Nano Aerogel: A Revolutionary Material Solving the Dilemma Between Thermal Insulation and Fire Protection in Building Facades

Thanks to its unique three-dimensional interconnected nanoskeleton and mesoporous network structure, aerogel has become the most known solid material with outstanding insulation performance to date. Its thermal conductivity at room temperature can be as low as 0.012 W/(m·K), only one-third to one-fifth that of traditional insulation materials, and even lower than static air. Against the backdrop of rising global building energy consumption and the accelerated advancement of the "dual carbon" goals, nanoaerogels, as a new generation of high-efficiency insulation materials, are gradually breaking the industry deadlock where traditional insulation materials cannot have both insulation performance and fire safety. This paper systematically reviews the development history and heat transfer mechanisms of aerogel materials, deeply analyzes the four mainstream application forms in the building exterior wall field (insulation coatings, thermal mortar, foam concrete, composite insulation boards) and the latest engineering practices, objectively assesses the core bottlenecks currently facing industrialization, and, combined with the latest technological breakthroughs in 2024, points out future development directions. Research shows that exterior wall insulation systems using aerogel can reduce heat loss by about 40%, and some actual engineering cases have seen comprehensive energy efficiency improvements of over 50%, making it a promising next trillion-yuan market in the field of building energy conservation.

1. Introduction: The Era Proposition and Industry Pain Points of Building Energy Conservation

1.1 Urgent Demand for Carbon Reduction in the Building Sector

The construction industry is one of the main sources of global energy consumption and carbon emissions. According to the "Research Report on Carbon Emissions in China's Urban and Rural Construction Sector" released by the China Building Energy Conservation Association in February 2025, in 2024, the nationwide energy consumption of civil buildings will reach 1.3 billion tons of standard coal, accounting for 21.8% of the country's total energy consumption; Operating carbon emissions reached 2.47 billion tons of CO₂, accounting for 22.1% of the country's energy carbon emissions. If carbon emissions from the production and construction stages of building materials are included, carbon emissions over the entire lifecycle of buildings now account for over 40%, making them a key battleground for achieving the "dual carbon" goals.

To address climate change, China has continuously raised building energy efficiency standards, gradually increasing from the initial 30% to 75% (GB 55015-2021), with provinces and cities like Beijing and Shandong taking the lead in raising standards to 80% and 83%, respectively. In March 2024, the General Office of the State Council forwarded the "Work Plan for Accelerating Energy Conservation and Carbon Reduction in the Building Sector," clearly stating that by 2025, the area of newly built ultra-low energy and near-zero energy buildings will increase by more than 20 million square meters compared to 2023, and by 2027, large-scale development of ultra-low energy buildings will be achieved. According to the Chinese government website, This policy direction places unprecedented demands on the performance of building insulation materials.

1.2 Technical bottlenecks of traditional insulation materials

However, traditional insulation materials can no longer meet increasingly stringent dual requirements for energy saving and safety, and the industry has long faced the dilemma of "insulation and fire prevention cannot be achieved simultaneously":

Organic insulation materials (such as polystyrene board EPS, extruded board XPS, polyurethane PU): have a low thermal conductivity (0.035-0.040 W/(m·K)), but are flammable and release large amounts of toxic smoke when burned, causing multiple high-rise building fire incidents. Even with added flame retardants, it is difficult to meet Class A fire resistance standards, and long-term use tends to age and peel off. Inorganic insulation materials (such as rock wool, glass wool, expanded perlite): Although they meet Class A fire resistance standards, their thermal conductivity is relatively high (0.040-0.070 W/(m·K)). To meet the energy-saving requirement of over 75%, the thickness of the insulation layer must be significantly increased, which not only raises the building load and construction difficulty, but also reduces indoor usable space, and poses issues such as water absorption and settlement.

Against this backdrop, nanoaerogel, praised by Science magazine as one of the "Top Ten Amazing Materials That Can Change the World," has become an effective solution to the pain points of the exterior wall insulation industry thanks to its ultra-low thermal conductivity, Class A fire resistance, ultra-long service life, and lightweight design. In October 2021, the State Council issued the "Opinions on Fully, Accurately, and Comprehensively Implementing the New Development Philosophy and Doing a Good Job in Carbon Peaking and Carbon Neutrality," clearly proposing to "research and promote aerogel and other new insulation materials," laying a solid policy foundation for the large-scale application of aerogel in the construction sector.

