Aerogels are groundbreaking materials in numerous industries. Their unique properties make them suitable for multiple innovative applications, and in recent years, the construction industry’s interest in these materials has accelerated. This article will explore the use of aerogels in buildings.
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What are Aerogels?
Aerogels were first developed in the 1930s, but it was not until the late 1980s/early 1990s that research into these materials accelerated with the introduction of carbon aerogels.
As low-density, solid-state materials, aerogels are produced by replacing the liquid component of a gel with gas, retaining its structure whilst significantly reducing its density. Another term for this innovative class of material is “liquid smoke” due to how light scatters through it and its semi-transparent appearance.
The gel’s liquid component is extracted by supercritical drying, wherein the liquid is drawn out of the gel in a supercritical state. In this state, the distinction between liquid and gas phases within the material no longer applies. Compared to conventional evaporation, supercritical drying does not cause the solid matrix to collapse.
Aerogels are extremely strong but prone to shattering. These materials possess remarkable properties such as high strength (they are able to support structures many times their weight,) lack of electrical conductivity, low dielectric constant, high specific surface area, and outstanding thermal and acoustic insulation.
These remarkable materials can be made from a variety of precursor materials, such as silica, carbon, organic polymers, iron oxide, copper, and gold. Once prepared, very little of the solid material remains, and the structure of the final material is composed of up to 99.8% air.
How Can Aerogels Be Applied in Buildings?
The favorable properties of aerogels make them suitable for innovative applications in a number of industries, including construction. As the sector seeks to fulfill its net zero obligations and economic challenges and embrace new technologies, research into aerogels for use in buildings has accelerated in recent years.
Aerogels possess outstanding thermal and acoustic insulation properties and fire retardation possibilities. They can be applied in soundproofing, fireproofing, and as insulation for enhancing the energy efficiency of buildings either in new structures or in retrofitting existing ones.
Research into using silica-based aerogels as insulating materials has provided some noteworthy results. Additionally, incorporating these innovative materials into structural composites and framing elements reduces the overall weight of buildings whilst providing enhanced thermal insulation.
Another innovative use for aerogels in buildings is in air purification. Indoor environments are full of pollutants, such as hydrocarbons from cigarettes, VOC from organic solvents, SOx and NOx from incomplete gas burning, and formalin from paints. These are all linked with poor health and the prevalence of respiratory conditions.
Due to its large specific surface area and higher porosity (which can be controlled during the manufacturing process), aerogel is better at removing these contaminants than activated carbon.
Studies have indicated that metal oxide semiconductors prepared using aerogels show efficient removal of a wide range of contaminants. Notably, this requires negligible energy input. Research has also demonstrated the favorable air purification capabilities of aerogel-prepared MgO, Al2O3 nanocrystals.
Aerogels have also been explored for super-insulating glazing applications. Some interesting research has produced glazing with granular silica aerogel sandwiched between polymer sheets to produce highly efficient thermal insulation products. This could significantly save costs for new builds and retrofits.
Aerogels have also been applied in solar energy as covers for solar collectors. Aerogel blankets can be used as advanced insulation with hydrophobic properties for a variety of building elements such as attics, walls, and groundsheets.
Economic Challenges
Aerogel-based building projects have already appeared on the market and whilst highly promising, the large-scale deployment of these technological solutions does face some key challenges.
Not least among these challenges is the economic viability of large-scale aerogel use in the construction sector. Thus far, cost considerations have largely limited their use in building materials and systems. Whilst well-established, the small scale of aerogel production techniques at present increases costs significantly.
The supercritical drying process, which forms the basis of aerogel production techniques, takes a long period of time, again leading to higher production costs than conventional insulating materials. For instance, an aerogel-based window is six times more expensive than conventional double glazing.
For aerogels to be considered viable large-scale construction materials, production costs have to fall. Ambient drying can be used to produce aerogels, which can reduce costs, lower energy requirements, and simplify the process, but large-scale implementation of this process is still some way off.
Conventional foam insulation is more cost-effective than aerogel blankets, but the cost of aerogel blankets is acceptable for industrial applications and some domestic ones. Some estimates have put the cost of one centimeter-thick aerogel blankets at between $20 - $35/m2.
Sustainability Compared to Other Materials
However, one area where aerogels are significantly more beneficial for building projects is their sustainability. They are user-friendly, non-toxic, recyclable, and reusable. Aerogels can also be produced from organic precursor materials such as chitosan, cellulose, or alginate, improving their green chemistry credentials.
Many conventional materials used in construction for the same purposes as aerogels are difficult to recycle or dispose of at the end of their lives, which is especially problematic as the industry seeks to improve its green credentials. Aerogels could significantly contribute to the future sustainability of the construction sector.
Final Thoughts
Aerogels could revolutionize the construction industry, providing new, highly efficient, cost-effective, and environmentally friendly materials for applications such as thermal insulation, energy-efficient devices, air purification, glazing, soundproofing, fire retardants, and some structural elements in new builds and heritage buildings.
Whilst the manufacturing process for aerogels is currently cost-prohibitive, scaling their production up to industrial levels will lead to unit cost reduction and mean that aerogels and aerogel-based systems will be able to compete with well-established, conventional building materials for a myriad of key building applications.
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References and Further Reading
Lamy-Mendes et al. (2021) Progress in silica aerogel-containing materials for buildings’ thermal insulation Construction and Building Materials 286, 122815 [online] sciencedirect.com. Available at:
https://www.sciencedirect.com/science/article/abs/pii/S0950061821005754
Ganobjak, M., Brunner, S. & Wernery, J (2020) Aerogel materials for heritage buildings: Materials, properties and case studies Journal of Cultural Heritage 42 pp. 81-98. Available at:
https://www.sciencedirect.com/science/article/pii/S1296207419302080
Riffat, S.B. & Qui, G (2012) A review of state-of-the-art aerogel applications in buildings International Journal of Low-Carbon Technologies 8:1 [online] academic.oup.com. Available at:
https://doi.org/10.1093/ijlct/cts00
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