The energy required for the heating of a country’s building stock is a considerable part of its energy consumption. Insulation is one way to minimise energy loss, yet the insulation market has its own problems: lack of recycling, decreasing waste space and increasing demand. New insulation materials that are sustainable, biodegradable and highly performant are needed to combat this problem. Cellulose aerogel is a promising candidate with key properties we tested and measured. Yet this material is hydrophilic and combustible, and the methods used to counteract these problems are mostly chemical and not sustainable in nature. In order to bio-functionalise this material, we engineered a two layer protein coating that binds to the aerogel. The first layer protects the aerogel from water thanks to a silk biofilm. In particular, we characterised the green lacewing recombinant silk protein and demonstrated its hydrophobicity. The second layer consists of customisable proteins to further functionalise the material in any desired way, such as fire resistance. Hence we designed a whole new construct combining green lacewing recombinant silk protein with an existing fire-retardancy part (BBa_K1608000 from Mingdao 2015 iGEM team), the result is now available in the iGEM repository. We characterised the resulting biosynthetic material through material science protocols, reflecting the interdisciplinary intersection of our project and we proposed a proof-of-concept for the creation of a new insulation material. Further, we envisioned its sustainable and realistic implementation in the world by engaging with various actors of our society and communicated about the potential of synthetic biology in the construction field.

Figure 1An Overview of the HESTIA project

Heating is the new polluting luxury

The Background

More than 60% of all consumed household energy in Europe is dedicated to space heating.

The heating, or any temperature regulation, of our homes and workspaces constitutes a major section of our energy consumption and CO2 emissions. In Europe, space heating accounts for 62.8% of all household energy consumption1, and in 2017, in Switzerland, the energy consumption related to heating is 75% of all energy consumption from the Swiss building stock, with a staggering 75 TWh.

75% of the energy used for the heating of the building stock is acquired through fossil fuels, 50% from petroleum, and 25% from natural gas2. This means that ¾ of the energy used to heat all of the buildings in Switzerland is obtained from unsustainable and environmentally harmful sources, whose supply has been itself put under uncertainty in the recent months. Not only that, but the building stock in Switzerland constitutes 33% of all CO2 emissions of the country3.

The crippling of conventional sources of energy due to geopolitical reasons puts ¾ of the energy required by the Swiss building stock at risk. While other providers exist, it takes years to establish the infrastructure needed to transport the petroleum and the natural gas required. As such, blackouts are expected in Switzerland, and energy consumption reduction measures are being announced3.

The consumption of energy of the Swiss building stock, especially for heating, has to decrease drastically and the sources it relies upon need to be changed. Already, the Swiss Federal Office of Energy is pushing for the use of renewable energy sources in heating systems in its Building Stock Vision for 20504. In fact, the percentage of fossil fuels in the energy supply for the building stock fell to 58%5. Even so, the best energy is always energy not consumed.

Energy efficiency is a key pillar in any energy strategy and energy sobriety effort. Insulation lies in the centre of energy efficiency, as it reduces the amount of energy necessary to maintain a stable temperature inside. According to the Buildings Performance Institute Europe, an improved insulation can reduce the energy demand of a building by 45%6.

Yet, the current insulation materials in use are plagued by their own problems.

The Problem

Insulation waste is going to be 4 times worst by 2055.

The Swiss insulation market overall produces 275,900 tons every year. Only 1,800 tons of material ends up being recycled. 31,500 tons are incinerated, and 27,300 tons end up in landfills7. Unfortunately this problem is projected to get 4 times worse by 2055.

The amount of insulation waste increases, yet where is this waste stored? The landfills that house the insulation waste and all other types of waste material account for 40% of the 38,000 polluted sites in Switzerland (50% being industrial installations for comparison), all covering an area of 225 km28. These sites are considered as dangerous to public health and to the environment.

The second phase of the waste storage problem is that their capacity is about to be exceeded. In the Canton of Vaud, the amount of space to store construction waste is rapidly decreasing. The current capacity is already below the cantonal needs, and is projected to decrease further each year. From 2024 onwards (in two years), the existing construction waste storage space and the installations being planned combined will not be enough to satisfy the cantonal demand9. This leads to waste exports increasing, transferring the problem to other countries.

Reducing the production of insulation materials is not necessarily possible either. Due to strict construction and zoning regulations, not many new buildings are being built. Many people live in old buildings. The renovation of the building stock is therefore a more prominent issue in Switzerland in comparison with other countries, and an important part of renovating old buildings is to install new insulation or renew the existing one.

With minuscule recycling rates, decreasing waste space and production demand going up, a sustainable, recyclable, biodegradable and performant insulation material is needed.

Why a project in the construction sector ?

EPFL is an internationally well-known engineering school with a strong community of students with different scientific backgrounds, possessing both civil engineering and architecture sections. On the other hand, iGEM promotes multidisciplinarity in science through their judging criteria, even though it is certainly first a synthetic biology competition. In this regard, the EPFL iGEM 2022 team was composed to bring EPFL students' technical expertise in the iGEM competition.

