When discussing sustainability in construction, we are used to an approach based on complex technological solutions, expensive sensors, costly materials and, most recently, artificial intelligence. But what if everything we are looking for (in terms of sustainability) could come from the materials themselves, taking advantage of their intrinsic properties, without even relying on electricity? The use of hygromorphic materials offers an innovative perspective and sheds light on little-explored possibilities in the field. These materials can adapt to variations in environmental humidity, changing their shape, size or other physical properties. Examples in nature include wood, hygroscopic proteins such as collagen, polysaccharides such as cellulose and chitin, hygroscopic minerals such as certain salts and silica gel, as well as spores and pollen grains; all of which exhibit the ability to absorb or release moisture in response to changes in humidity. In architecture, researchers have been striving to develop materials, particularly for façades, that can take on a life of their own and make buildings more comfortable naturally.
Faced with the significant environmental impact caused by the construction industry, the search for ways to improve efficiency and reduce the impact of buildings is becoming a pressing need. In this scenario, façades have taken on a fundamental role as the front line of protection between the interior and exterior of buildings, emerging as a promising starting point for initiatives aimed at sustainability in construction. In an interview with Professor Ben Bridgens of Newcastle University, co-director of The Hub for Biotechnology in the Built Environment (HBBE), a pioneering initiative between Newcastle University and Northumbria University, we explored an innovative vision: developing biotechnologies to create a new generation of living buildings. The idea is to develop buildings that are not only responsive and adaptable to their natural environment, but that can also be grown using engineered living materials to reduce inefficient industrial construction processes. This approach points to a future where sustainable construction not only protects the environment, but also integrates harmoniously with it, promoting a regenerative and resilient life cycle for built structures.
According to Bridgens, his interest in hygromorphic façades was sparked when he read an article in Architectural Design entitled "Material capacity - embedded responsiveness" by Achim Menges and Steffen Reichart, which presents prototypes of wood in a two-layer construction that react to changes in humidity, enabling a façade to open and close in response to environmental variations. At the same time, Ben was becoming disenchanted with overly technological approaches to sustainable architecture. Hygromorphic materials therefore emerged as a remarkably elegant solution, allowing buildings to adapt and respond without relying on sensors, motors, processors and energy.
Hygromorphic materials have the potential to provide low-cost, low environmental impact, low maintenance responsive façades which reduce the energy use of buildings. But implementing them in a way that achieves this is actually very challenging—and this is what our research has been focused on.
The lab's researchers are currently involved in two primary hygromorphic projects. The first, RESPIRE (Passive, Responsive, Variable Porosity Building Skins), funded by the Leverhulme Trust, investigates the use of bio-based hygromorphic materials to create adaptable and breathable façades. The other project explores the use of bacterial spores as highly responsive hygromorphs. According to Ben, both must overcome certain similar challenges:
The first is to understand the environmental conditions in a comprehensive way: although hygromorphs react to humidity, the main objective of a responsive façade is to regulate the internal temperature, which doesn't always correlate directly. For example, in scenarios where south-facing façades (in the northern hemisphere) become excessively hot, the goal is to close the shading to mitigate solar gain. Through various analyses, it has been observed that in the UK there is a very limited correlation between relative humidity and temperature. In New Delhi, on the other hand, there is a strong correlation between the two in summer, which could represent a huge potential for use.
To create functional and responsive façades using hygromorphs, we must also be able to 'program' the materials to work under specific conditions. Ben points out that, "for example we might need a material which is curved at 40% relative humidity, and flat at 70% relative humidity. For both wood veneer and bacterial spore hygromorphs we've developed fabrication methods which enable us to specify this behavior by controlling the fabrication conditions."
Another critical limitation is the speed of response. That is, some materials have response times of minutes and others of months. "Bacterial spores have the fastest response times, and can respond in a few minutes, and wood-based hygromorphs can be designed with response times from minutes to hours to weeks depending on the thickness of the wood and the construction of the bilayer material." This makes it possible to develop building façades that respond to various stimuli, including short-term weather events, daily cycles and seasonal changes.
Finally, there is the durability factor. Any building material must last for years or even decades without maintenance or degradation of performance.
We’ve tested wood veneer hygromorphs externally for over 2 years and found very good durability; this was achieved after extensive testing of different material combinations, adhesives, and fabrication methods. And we can think about how the hygromorph is installed in the building—robust wood-based hygromorphs could be installed externally, but more fragile systems using very thin wood veneer or bacterial spores could be installed within a double skin façade so they are protected from wind and rain.
According to Ben, research into new materials and techniques plays a key role in pushing forward sustainability goals on a global scale. Research into hygromorphic materials has revealed promising opportunities for improving the efficiency of buildings and reducing energy consumption, particularly in regions with extreme climates such as New Delhi. By developing hygromorphic shading and ventilation systems adapted to the specific environmental conditions of such locations, dependence on energy-intensive air conditioning can be significantly reduced. "We've developed a hygromorphic screen made from woven wood veneer, which opens passively at night to provide night ventilation, and closes during the day. This could be retrofitted to existing buildings, and made using local wood and skills. This is the key to advancing global sustainability: using research to develop simple, local solutions tailored to specific climates, building typologies and cultures."
He adds: "Our work in the Hub for Biotechnology in the Built Environment at Newcastle and Northumbria Universities emphasizes a holistic approach towards creating 'living buildings' that are both life-sustaining and sustained by life." By using engineered living materials, such as hygromorphic materials, these buildings can mitigate the environmental impact of traditional industrial construction processes. In addition, they have the ability to metabolize their own waste, thus reducing pollution, generating energy and producing high-value products.
The incorporation of hygromorphic materials into adaptive architectural façades could be a significant milestone in the advancement of sustainable design practices, by drawing inspiration from natural behavior and applying it to construction. With further exploration and innovation, these materials have the potential to transform the world of construction, offering a path to a more sustainable future built on nature's own mechanisms. This means developing and extending biotechnologies to create a new generation of 'living buildings' that are responsible and responsive to their natural environment.
To keep up with HBBE publications, visit the official website.
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