In developed countries and many countries, greenhouse gas emissions are a big problem today. One of the most cost-effective actions to reduce greenhouse gases is to improve the heat insulation of residential and commercial buildings. Obviously, in order to have better insulation in buildings, traditional insulation can be used for thicker or multi-storey buildings.

Nevertheless, new materials with better thermal properties, such as aerogel and vacuum insulating panels, are being investigated for use in buildings. The goal of building sustainability can only be achieved through the production of new advanced materials and the use of these materials, especially on glass surfaces. Under different external forces, the durability of the building can be increased, and energy efficiency can be improved through high levels of insulation.

Aerogel is considered to be one of the most promising high-performance thermal insulation materials for building applications today. Compared with traditional thermal insulation materials, the thermal conductivity of aerogel is reduced to 0.013~0.018W/(m·K). The construction industry is also interested in the high transmittance in the solar spectrum. With the right knowledge, both architects and engineers have the opportunity to reinvent building solutions. In this work, we review the knowledge of aerogel insulation in general, and construction applications in particular. Aerogel is a synthetic porous hyperoptical material in which the liquid component of the gel is replaced by a gas. It is an advanced material that contains 15 records in the Guinness Book of World Records for properties such as the lowest density solid and best insulator. It is a silicon-based substance made up of a loose network of silicon atoms.

Aerogel is a nanoparticle invented in the 1930s - aerogel is formed when silica is glued in a solvent, and when the solvent is removed, what remains is "expanded sand" with a porosity of up to 99%.

The nano-ore seals the air molecules, and the heat flow and long molecular chains increase the length of the solid channel through the silica, reducing the thermal conductivity. These two innovations helped move aerogels from lab curiosities to industrial products. Supercritical carbon dioxide 2 extraction reduces cycle time from months to hours and provides mechanical integrity by casting the wet gel into a fiber strike.

1. Aerogel felt

Aerogel felt is a new type of material that has extremely low thermal conductivity, making the material a good insulating material. In fact, aerogel blankets are now being used to improve the energy performance of existing walls. Using aerogel blankets as insulation for walls means replacing existing insulation. When materials in building components are replaced to improve a particular performance, it is important to verify the impact of other functional requirements of the wall such as fire resistance.

Aerogel is a synthetic low density material with unique physical properties. They are formed by removing the liquid from the gel under special drying conditions, bypassing the shrinkage and cracks experienced during evaporation in the ring 墇. This creates a three-dimensional nanopore structure that contains 80-99% air. Due to its high porosity, aerogel has a lower thermal conductivity than any solid, while being transparent to light and solar radiation. Aerogel is often considered a promising material for translucent insulation applications. They can be made from almost any material, although the most common form is silica gel that can be produced as pellets or in round (monolithic) tiles. General commercial products in the construction industry include: stomatal insulation, polishing devices containing particulate gas, and cladding systems

Supercritical CO2 extraction reduces cycle time from months to hours and casts the wet gel into fibers, providing mechanical integrity. Translucent and opaque insulating panels, blankets and stretchable roof membranes are embedded with aerogel particles. Transparent monolithic silicone aerogels are considered the "Holy grail" of future glazing technology, with U-values that can be as low as 0.1W/M2.K. However, due to high production costs, long processing times, and the difficulty of producing a large uniform sample that is completely transparent, the research and development of the whole glass is limited.

2. Aerogel performance

The total thermal conductivity of porous insulating materials depends on the convective heat transfer in the holes, the conduction and radiation of solids and pores. In general, the pores in traditional insulating materials are more than 1 room meter wide, allowing the gas molecules to move freely and transfer heat energy through convection. In contrast, the pores in aerogel can be as small as 20-40 miles (even smaller than the "mean free path" at 60-100 miles). As a result, the individual air molecules inside the hole have no room to transfer heat energy through convection.

