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Aerogels are open-porous, high-performance thermal insulation materials that can be used for very thin building insulation. So far, the application conditions of these materials and their potential in heritage buildings have not yet been described comprehensively. This review shows the technical properties of commercially available aerogel materials – such as blankets, boards and renders – and their use scenarios in heritage buildings, taking into account the heritage criteria of authenticity, integrity, reversibility and compatibility. Additionally, historic buildings that were refurbished using aerogels are presented. The study by theoretical evaluations and calculated U-values indicates that superinsulating aerogel materials have an exceptional potential in the refurbishment of heritage buildings. The presented examples show the feasibility of refurbishments with aerogel and the resulting improvements in terms of both comfort and thermal properties. Hence, aerogel materials are well suited to be used in preservation of heritage objects according to generally known rules and conditions of heritage preservation, thus contributing to the reduction of energy consumption in the building sector.

Research on sustainability in the building sector currently focuses mainly on technical solutions while little attention is given to how behaviour influences the uptake of these solutions. Bounded rationality may have a significant impact on the effective implementation of more sustainable technologies that are already available. However, empirical evidence on the effects of bounded rationality in the building sector, such as cognitive biases, is still lacking. Here, we present an empirical investigation of four cognitive biases in the building environment, namely the framing, anchor, default, and decoy effect. For that, energy-related decisions situations were presented to approximately 270 participants in an online survey. Our results show that awareness of greenhouse gas emissions from buildings can be raised through framing that the willingness to pay more for an energy-efficient home can be increased by presenting it as default, and that the choices can be shifted towards more energy-efficient appliances by using a decoy. The hypothesis that anchoring increases the willingness to pay more for the installation of a solar system could not be supported. These findings decrease the lack of empirical data on cognitive biases in the context of buildings and further indicate the potential of choice architecture in the building environment. The influence of cognitive biases in energy-related decisions should be used to increase the adaptation of sustainable technologies.

Silica aerogel is the ultimate thermal insulator thanks to its record-breaking low thermal conductivity (λ), open porosity and hydrophobicity. Silica aerogel's thermal conductivity is lowest at intermediate densities (ρ ≈ 0.11 g/cm ) and, because of the strong, power-law dependence of the E modulus on density, this rather low density so far led to low E moduli. Even with polymer reinforcement, increasing stiffness is only possible at higher density, thus higher conductivity. This paper explores the synthesis of silica aerogel granules using ambient pressure drying to provide enhanced mechanical stiffness whilst maintaining thermal conductivities well below 20 mW m K . The aging and drying conditions affect the interplay between mechanical and thermal properties, and are varied to optimize the physical properties. The dense (ρ≤0.29 g/cm ), but superinsulating (λ≈15 mW m K ) silica aerogels presented in this paper challenge the community's understanding of heat transport in aerogels, and do not rely on polymer reinforcement. The underlying microscopic structural parameters affecting the mechanical and thermal transport properties are investigated by modelling and simulation of the aerogel back-bone. Short aging times reduce the cross-section of, and heat transport through, inter-particle necks, leading to an overall decrease in thermal conductivity through the solid skeleton (λ ). In addition, short-aged gels undergo a partial pore collapse during ambient pressure drying of the pore fluid due to less aged, hence weaker network structures. The resulting denser structure contains additional point contacts that increase stiffness, by up to an order of magnitude. However, heat transport through these newly formed point-contacts is limited and the gas phase conduction (λ ) is further suppressed due to the even smaller pore sizes. Strong and superinsulating particles are ideal fillers for aerogel composites, concrete and renders. The optimized APD aerogels, available as granules, are finally compiled in a composite thermal insulation board with an effective thermal conductivity down to 20 mW m K with improved strength: a 2-fold increase for E, compared to a board produced from classical silica aerogel granulate. The possibility to improve mechanical properties of pure silica aerogels can help aerogels to break into new high-strength, superinsulating structural applications needed to reduce carbon emissions of the built environment., Acta Materialia, 213, ISSN:1359-6454

