Reliable methods are needed for classifying the robustness of buildings and building materials for many reasons, including ensuring that constructions can withstand the climate conditions resulting from global warming, which might be more severe than was assumed in an existing building’s design. Evaluating the robustness of buildings is also important for reducing process-induced building defects. We describe and demonstrate a flexible framework for classifying the robustness of building materials, building assemblies, and whole buildings that incorporates climate and service life considerations.

Published in Journal papers

A simple, mild, and effective template approach has been used to produce hollow silica nanospheres with controlled sizes ranging from 40 to 150 nanometers. The obtained powders showed systematic variations in measured thermal conductivity, with values down to 0.024 W/(mK) so far, with en expressed goal to reach below 0.020 W/(mK). Surface hydrophobization was successfully performed. Thus, hollow silica nanospheres are considered to be promising building blocks for new hydrophobic, superinsulating materials.

Published in Conference papers

Window panes, glass structures and electrochromic windows in buildings 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 different glass fabrications enables one to evaluate and thus select the most appropriate glass material or system for the specific buildings and applications. Measurements and calculations were carried out on various glass materials, including three electrochromic window devices, and several two-layer and three-layer window pane configurations.

Published in Journal papers

Single-crystalline sodium tungsten bronze (Na-WO3) nanorods with typical diameters of 10−200 nm and lengths of several micrometers were prepared via hydrothermal synthesis. The as-prepared Na-WO3 nanorods crystallized in a hexagonal structure (space group P6/mmm) with unit cell parameters a=7.3166(8) Å and c= 3.8990(8) Å and elongated along the ⟨001⟩direction.

Chemical analyses indicated a stoichiometry of Na0.18WO3.09·0.5H2O, revealing the existence of tunnel Na+ ions and water molecules in the structure, as confirmed also by the vibrational spectroscopic study. The as-prepared Na-WO3 nanorods exhibited a direct-allowed electronic transition with band-gap energy of about 2.5 eV, which allows a visible-light-driven photochromism related to photogenerated carriers and a proton−electron double injection process. The proposed photochromism was discussed in detail by means of Fourier transform infrared spectroscopy. The involved local structural evolutions such as water decomposition and ion intercalation during the photochromic process were identified.

Published in Journal papers

Single-crystalline sodium tungsten bronze (Na-WO3) nanorods with typical diameters of 10–200 nm and lengths of several of microns were prepared via hydrothermal synthesis. X-ray diffraction data showed that the as-prepared Na-WO3 nanorods crystallize in a hexagonal structure (space group P6 / mmm) with unit cell parameters a = 7.3166(8) Å and c = 3.8990(8) Å, and elongate along the <001> direction. The Na-WO3 nanorods had a mean chemical composition of Na0.18WO3.09·0.5H2O. The Na-WO3 nanorods exhibited a typical cathodic coloration related to proton insertion, indicating their potentials in electrochromic smart window applications.

Published in Conference papers

The Research Centre on Zero Emission Buildings - Annual Report 2012

Published in Reports

Monodisperse polystyrene (PS) spheres with controllable size have been synthesized by a straight forward and simple procedure. The as-synthesized PS spheres have a typical diameter ranging from ~180nm to ~900nm, where a reduced sphere size is obtained by increasing the polyvinylpyrrolidone (PVP)/styrene weight ratio. The PS spheres function as sacrificial templates for the fabrication of hollow silica nanospheres (HSNSs) for thermal insulation applications. By modifying the silica coating process, HSNSs with different surface roughness are obtained. All resulting HSNSs show typically a thermal conductivity of about 20mW/(mK), indicating that the surface phonon scattering is probably not significant in these HSNS samples.

Published in Journal papers

One of the most effective actions for reduction of energy loss through the building envelope is to optimize the thermal performance, area and localization of the transparent components in the façade in order to obtain minimal heat losses and optimal solar gains.

When considering the thermal performance of these transparent components, one should consider, not only heat loss (or gains) caused by thermal transmission, but also the beneficial effects of incident solar radiation and hence reduced demand for heating and artificial lighting.

This study presents calculations for a range of windows as part of a building where the coupled effects of incident solar radiation and thermal transmission heat losses are accounted for in terms of a net energy balance for the various solutions. Effects of varying thermal transmittance values (U-values) are studied in connection with solar heat gain coefficients.

Three different rating methods have been proposed and applied to assess the energy performance of several window configurations. It has been found that various rating methods give different energy saving potentials in terms of absolute figures. Furthermore, it has been found that windows, even with existing technology, might outperform an opaque wall in terms of heating and cooling demands.

Published in Journal papers

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