2. Characteristics of nano aerogels and ultra-low heat transfer mechanisms

2.1 Basic Properties of Aerogel

Aerogel is a three-dimensional porous solid material formed by interconnected nano-sized particles, with a porosity as high as 90%-99.8%. Among them, silicon dioxide (SiO₂) aerogel is currently the most mature and widely used variety. Its core features can be summarized as lightweight, highly efficient thermal insulation, high fire resistance, and long lifespan:

Lightweight: Density can be as low as 0.003 kg/m³, making it an extremely low-density solid material, vividly known as "solidified smoke" or "blue smoke." Highly efficient insulation: At room temperature, thermal conductivity can be as low as 0.012 W/(m·K), lower than stationary air (0.025 W/(m·K)), which is 1/3 to 1/5 of traditional insulation materials. High fire resistance: Inorganic aerogel is non-flammable, with combustion performance meeting national standard A1 level, no toxic gases released at high temperatures, long lifespan: chemically stable and strong weather resistance. The service life can reach over 50 years, matching the lifespan of the main building structure

2.2 Ultra-low heat transfer mechanism of aerogels

The reason aerogels can achieve superior thermal insulation performance over traditional materials lies in their unique nanostructure, which comprehensively and efficiently suppresses the three basic heat transfer methods, which is also a key difference from traditional porous materials:

Nanoscale inhibition of solid heat transfer

The solid framework of aerogel consists of silica nanoparticles with diameters of 20-50 nm. Due to the "size effect," phonons (carriers for solid heat conduction) are strongly scattered at the interface of nanoparticles, significantly shortening the mean free path and significantly reducing the efficiency of solid heat conduction. The solid thermal conductivity of pure silica aerogel is only 0.005-0.025 W/(m·K), which is lower than traditional inorganic materials.

Inhibition of the Knudson effect in gas heat transfer

The pore size of aerogel is mainly distributed in the range of 20-50 nm, which is smaller than the average free path of air molecules (about 70 nm, at 25°C atmospheric pressure). According to the Knudson effect, when the pore size is smaller than the mean free path of gas molecules, the collision frequency between gas molecules drops significantly, effectively suppressing gas heat conduction. At the same time, due to the extremely small pore size, air convection cannot be formed, so convective heat transfer can be basically neglected. This is equivalent to putting a "brake" on the air at the molecular level, preventing heat from transferring.

Multiple thermal barrier effects of radiative heat transfer are suppressed

The three-dimensional mesh structure of aerogel forms countless tiny thermal barriers that can repeatedly reflect and scatter infrared radiation, producing a "multiple thermal barrier effect." Although radiant heat transfer is enhanced in high-temperature environments (>300°C), adding a small amount of infrared light-blocking agents (such as carbon black, titanium dioxide, silicon carbide) can further reduce the thermal conductivity at high temperatures by more than 50%.

It is worth noting that recent studies show that the effective thermal conductivity of aerogel includes not only solid, gas, and radiation but also the gas-solid coupled heat transfer effect. This effect accounts for about 10%-15% of the total thermal conductivity, and its findings provide a new theoretical direction for further optimizing the thermal insulation performance of aerogels.

3. Progress and Engineering Practice of Aerogel Application in Building Exterior Wall Insulation

In recent years, researchers at home and abroad have developed various forms of aerogel building insulation products, covering four major categories: coatings, mortar, foam concrete, and composite insulation panels. Some of these products have been successfully applied in national-level key projects such as the Beijing Winter Olympics and Xiong'an New Area.

3.1 Aerogel Insulation Coatings: The ideal choice for existing building renovations

Aerogel insulation coating is a functional coating made by mixing silica aerogel microspheres with resin and additives. It offers advantages such as easy application, strong adhesion, does not alter the building's appearance, and can be applied to complex curved surfaces, making it especially suitable for energy-saving retrofits of existing buildings.

