Windows provide building occupants with important physiological and psychological benefits but are absent from many indoor spaces. It is argued that most existing attempts at compensating for an absence of windows fall short because they lack either outdoor environmental information or sensory stimulation. A wind-animated digital-tree shadow was used to test this hypothesis. The work concludes that the following strategies are likely to help most to compensate for an absence of windows: (1) establishing a live connection with the outdoors; (2) introducing controllable sensory variation into a space; (3) making such change a source of natural environmental information. It is suggested that these approaches could be helpful used either separately or in combinations but that a live connection with the outdoors that introduces controllable naturally-generated change into a space would likely be most effective. The video files that accompany this thesis show the digital shadow with wind and computer generated movement.