Literature Review of High Performance Thermal Insulation

The European Union has decided to decrease the energy use for heating of buildings with 50% in 2050. To reach the target the amount of insulation in the building envelope has to increase. With conventional insulation materials, such as mineral wool and expanded polystyrene (EPS), the required additional thickness of the building envelope leads to a larger share of the building area dedicated for structural elements. A number of high performance thermal insulation materials and components have been introduced to the building market during the last decades which can give the same thermal resistance using a thinner construction. This report presents how insulation materials work. The properties of aerogels and vacuum insulation panels (VIP) are described more in detail. Heat transfer in thermal insulation materials is generally divided in heat conduction through the solid material, conduction through the gas molecules and radiation through the pores. Gas convection in the material can be important on a larger material scale and in porous materials, such as mineral wool. Aerogel for building applications has a thermal conductivity of around 14-16 mW/(m•K) while VIP can reach down to 4 mW/(m•K). This can be compared to EPS and stagnant air with a thermal conductivity of 36 and 25 mW/(m•K) respectively. Aerogel and VIP have small pores in the range of 10-100 nm which means the gas conductivity is reduced at atmospheric pressure. Up till now aerogel has been used in space industry, chemical industry and in sport equipment but not that much in buildings. A limiting factor is the high cost of the aerogel. Since the end of the 1990s VIP has been used in buildings but originally they were developed for refrigerators and cold shipping boxes. To use VIP in buildings, the architects and engineers have to pay special attention to attachment details since the VIP cannot be adapted on the construction site. Nevertheless, novel high performance thermal insulation materials could be an important and feasible solution to decrease the thickness of the building envelope while maintaining the thermal resistance. These materials create new opportunities for architects and engineers to design energy efficient buildings.