In 2019, a domestic research team successfully produced a high-performance insulation coating by combining silica aerogel microspheres with acrylic emulsion. Research has found that when the aerogel volume fraction exceeds 30%, the thermal conductivity of the coating significantly decreases as the aerogel content increases. In 2022, after further formulation optimization, aerogel coatings with thermal conductivity as low as 0.050 W/(m·K) and bonding strength reached 1024 kPa, fully meeting the mechanical performance requirements for exterior wall coatings.

3.2 Aerogel Insulation Mortar: Compatible with traditional construction techniques

Aerogel insulation mortar is a ready-mixed mortar made by mixing granular silica aerogel into cement-based cementitious materials. It can be directly applied to wall surfaces, and the construction process is fully compatible with traditional cement mortar, without the need to alter existing construction workflows.

Research shows that when the aerogel volume fraction reaches 60%, the thermal conductivity of mortar drops from 0.6039 W/(m·K) to 0.1524 W/(m·K), while maintaining a flexural strength of 0.45 MPa and a compressive strength of 2.15 MPa. In a practical project in Germany, commercial aerogel mortar was used to reduce the heat transfer coefficient of exterior walls built in 1989 from 1.0 W/(m²·K) to 0.3 W/(m²·K), effectively eliminating the thermal bridging effect in wall gaps and achieving significant energy savings.

3.3 Aerogel Foam Concrete: Integrated Structure and Insulation

Aerogel foam concrete is a lightweight insulation material made by introducing aerogel particles into foamed concrete. It combines both insulation and structural functions, and can be directly used for pouring building walls, achieving integrated structural and thermal insulation and significantly shortening the construction period.

In 2019, domestic researchers optimized the ratio of cement, aerogel, and foam to produce high-performance aerogel foam concrete with a density as low as 198 kg/m³ and a thermal conductivity as low as 0.049 W/(m·K). Comparative experiments show that compared to ordinary concrete, aerogel concrete can reduce heat loss by about 33%. In 2023, by adopting a new ultra-lightweight aerogel technology (75 kg/m³), aerogel usage was reduced by 49% while maintaining the same insulation performance, significantly lowering material costs.

3.4 Aerogel composite insulation board: a product with a high degree of industrialization

Aerogel composite insulation boards are currently one of the most thoroughly researched and industrialized aerogel building insulation products. They are usually made by combining aerogel particles with fiber-reinforced materials, featuring low thermal conductivity, high strength, dimensional stability, and ease of installation, making them an ideal alternative to traditional insulation boards.

Events such as the Wukesong Ice Hockey Arena and the Winter Olympic Village Comprehensive Clinic at the Beijing Winter Olympics have adopted aerogel vacuum insulation panels, with a thermal conductivity less than or equal to 0.005 W/(m·K), insulation performance six times that of EPS boards and seven times that of rock wool boards, and fire resistance rating reaching Class A. In the exterior wall insulation project in the Xiong'an New Area resettlement area, using aerogel insulation felt reduced construction losses by 27% and shortened the construction period by 15%, directly saving nearly one million yuan in construction costs.

In April 2026, China National Chemical Engineering 16 Chemicals was the first to apply aerogel technology to large-scale cold storage insulation in the agricultural and sideline products e-commerce cold chain logistics base project in Gong'an County, Hubei. This aerogel insulation blanket has a thermal conductivity as low as 0.021 W/(m·K) and combustion performance up to Class A1, effectively solving the flammable safety hazards of traditional polyurethane insulation materials.



4. Core Challenges and Breakthroughs in Industrialization and Latest Technologies

Although aerogel shows enormous application potential in building exterior wall insulation, it still faces three core challenges that limit its large-scale adoption.

4.1 Research on heat transfer mechanisms needs further in-depth

Although the basic heat transfer mechanisms of aerogel have been extensively studied, our understanding of the nanoscale effects, interface effects, and gas-solid coupling effects in composite aerogel materials remains insufficient. Currently, there is a lack of unified thermal conduction calculation models and standardized testing methods, making it difficult for designers to accurately predict the actual energy-saving effect of aerogel insulation systems, nor to optimize designs.

