What common defect may suggest improper installation of windows?

Gaps or misalignment with the frame is an indicator of improper installation of windows. When windows are not correctly aligned with the surrounding frame, it can lead to significant issues, including air and water infiltration. These gaps not only compromise the thermal performance of the home by allowing drafts, which can increase heating and cooling costs, but can also lead to moisture accumulation, subsequently causing mold growth or structural damage over time. Proper installation should ensure that windows fit snugly within their frames with no visible gaps.

In contrast, while cracked glass panels can indeed be a defect related to windows, they do not necessarily point to installation issues; they might be due to impact damage or stress. Scratched surfaces are indicative of handling or installation mistakes but don't directly relate to the quality of the installation itself. Unpainted edges are more a matter of finishing than installation accuracy, and while they might suggest neglect, they do not inherently indicate that the window was improperly installed. Thus, gaps or misalignment are the most telling signs of installation errors among the options provided.