Glass curtain walls (GCWs) are favored in building construction for their significant daylight provision, yet they present complexities such as heat flow and visual discomfort. In libraries, the integration of artificial light with daylight further complicates matters, diminishing daylight’s energy-saving potential. This arises questions if maximizing daylight in libraries contribute to energy savings, or even if the adoption of GCWs in libraries is truly a sustainable choice. This paper examines a GCW study space in KTH library, Stockholm, Sweden, to address these questions and understand how Nordic users perceive GCWs in libraries. The study involves on-site user interviews and surveys correlated with illuminance levels to validate subjective perceptions. Based on the findings, adjustments are proposed to achieve a balance between reducing energy consumption and increasing user visual comfort and mood through daylight and artificial light integration. Results indicate that Nordic users appreciate GCWs in libraries primarily for their daylight provision. Despite complexities, GCWs are viewed as sustainable especially when this balance is maintained.