4.2 Production costs remain high

High costs are the main factor limiting large-scale aerogel application. Traditional aerogel preparation processes use expensive silicone precursors (such as ethyl orthosilicate) and supercritical drying technology, resulting in high raw material costs, long production cycles, and high energy consumption, resulting in aerogel insulation materials costing 5 to 10 times more than traditional insulation materials.

4.3 The standard system is still imperfect

Currently, China has not yet issued national or industry standards specifically for aerogel insulation materials for buildings, resulting in inconsistent product quality and a lack of basis for project acceptance. Design units are unable to implement energy-saving designs according to existing standards and can only promote them through pilot projects and expert evaluations.

4.4 Latest Technological Breakthroughs in 2024

Encouragingly, in 2024, global aerogel technology achieved multiple major breakthroughs, bringing hope to solving cost issues:

Institute of Physical and Chemical Technology, Chinese Academy of Sciences: Developed flash synthesis technology for silicon carbide aerogel, utilizing the rapid combustion synthesis reaction between silicon powder and PTFE reactant, capable of producing 16 liters of aerogel per minute, increasing production speed tenfold and reducing manufacturing costs by two orders of magnitude, costing only 5 yuan per liter. Fraunhofer Institute in Germany: Developed an innovative aerogel production process that reduces production time from over ten hours to four hours, reduces manufacturing costs by 70%, and ensures that the production process contains no environmentally harmful chemicals. Zou Ruqiang's team at Peking University: proposed a new strategy to construct micron-scale porous aerogel frameworks using phase change materials, resulting in novel phase change aerogel materials with mild reaction conditions, low process costs, and promising prospects for large-scale application.

5. Future Development Directions and Outlook

To address these challenges, future research and industrialization of aerogel in building exterior wall insulation should focus on the following aspects:

Strengthen basic theoretical research: Conduct in-depth research on the quantitative relationship between the microstructure and macroscopic properties of aerogel, establish unified multi-scale heat conduction calculation models and standardized testing methods, and provide a solid theoretical foundation for the design and application of aerogel insulation systems.

Accelerate the industrialization of low-cost technologies: Vigorously promote atmospheric pressure drying technology using water glass as the silicon source and the latest flash synthesis technology, develop continuous, automated production lines, and strive to reduce the cost of aerogel insulation materials to less than twice that of traditional materials within 3-5 years, making them competitive in the market.

Optimizing composite formulations and structural design: By combining with traditional insulation materials, aerogel usage is reduced while ensuring insulation performance. For example, combining aerogel with rock wool or glass wool can simultaneously improve insulation and mechanical properties, reducing overall costs.

Improve the standard system and policy support: Accelerate the formulation of product standards, engineering technical specifications, and acceptance standards for aerogel insulation materials for buildings, and regulate market order. At the same time, it is recommended that the government introduce special subsidy policies to provide financial support for ultra-low energy consumption buildings using aerogel insulation materials, accelerating market promotion.

6.Conclusion

As a new generation of high-efficiency insulation material, nano-aerogels, with their ultra-low thermal conductivity, Class A fire resistance, long service life, and lightweight advantages, provide an innovative solution to the industry's pain point of "insulation and fire protection cannot be achieved simultaneously" in building exterior wall insulation. At present, significant research progress has been made on four main types of products: aerogel coatings, mortars, foam concrete, and composite insulation boards. They have been successfully applied in national key projects such as the Beijing Winter Olympics and the Xiong'an New Area, achieving remarkable energy-saving effects. Although the large-scale application of aerogels in the construction field still faces challenges such as insufficient research on the heat transfer mechanism, high production costs, and an imperfect standard system, the major breakthroughs in global aerogel technology in 2024 have brought hope for solving the cost issue. It is foreseeable that, with strong policy support and continuous technological advancement, nano-aerogels will gradually replace traditional insulation materials in the next 5-10 years, becoming the mainstream product in the building exterior wall insulation market and making an important contribution to achieving the "dual carbon" goal and the green and low-carbon transformation of the construction industry.