This case study presents an analysis of a lighting issue observed in a high-rise 5 stars hotel in Colombo, Sri Lanka. The hotel consists of multiple storeys a fully glazed façade. The issue was identified in luxury guest rooms situated on two adjacent floors, where complete darkness is required during daytime when architectural lighting is switched off and blackout curtains are closed. Despite these conditions, the rooms were observed to be dimly illuminated, creating discomfort for guests and failing to meet luxury hotel blackout expectations.