Aerogel is the highest-performing thermal insulation material ever commercialized, delivering R-values of R-10 to R-14 per inch, roughly 2 to 3 times the performance of conventional foam board insulation. Invented in 1931 by Samuel Kistler at the College of the Pacific in Stockton, California, aerogel is produced by replacing the liquid component of a gel with gas while preserving the gel's solid nanostructure. The resulting material is composed of 97 to 99.8 percent air by volume, with a density as low as 0.003 grams per cubic centimetre, earning it the colloquial name "solid smoke" or "frozen smoke."
How Aerogel Works
Silica aerogel achieves its extraordinary insulating performance through its nanoporous structure. The pore size in aerogel is typically 2 to 50 nanometres, which is smaller than the mean free path of air molecules at atmospheric pressure. This means that air molecules within the aerogel matrix collide more frequently with the pore walls than with each other, dramatically suppressing both gaseous conduction and convection. Solid conduction through the silica skeleton is limited by the extremely low density and the tortuous path heat must follow. Radiative heat transfer becomes the dominant remaining mode, which is why commercial aerogel insulation products incorporate infrared opacifiers such as carbon black into the silica matrix.
Product Forms
Commercial building insulation products use aerogel in two primary forms. Aspen Aerogels, headquartered in Northborough, Massachusetts, produces Spaceloft, a fiber-reinforced aerogel blanket available in 5 mm and 10 mm thicknesses. The flexible blanket format allows aerogel to be cut and wrapped around pipes, ducts, and structural elements, making it the preferred solution for thermal bridge mitigation where thin, high-performance insulation must fit into constrained spaces. Spaceloft is installed against concrete slab edges, steel beams, window frames, and other assemblies where a few millimetres of conventional insulation would be insufficient but aerogel can deliver meaningful thermal resistance.
Cabot Corporation produces Nanogel, a granular form of aerogel used in translucent daylighting panels. When sandwiched between polycarbonate or glass panels, Nanogel-filled units transmit diffused daylight while providing high thermal insulation, enabling naturally lit building envelopes without the energy penalty typical of large glazing areas.
Space and Extreme Environment Applications
Aerogel's most visible application is in space exploration. NASA has used silica aerogel as insulation on Mars rovers including Sojourner, Spirit, Opportunity, and Perseverance, protecting sensitive electronics from the extreme temperature swings on the Martian surface, where daytime highs and nighttime lows can differ by 90 degrees Celsius or more. Aerogel was also used on the Stardust mission, which launched in 1999, as the capture medium for cometary dust particles. The ultra-low-density aerogel could decelerate particles travelling at 6 kilometres per second without destroying them, preserving them for laboratory analysis on Earth.
Building Applications and Cost
In building construction, aerogel addresses a specific problem: thermal bridging through structural elements. Where a steel beam or concrete slab penetrates the insulated building envelope, conventional insulation must be cut away, creating a conductive path for heat loss. Aerogel blankets as thin as 5 mm can wrap these elements and provide enough thermal break to prevent condensation, mold growth, and energy loss. Aerogel is also used in historic building retrofits where interior insulation must be as thin as possible to preserve room dimensions and architectural features.
The cost of aerogel insulation is its primary limitation. A 10 mm Spaceloft blanket costs approximately USD 20 to 50 per square foot, which is 10 to 20 times the cost of conventional insulation delivering equivalent total R-value. For this reason, aerogel is used strategically in small quantities at thermal bridges rather than as a full-envelope insulation solution. Its use in buildings is concentrated in high-performance projects, Passive House construction, and historic retrofit applications where the thin profile justifies the premium.
Hydrophobic and Hydrophilic Types
Most commercial aerogel insulation is hydrophobic, meaning it repels liquid water while allowing water vapour to pass through. This is achieved through surface chemistry treatment during manufacturing that replaces hydroxyl groups on the silica surface with non-polar groups. Hydrophobic aerogel can be exposed to rain during construction and will not lose its insulating performance. Hydrophilic aerogel, which absorbs water, is used primarily in non-building applications such as chemical catalysis and medical drug delivery. For building applications, hydrophobic aerogel is the standard specification.