Students studying life sciences engineering at EPFL are not the only ones to take part in the iGEM competition this year. Indeed, our team includes microengineering, mechanical engineering and architecture students. To take advantage of each student's particular competence depending on their scientific background, we looked for an interdisciplinary project’s subject.

As it is the first time that an architecture student is part of the EPFL iGEM team this year, we wanted to highlight this uniqueness. Thus, we came into the problems the construction field is facing and were deeply interested in taking part in the innovation in this field.


HESTIA signification

From Greek mythology, Hestia is the goddess of the hearth, or the home. Just like Hestia, our project aims to make each home a bit warmer, and safer. In our case, HESTIA stands for : Hydrophobic E.coli-based Sustainable Thermally Insulative Aerogel. By engineering a novel modular insulation material and opening the world of construction to synthetic biology, we hope to show the possibilities behind the combination of architecture, civil engineering and bioengineering.

New sustainable material

First discovered in 1931, aerogels are solid foam composed of a network of interconnected nanostructures that exhibit a porosity (non-solid volume) of no less than 50%. In addition, they can be harnessed in many applications and it widens their potential impact in technological innovations. Given the present environmental context, bio-based aerogels are drawing the attention of the materials scientists.

Cellulose aerogel is one of the most promising materials in the 21st century10. It is one of the most studied bio-based aerogel because of its diverse and interesting characteristics. Using cellulose as a precursor, which is the most abundant biopolymer on the planet, reduces the costs of fabrication in comparison to other scarce chemical precursors. In particular, cellulose aerogels have the renewability, biocompatibility, and biodegradability of cellulose, while also having additional advantages such as low density, high porosity, and a large specific surface area. All these features made us realise its potential as a sustainable thermal insulator in the construction sector.

HESTIA’s use of cellulose aerogel

Cellulose aerogels share the lower thermal conductivity (measured with the λ-value) of the aerogel family thanks to the Knudsen Effect. The size of the pores in an aerogel is smaller than the average free length of the path of gas molecules, causing the air molecules to collapse only with the pore wall without transferring energy. This lowers the overall thermal conductivity of the material.

In addition to that though, cellulose aerogels are more sustainable than other aerogel forming compounds. Cellulose is the most abundant biopolymer on Earth11. Wood fibres consist of 40%-60% cellulose12, and in cotton this rises to 90%13. In addition, cellulose can be produced by unicellular organisms. It is also easily recyclable and many systems exist to produce recycled paper, and more interestingly, cellulose sheets for insulation9. As an organic material, cellulose is highly biodegradable, decomposing in soil within weeks or months14. All of this makes cellulose a polymer able to satisfy the supply requirements and the sustainability concerns in an efficient and easy way.

The cellulose aerogel production method we chose was rather simple compared to the more developed and performant methods10. The more developed methods require expertise in material science, while a more simple approach results in a lower performance yet with a similar texture, adequate for a proof-of-concept approach.

Bringing synthetic biology to the construction industry

Tackling the Hydrophobicity Problem

Humidity is one way insulation materials are being damaged. While the cellulose aerogel is insulative, it barely has any protections against its surroundings. Cellulose aerogels are really water sensitive, as water damage makes their 3D structure collapse. This structure is vital for the thermally insulative properties. Therefore, it was necessary to provide waterproof protection to the material to increase its lifetime.

Chemical processes to make aerogels hydrophobic already exist and are even used in the industry. However, they all result in non-biodegradable products and follow non-sustainable or even toxic production methods. HESTIA’s vision is to develop a novel biodegradable insulative material and implement synthetic biology into the construction field. For this, working with hydrophobic proteins and leveraging them in a specific morphology suitable for the aerogel seemed like an optimal direction for the project.

When researching, silk proteins appeared like an easy implementable, accessible and sustainable option. Silk proteins demonstrate interesting mechanical properties such as toughness, strength, lightweight, biodegradability. As they aligned with HESTIA’s goals for the project, producing a hydrophobic biofilm made of a recombinant green lacewing silk protein became a core part of the Design.

Modular coating for different applications

During HESTIA’s brainstorming phase of the project, it seemed necessary to provide more features to the cellulose aerogel to obtain a more efficient and long-lasting insulation material. While waterproof protection appears essential, an insulation material can face other threats such as fire damage or mold caused by fungus. In order to prevent the aforementioned possible casualties, HESTIA sought to develop a coating made of proteins with the necessary properties to protect the material.

To build upon the spirit of iGEM, HESTIA wanted to build upon the work of previous iGEM teams and therefore explored the iGEM Registry looking for proteins with fire retardancy or fungus resistance. The Mingdao 2015 iGEM team documented the SRSF1 protein, which shows fire retardancy when phosphorylated. Therefore, it appeared to be the best candidate for testing the modular protein coating. Besides, we modeled how we could adapt the coating to infrastructures’ particular needs with ratios of proteins providing advantageous features.

