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Glazing transparency provides buildings with valuable solar energy during periods of colder weather, thus contributing to the mitigation of climate change. However, this same transparency also leads to heat loss which can offset heat gains. Although the use of insulated glazing addresses this challenge by multiplying the number of glass panes, at the same time it reduces the solar factor and thus the heating potential. This article aims to estimate the potential for passive solar heating in Europe according to the energy performance of glazing.This potential is undoubtedly a valuable resource for sustainable architecture. However, an analysis based on regional weather conditions shows a wide disparity in the energy savings that can be expected from a south-facing facade. These savings are most often well below a building's average energy consumption and so a balance has to be found between the thermal resistance and the solar factor of glazing. In addition, the carbon footprint and cost of the most efficient glazing can considerably extend the environmental and economic payback time of a retrofit.This research shows that the potential for passive solar heating is significant but only as long as each architectural situation is analysed according to its specific context and function. This potential would be even greater if windows were designed and used as adjustable facade elements to suit variations in weather and use.

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Making cities resilient and sustainable is only possible if the energy consumption of buildings is reduced. Retrofitting is one of the main tools of the environmental policies developed in cold and temperate climates, leading to the replacement of products considered inefficient. This is particularly the case for glazing, which is a key element in the energy system of a building. However, most of the glass waste generated by renovation is landfilled while the development of a circular economy in the glass industry seems today highly challenging. This paper studies barriers and opportunities to increase the recycling and repair of insulating glass units. To do so, we follow three approaches: a literature review, a series of interviews and a case study of a glazed office district in Brussels. This article provides a comprehensive overview of the main issues relating to the management of glass waste in the building sector and underlines the importance of economic instruments to support the spread of sorting and recycling practices. The need to rethink the systems for assembling insulating glass units with a view to facilitating the sorting of their components also appears as a necessary and stimulating path.

The growth of Western urban landscapes in the aftermath of World War II brought new standards of com-fort and convenience; one of the emblematic products of this modernization was glazing. Openings became larger, enhancing transparency and bringing abundant light; however, they also led to considerable heat loss. It became imperative that glazing play a part in insulating buildings. This article traces the history of glaz-ing insulation across the second half of the 20th century. Focusing on case studies of residences in France and Belgium and industry archival material, this article analyses the wide variety of glazing products that were developed between 1950 and 1990. Although all of them significantly improved thermal comfort, each conditioned the relationship between indoor and outdoor climates in a different way. In response to increas-ing demands for energy efficiency, sealed insulated glazing ultimately became ubiquitous, bringing about a profound transformation of our relationship with our environment.