Windows are a key component in the building envelope. They are often, thought of as energy drains and something associated with excessive energy demands in a building. However, in order to assess the energy performance of a window, several factors must be addressed. The most important issues to consider are energy losses due to heat transmission through windows, energy gains from solar radiation as well as transmitted visible light and the influence on artificial lighting demands. Factors like thermal and visual comfort in buildings are additional factors that need to be assessed and addressed. Existing work that has been carried…

Abstract A crucial property for double-glazed sealed insulating window panes is to maintain their thermal insulating properties and thus low U-values. However, degradation and thus subsequent reduction or loss of low-conductance gas concentration may occur in the sealed glazing units by their exposure to outdoor climate. The choice of spacers is important to keep as low thermal transport through the window panes as possible, i.e. low U-value. In addition, the type of spacers may also influence their durability and resistance towards ageing, which hence may be characterized by the low-conductance noble gas concentration, e.g. argon, krypton or xenon. Ageing and…

Abstract This paper deals with the search for the optimal window-to-wall ratio (WWR) in different European climates in relation to an office building characterized by best-available technologies for building envelope components and installations. The optimal WWR value is the one that minimizes, on an annual basis, the sum of the energy use for heating, cooling and lighting. By means of integrated thermal and lighting simulations, the optimal WWR for each of the main orientations was found in four different locations, covering the mid-latitude region (35° to 60° N), from temperate to continental climates. Moreover, the robustness of the results was…