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- Project activities
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Last edited 03 May 2019
Aerogel insulation for buildings
Aerogels are synthetic low-density materials with unique physical properties. They
- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 03 May 2019
Aerogel insulation for buildings
Aerogels are synthetic low-density materials with unique physical properties. They are formed by removing the liquid from a gel under special drying conditions, bypassing the shrinkage and cracking experienced during ambient evaporation. This creates a solid three-dimensional nanoporous structure containing 80-99% air.
Due to their high porosity, aerogels exhibit the lowest thermal conductivity of any solid, whilst being transparent to light and solar radiation. Aerogels are often cited as a promising material for translucent insulation applications. They can made from practically any material, although the most common form is silica aerogel which can be produced as granules or in solid (monolithic) tiles.
- Cavity insulation.
- Glazing units and cladding systems containing granular aerogel.
- Translucent and opaque insulation boards, blankets and tensile roof membranes embedded with aerogel particles.
Transparent monolithic silica aerogel has been cited as the ‘holy grail’ of future glazing technology, with the potential to achieve U-values as low as 0.1 W/m2.K. However, research and development into monolithic glazing is limited due to the high cost of production, long processing time and the difficulty of creating large uniform samples with complete transparency.
The total thermal conductivity of porous insulation depends on the heat transfer through convection in the pores, conduction through the solid and pores, and radiation. Typically, pores within conventional insulation are over 1mm wide, allowing gas molecules to move freely and transfer thermal energy by convection. By comparison, pores within aerogel can be as small as 20-40nm (even smaller than the ‘mean free path’ of air at 60-100nm). As a result, individual air molecules within the pores have no space to transfer thermal energy by convection.
Conduction through the solid structure and air molecules within aerogel is also minimal. With little space for convection, air molecules constantly collide with the walls of the pores, suppressing gas conduction. Furthermore, as aerogel only contains 0.1-5% silica and the thermal conductivity of air is very low, heat transfer is minimal and conduction in the gas will diminish with any decreases in pressure. A vacuum inside the pores results in the best insulating properties, with thermal conductivity of 0.004 W/m.K (ten times better than conventional insulation).
The amount of radiative heat tra