The glass experts at Read Consulting performed a window defect analysis on defective windows at a hotel. The windows began to appear dirty, and no amount of cleaning could remove the “dirt”. When initially installed, the insulated glass (I.G.) windows appeared normal. However, over time they began to appear perpetually dirty. Using a microscope to look through the glass from surface 1, it appeared that surface #2 was heavily scratched. The window was disassembled and surface #2 was examined directly with a microscope. The defect was found to be in the Low-E coating on surface #2. This is a manufacturing defect and not the fault of the building owners. Product liability rests solely with the manufacturer.