To discover more about why we chose the green lacewing silk or more details about the recombinant protein itself, check out the Design Page.

Our engagement with the world

A project that doesn’t leave the laboratory is a dead project. To contextualise the HESTIA project and understand what sort of space it will occupy in the world, we got out of the walls of EPFL and interacted with many different actors to understand their concerns and to present our vision.

Human Practices

Our Human Practices work aimed to interact with as many involved actors in the production phase as possible, from raw materials to the end-users and regulators. We got in touch with insulation producers, architects, researchers, homeowners, regular citizens and much more. You can discover the fruits of this effort in the Human Practices page.

Education and Communication

The Education and Communication efforts centred on coming up with specialised methods in accordance with our target audiences. We engaged high school students with a summer school, the Swiss Youth with a Model United Nations focus group, our fellow iGEMers and more. We tried to raise awareness on the potential of Synthetic Biology but also on the importance of energy efficiency. You can check out the Education & Communication page to see how we spread the word.

Sustainable Development impact

To push for a meaningful Sustainable Development Impact and integrate the SDGs 9, 11 and 12; we stopped and thought about sustainability in each step. We consulted SDG stakeholders such as sustainability experts and SDG accelerators, and were inspired by their suggestions. This led us to make additions to our design that address both current challenges and a sustainable future. You can see how these considerations affected our project as a whole, you can check out the Sustainable Development Impact page.


A product is an Entrepreneurial entity as well. To understand how HESTIA would have its place in the current market, we conducted a market analysis and developed strategies to enter the market as smoothly as possible. In this, we took the specifics of our own material and the current realities in Switzerland and the insulation market. To see how we developed a realistic and data-based analysis, you can see the Entrepreneurship page.

Outlooks and future perspectives

HESTIA aims to produce an innovative insulation material from cellulose aerogel covered by a silk protein biofilm and a protein coating to open the construction world to synthetic biology. It aspires to make this novel material customisable to meet specific needs. One could focus on the modular protein coating. Proteins’ ratios could be tested with other proteins bringing useful features to the material. In this manner, one could control to which extent the material has what feature.

Additionally, two core values of HESTIA are biodegradability and sustainability. Some types of studies such as Life Cycle Assessment (LCA) have been conceived to compute precisely the environmental impact of a product. Such studies can bring an important added value to the project since it shows rigorously if your innovation is more sustainable than the current ones. Moreover, we could assess how the coated cellulose aerogel degrades over time to better understand which factor influences its lifetime. Hence, particular proteins affecting the sensitivity of the material to these factors could be identified and integrated to the modular protein coating.

HESTIA’s protein innovation on insulation material composed of a hydrophobic silk biofilm and a modular coating on top is only now applied to cellulose aerogels. This specificity is due to the cellulose-binding domain fused to the recombinant silk proteins. However, if some other protein domains specific to other materials can be fused to the silk protein and expressed, the whole proteins’ innovation could be applied to existing insulation materials.


  1. Eurostat-Statistics Explained (2022)
    Energy consumption in households
  2. Swiss Federal Office of Statistics (2017)
    Comment la Suisse se chauffe-t-elle? Les systèmes de chauffage d'aujourd'hui et de demain
  3. Erneuerbarheizen (2022)
    Rénovation et remplacement des systèmes de chauffage.
  4. Office Fédérale de L'Energie (2022)
    Parc immobilier 2050 – Vision de l’OFEN
  5. Office Fédérale de la Statistique (2021)
    Statistique des bâtiments et des logements 2021
  6. BPIE (2022)
    Putting a stop to energy waste
  7. Wiprächtiger, Haupt, Heeren, Waser & Hellweg (2020)
    A framework for sustainable and circular system design: Development and application on thermal insulation materials
    Resources, Conservation and Recycling, vol. 154, pp. 104631
  8. SuissInfo (2021)
    Cleaning up Switzerland’s toxic legacy
  9. Trois sœurs face aux seigneurs du béton (2021)
    Un ranch pour Avni Orllati
  10. Long, Weng & Wang (2018)
    Cellulose Aerogels: Synthesis, Applications, and Prospects
    Polymers, vol. 10, no. 6, pp. 623
  11. Klemm, Heublein, Fink & Bohn (2005)
    Cellulose: Fascinating Biopolymer and Sustainable Raw Material
    Angewandte Chemie International Edition, vol. 44, no. 22, pp. 3358-3393
  12. Zhu & Zhuang (2012)
    Conceptual net energy output for biofuel production from lignocellulosic biomass through biorefining
    Progress in Energy and Combustion Science, vol. 38, no. 4, pp. 583-598
  13. Hsieh (2007)
    Chemical structure and properties of cotton
    Cotton, pp. 3-34
  14. Chmolowska, Hamda & Laskowski (2016)
    Cellulose decomposed faster in fallow soil than in meadow soil due to a shorter lag time
    Journal of Soils and Sediments, vol. 17, no. 2, pp. 299-305