In comparison to conventional thermal insulators, superinsulation materials (SIMs), such as silica aerogel or vacuum insulation panels, provide a similar insulation performance at half to a quarter of the material thickness but this superior thermal insulation performance typically comes at a significantly higher material cost. However, under certain conditions, the use of superinsulation materials in building walls allows for the creation of additional floor space. Here, we derive a simple equation to quantify the cost to create such additional space using superinsulation materials as opposed to conventional thermal insulators. The equation has six independent variables, namely the thermal conductivity and cost of the superinsulation and conventional insulation materials, as well as two building geometry parameters. Notably, the cost to create additional floor space is independent of the heat transfer coefficient (U-value) of the wall. The real estate price distributions within major cities around the world are presented in order to compare the cost to create additional space with the potential financial benefit. The analysis of typical construction types, combined with the real estate data, shows that, from a financial perspective, the use of superinsulation such as silica aerogel or vacuum insulation panels (VIPs) is already clearly profitable in several major cities globally. Improvements of the production processes of superinsulation materials and the associated reduction in costs will be key drivers to make superinsulation materials economically feasible for many other locations in the future.

Insulating bricks constitute an interesting alternative to the common approach of a layered construction as they incorporate both the structural and the thermal functions of the building envelope. Different types of insulating bricks are commercially available using air, mineral wool, EPS or perlite as a filling material, with thermal conductivities as low as 70-90 mW/(m·K). In this study, we substituted the perlite filling of a commercially available insulating brick with a novel, highly insulating aerogel compound in order to further reduce its thermal conductivity. We determined the thermal conductivity of the perlite- and the aerogel-filled insulating bricks using both a guarded hot-plate setup and thermal simulations. The results showed a pronounced decrease of the thermal conductivity from 91 down to 59 mW/(m·K), corresponding to a U-value of these “aerobricks” of only 0.157 W/(m2·K). Thus, with an aerogel filling, the thickness of insulating bricks can be reduced. This entails space savings and new architectural possibilities.

This manuscript provides a bird’s eye view on energy in buildings. We discuss how energy policy leads to building standards that affect innovation in the building sector. We review current and future materials and solutions for the building envelope (insulation and glazing), renewable energy generation and energy storage, and demonstrate how the integration of buildings into district networks mitigates problems arising from a building’s, and its users’, dynamic behavior. Buildings account for ~40% of global energy demands, and the increased adoption of innovative solutions for buildings represents an enormous potential to reduce energy demands and greenhouse gas emissions. Here, we critically review the current and future materials and solutions for the construction sector. We describe how policy affects innovative businesses and the adoption of new products and solutions. We investigate how the building envelope and user behavior determine building energy demands. Compared to conventional solutions, superinsulation materials (vacuum insulation panels, silica aerogel) can achieve the same thermal performance with drastically thinner insulation. With low-emissivity coatings and appropriate filler gasses, double and triple glazing reduces thermal losses by an order of magnitude. Vacuum and aerogel glazing reduce these even further. Switchable glazing solutions maximize solar gains during wintertime and minimize illumination demands whilst avoiding overheating in summer. Upon integration of renewable energy systems, buildings become both producers and consumers of energy. Combined with the dynamic user behavior, temporal variations in energy production require thermal and electrical storage and the integration of buildings into smart grids and energy district networks. The combination of these measures can reduce the energy consumption of the building’s stock by a factor of three.

Perception of ambiguous figures is unstable and alternates repeatedly between possible interpretations. Some approaches to explaining this phenomenon have, so far, assumed low-level bottom-up mechanisms like adaptation and mutual inhibition of underlying neural assemblies. In contrast, less precise top-down approaches assume high-level attentional control mechanisms generalised across sensory modalities. In the current work we focused on specific aspects of the top-down approach. In a first study we used dwell times (periods of transiently stable percepts) and the parameters of dwell time distribution functions to compare the dynamics of perceptual alternations between visual (Necker cube) and auditory ambiguity (verbal transformation effect). In a second study we compared the endogenous alternation dynamics of the Necker cube with parameters from two attention tasks with different regimes of temporal dynamics. The first attention task (d2) is characterised by endogenous self-paced dynamics, similar to the dynamics underlying perceptual alternations of ambiguous figures, and we found clear correlations between dwell time parameters (Necker cube) and processing speed (d2 task). The temporal dynamics of the second (go/no-go) attention task, in contrast, are exogenously governed by the stimulus protocol, and we found no statistically significant correlation with the Necker cube data. Our results indicate that both perceptual instability and higher-level attentional tasks are linked to endogenous brain dynamics on a global coordinating level beyond sensory modalities.