Abstract

The application of superinsulation materials (SIM) reaching thermal conductivities far below 20 mW/(mK) allows the construction of relatively thin building envelopes while still maintaining a high thermal resistance, which also increases the architectural design possibilities for both new buildings and refurbishment of existing ones. To accomplish such a task without applying vacuum solutions and their inherit weaknesses may be possible from theoretical principles by utilizing the Knudsen effect for reduced thermal gas conductance in nanopores.
This study presents the attempts to develop nano insulation materials (NIM) through the synthesis of hollow silica nanospheres (HSNS), indicating that HSNS may represent a promising candidate or stepping-stone for achieving SIM. Furthermore, initial experiments with aerogel-incorporated concrete and the conceptual work concerning NanoCon are presented.

The main aim of this article is to rephrase good and bad performance of built environments as good or bad interplay of spaces, building technologies, and users. To support this perspective, two conceptual tools broadly used within the social study of technology are introduced. These concepts, the semiotic pair “script/antiprogram” and the study of “domestication of media and technology in everyday life,” were originally developed in the search for a better understanding of the mutual shaping of culture/society and technology. In this contribution, these concepts are applied in an empirical study of two nonresidential buildings. Through an extension of these concepts, consequences for the creation and maintenance of better built environments are proposed.

Due to the significant impact of the building sector on greenhouse gas emissions, newer and stricter regulations aimed at reducing total energy use in buildings have appeared in the last few years. In the European context, all the new constructions will thus soon be asked to be nearly Zero Energy Buildings (nZEB).

In order to reach this target, new concepts and technologies capable of further improving buildings’ energy efficiency need to be developed. A very promising strategy to overcome current technology limitations is represented by revisiting the conventional approach that considers the building as a static object and moves towards the vision where the building is a responsive and dynamic system. The main feature of this concept is the possibility of continuously changing the interaction between the building elements and the outdoor/indoor environment in order to reduce the energy demands and enhance the exploitation of “environmental” and low-exergy energies.

In this framework, the building skin is probably that element of the construction which shows the largest potential, especially if its properties can be continuously tuned so that the best response to different dynamic indoor and outdoor boundary conditions can be achieved. Although it is not possible to state that the dynamic building envelope alone could represent the only solution to achieving the nZEB target, great expectations are placed on advanced integrated façade systems.

The aim of this research is therefore to evaluate to what extent dynamic and active building skins can reduce operational energy demand in buildings. In order to find an answer to such a wide (and general) question, the research activity is organized using a multi-level structure. Each segment of the investigation is thus dedicated to assessing the impact of such a vision on different scales: from a whole building skin approach (concept level) to an intermediate scale (system level) and further down to a very detailed and specific class of components (material-technology level).

In the concept level, an ideal dynamic building skin is assumed and modelled. The performance of such a theoretical configuration is then numerically assessed and compared with that of a more conventional reference envelope solution. In the system level, an integrated multifunctional façade module, characterized by a high degree of adaptability and responsiveness, is presented, and its energy and thermo-physical behaviour evaluated by means of an experimental analysis. Finally, in the material-technology level, the implication of glazing systems integrating phase change materials on the energy performance and on thermal comfort are evaluated by means of experimental, numerical and laboratory analyses.

The findings demonstrate that improvements in energy efficiency and comfort performance can be achieved when dynamic concepts, systems and technologies are applied. In every level, the dynamic component often provides a very good performance and, when compared to a conventional solution, advantages are shown. However, it is important that dynamic components are coherently employed in the framework of an integrated building design vision and properly managed. Further, the simple adoption of such systems without a global approach and optimal control strategies is often not enough to reach a significant improvement in energy efficiency and IEQ. The results also show that, sometimes, the advantages achieved by the investigated configurations may be lower than expected, though an optimization of their performance is probably still possible.

Limitations in the analyses and possible solutions for future development of the research activity are also discussed, pointing out that, if from the one hand, considerable efforts are still needed in research and development before a completely adaptable building skin can be effectively employed on a large scale, on the other hand the large potentials that this vision has are worthy of further investigation.

Smart windows like electrochromic windows (ECWs) are windows which are able to regulate the solar radiation throughput by application of an external voltage. The ECWs may decrease heating, cooling and electricity loads in buildings by admitting the optimum level of solar energy and daylight into the buildings at any given time, e.g. cold winter climate versus warm summer climate demands. In order to achieve as dynamic and flexible solar radiation control as possible, the ECWs may be characterized by a number of solar radiation glazing factors, i.e. ultraviolet solar transmittance, visible solar transmittance, solar transmittance, solar material protection factor, solar skin protection factor, external visible solar reflectance, internal visible solar reflectance, solar reflectance, solar absorbance, emissivity, solar factor and colour rendering factor. Comparison of these solar quantities for various electrochromic material and window combinations and configurations enables one to select the most appropriate electrochromic materials and ECWs for specific buildings. Measurements and calculations were carried out on two different electrochromic window devices, where one ECW was substantially darker than the other in the coloured state.

Abstract

Introduction of more dynamic building envelope components have been done throughout the last decades in order to try to increase indoor thermal comfort and reduce energy need in buildings for both temperature and light control. One of these promising technologies is phase change materials (PCM), where, the latent heat storage potential of the transition between solid and liquid state of a material is utilized as thermal mass. A PCM layer incorporated in a transparent component can increase the possibilities to harvest energy from solar radiation by reducing the heating/cooling demand and still allowing the utilization of daylight. The introduction of dynamic components in the building envelope makes the characterization of conventional static performance indices insufficient in giving a clear picture of the performance of the component in question.
Measurements have been performed on a state-of-the-art window that integrates PCM using a large scale climate simulator. The glazing unit consists of a four-pane glazing with an integrated layer that dynamically controls the solar transmittance (prismatic glass) in the outer glazing cavity. The innermost cavity is filled with a phase change material.
This article presents and assesses the series of measurements and the related methodologies with the aim of investigating the thermal behavior and thermal mass activation of the PCM-filled window. The experiments have been carried out using several static and dynamic test cycles comprised of temperature and solar radiation cycling. A conventional double-pane window has also been experimental investigated using the same test cycles for reference purpose.
It was found that even for temperatures similar to a warm day in Nordic climate, the potential latent heat storage capacity of the PCM was fully activated, but relatively long periods of sun combined with high exterior temperatures are needed.