The main environmental impact of windows is from the heat loss through them. Attention is drawn to the large number of credits available in BREEAM, the Code for Sustainable Homes and EcoHomes for reducing fabric heat loss and improving operational CO₂ emissions compared to the small number available for materials specification. The embodied impact of windows should only be taken into account as a small part of the decision, with the main emphasis being to choose a window which will reduce operational energy usage.

Windows are one of the elements with a less important role in the overall embodied impact of buildings due to their low impacts and low area within buildings. However, the narrower the plan depth, as with external walls, the greater the impact, as the surface area of the building increases relative to the floor area.

Although at a glazing ratio of 30%, windows may not seem to represent a significant proportion of the building impact, it is possible for a high percentage of the facade to consist of glazed areas, particularly in commercial developments with glazed curtain walling. In such cases, the choice of window specification can make a significant contribution to the reduction of the building's overall embodied impact.