Abstract
Windows have been a subject of interest for research in building industry due to their multifaceted and significant implications for indoor environmental quality and energy use. In this context, the present contribution explores the retrofit opportunity toward retrofit of casement windows via application of vacuum glazing. The first scenario included conductive and convective heat transfer processes. The second, more detailed scenario took, in addition, the effects of (long-wave) radiation phenomena into account. The main objective of the present contribution is thus to contrast the results obtained from primarily conductive and convective computations with those that involve a detailed coupled conductive, convective, and radiation simulation. The study benefits from a CFD (Computational Fluid Dynamics) model to evaluate the airflow patterns (temperature and velocity) within the window’s interstitial space by assuming isothermal boundary conditions. Based on simulation results, the thermal performance of the retrofitted casement window (with vacuum glass applied as external pane) can be compared to the conventional construction. Thus, benefits in terms of reduced energy use and surface condensation risk can be documented.
Highlights
Energy consumption associated with buildings has a considerable impact on the environment [1]
The present contribution explores the retrofit opportunity toward retrofit of casement windows via application of vacuum glazing
These results suggest that the retrofitted casement window exceeds the minimum temperature factor value according to the applicable regulation in Austria [23]
Summary
Energy consumption associated with buildings has a considerable impact on the environment [1]. Regarding thermal insulation of windows, designers should consider special attention toward improving the pertinent properties of the frame and glazing [4]. The cavity of box type windows is not sealed like an IG (Insulating glass) unit, and it is formed not by small spacer bars but with the distance between two layers of sashes. In order to reliably estimate the heat transfer intensity through a box window, the consideration of the convective and radiative heat transfer in the cavity and conduction in the solid bodies of the frame is necessary [6]. Recent studies suggest that traditional casement windows can be thermally retrofitted by installing vacuum glazing instead of float glass in external or internal wings. Thereby, the focus of the studies was predominantly on conductive heat transfer and applied thermal bridge analysis of the conventional and retrofitted casement windows [7]
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