The conduction of air molecules through the solid structure and within the aerogel is also minimal. Due to the small convection space, air molecules constantly collide with the pore wall, inhibiting gas conduction. In addition, since the gas coagulant contains only 0.1.5% silicon dioxide, the thermal conductivity of the air is very low, the heat transfer is very small, and the electrical conductivity of the gas decreases with the reduction of pressure. The vacuum in the pores gives it the best insulation performance, with a thermal conductivity of 0.004W/MM.K(10 times higher than conventional insulation).

The radiative heat transfer of aerogel depends on the intensity and wavelength of the thermal radiation, the optical properties of the material, the size and shape of the pores, and their overall thickness. At ambient temperature

Due to high absorption and high reflection levels, nanopore and particle provide effective infrared thermal radiation attenuation. The optical and infrared properties of silica aerogel are studied. Silica aerogel can be considered as a transparent insulating material that effectively transmits solar energy, but can block thermal infrared radiation. The material presents a high semi-transparency, often accompanied by a slight blue mist. This can be attributed to "Rayleigh scattering," a light phenomenon that occurs when light scatters particles smaller than light wavelengths, with the shorter wavelengths of the blue spectrum most easily scattered.

3. Environmental impact

Preparation of aerogel involves three key steps: gel preparation, aging and drying. The aim is to build a gel, strengthen and purify it, and then remove all the liquid from the hole without collapsing the solid structure (achieved by supercritical or subcritical drying techniques). These processes often involve mixing quite toxic chemicals and undertaking complex diffusion control processes that consume large amounts of solvents. In addition, the last step is often accompanied by an intensive drying process that can consume large amounts of energy and carbon dioxide.

4. Advantages of aerogel

The unique properties of aerogel provide many new applications for buildings. Because of its very low thermal insulation and optical transparency, aerogel can be applied to the covers of panes and solar collectors. Due to its noise-reducing thermal conductivity and low acoustic properties, aerogel can be used in buildings, as well as adsorption and catalysis in indoor air purification, photocatalysis in environmental cleaning, non-combustion (inorganic gas) in kitchen fire panels. Aerogel materials can also be used for building walls, attics, floors and appliances. The unusual properties of aerogel open up new opportunities for its use in buildings. Their main benefits include: good insulation provides energy and savings due to reduced loss of indoor hot air or air conditioning; a healthier indoor environment due to the removal of airborne pollutants; Due to the non-combustion and acoustic properties of aerogel, it has heating and sound insulation properties. Most importantly, they are user-friendly, recyclable and reusable.

5. Application of aerogel in construction

1. Roof: Aerogel insulation can isolate the roof cavity and can also be used to reduce the thermal bridge of the roof beam. It can be used in highly insulated homes, sealed from the outside, under masonry and tile, and it has a high island value.

2, frame: In a typical building, the frame (25% of the building envelope) is not insulated, resulting in heat loss through the bolts. Insulation prevents this "thermal bridging" and increases thermal properties up to 40% for steel bolts and 15% for wood bolts

3, Floor: The thermal efficiency of aerogel insulation, good compression strength and thin profiles make it attractive for underfloor insulation, where height is a problem. It installs quickly under the floor without damaging door fittings, while providing substantial energy savings. Aerogel insulation is a fast, cost-effective solution for basement renovations that is easy to install, improves thermal comfort, and does not damage door fittings by being so thin. It can be installed quickly and improves the thermal comfort of the house. If used with radiant floors, it saves energy and enables a fast heating cycle.

Aerogel as a super insulator: Aerogel is a transparent material with high optical properties, such as high light and solar transmittance, but unlike transparent materials commonly used such as glass, it also has good thermal insulation properties; It's actually used as a solar collector and a transparent wall for the office. Energy-efficient Windows: In addition to the low thermal conductivity of silicon aerogel, high solar and daylight transmittance is achieved. In fact, by using passive solar energy through Windows, it is possible to reduce exposure to cold weather.