria present at the roots of the plants. The use of reeds is due to the necessary aeration of the roots and to capture nitrates and phosphorous.

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Figure 5 - Example of Helophyte filters (Fig 5: source)

With regard to wastewater from building use, this is most of the time considered a useless accepted waste, although there are technologies that can be applied to optimize its use, also in indoor environments.

Emerging technology is the Living Machine, which has been developed by John Todd Ecological Design. This machine is able to cleanse wastewater by mimicking the principles of the natural purification process of water bodies and wetlands. The system relies on a series of basins, which reproduce a specific ecosystem. These are then connected through pipes and contain living organisms from bacteria to trees, which feed on pathogens and pollutants and remove any unpleasant odors.

It is possible to customize the wastewater system by selecting the components of the treatment basins in accordance with the specific goals of the project.

The living machines are generally compact and can be adapted to diverse climates. However, rigid climates are not preferable and in fact, in these cases, they result to be more efficient in a greenhouse environment.

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Figure 6 - Example of a living machine for wastewater treatment (Fig 1: source - Fig 2: source)

Bridge the gap

Biophilia can help designers bridging the gap between an exclusively energy-focused approach and human-centered design, which provides invaluable benefits to the mood, health, and wellbeing of occupants.

The potential of biophilic patterns within our work of engineers and designers is terrific, especially when considering the combination of biophilia with mechanical systems for heating, cooling ventilation, and water re-use to control indoor environment for comfort.

From an engineering point of view, the mentioned integration of biophilic HVAC systems, shading systems, and water treatment offer practical examples of biophilic measures that have a significant climate control impact on the environments and that we can use to optimize resources.

At ABT we have the knowledge and experience to explore new creative solutions for the integration of biophilic patterns into the building space and envelope design, to maximize human comfort while simultaneously reduce the installations provisions as much as possible.


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