Exceeding the Applicability Limit of Aerogel Super Insulation Materials in Different Environmental Conditions

Abstract

Newly designed and constructed buildings are subjected to increasingly strict regulations which emphasize the minimization and, where possible, the elimination of wasteful energy consumption, thus resulting in a decrease in emissions. Thermal insulation materials have an important role in making better use of the primary energy delivered to consumer systems, be it by an industrial process or building services systems or in residential and commercial buildings. It is well declared that buildings account for about 30% of total energy consumption, while they contribute to about 20% of greenhouse gas emissions. High-performance insulation has great potential to achieve the European Commission’s ambitious goals for reducing the thermal loss of buildings. A new class of super insulation materials (SIMs) could play an important role in the future of insulations (e.g., fiber-reinforced silica aerogel). This material is grouped with super insulation materials by the sixty-fifth annex of the International Energy Agency. However, due to their short presence on the market, we do not know much about their long-term performance, and if their properties change with time, the question is how and in which direction they do. This is why their artificial aging is so important through thermal annealing, in addition to exposing them to high humidity and low temperatures. In this paper, the application of measurement results after the artificial aging of fiber-reinforced silica aerogel will be discussed. In order to see the changes in the thermal insulation capability of the materials, 13 different cases of environmental exposures are discussed. These cases will be presented to see possible changes in the thermal insulation performance of the aerogel after treating it in different climatic conditions. Firstly, samples were exposed to humidity treatments at 296 K with different relative humidities (0, 35, 50, 65, 80 and 90%) until they reached equilibrium moisture contents. Secondly, the samples were heat treated once for 6 weeks at 343 K, then for 1 day at 373, 423, 453 and 483 K. Moreover, we wanted to see the effects of frost, and thus we executed a freeze–thaw cycle on the samples for 25 days between 258 and 303 K. After these curing procedures, the thermal conductivities of the samples were measured with a heat flow meter, according to the ISO 8301 standard. The measured thermal conductivity values after heat treatment, wetting and freezing were used for building energetics calculations, with a special focus on the thermal transmittance of two different hypothetical building structures (brick- and concrete-based walls) covered with the mentioned insulation.