Analysing the environmental impact of windows: A review

Windows have a major influence on indoor comfort and are critical factors in terms of the energy consumption of buildings. Accordingly, the design and performance of window glazing and frames are key elements in the implementation of thermal regulations and contribute to the success of energy renovation policies. However, despite their multifaceted-role, there is a lack of holistic studies that bring together the environmental issues resulting from the production, use and disposal of windows. The aim of this article is to review these multiple aspects holistically and to provide a better understanding of the role that windows can play in reducing the environmental impact of buildings. As such, this paper analyses twenty-three environmental studies of windows, frames and glazing, including recent Environmental Product Declarations. It is the first study to address environmental issues related to windows from a holistic perspective considering both quantitative and qualitative studies. Through this approach, this paper outlines the methodological issues associated with the environmental analysis of windows, particularly regarding the definition of the functional unit and the quantification of impact during the use phase. Additionally, this review provides new insights into the life cycle of windows, frames and glazing by comparing the results of research carried out since 2000. The paper also defines important questions pertaining to the understudied area of the end-of-life of windows and their recyclability and reusability. Finally, this paper takes advantage of the complementarity of the reviewed studies to discuss three propositions that would support the development of an improved framework that would be suitable for the life cycle assessment of individual building elements such as windows, where energy efficiency depends both on the behaviour of occupants as well as on the rest of the energy systems of a building.