Daylighting Without Windows: The Plastic-Bottle Skylight and the Light Pipe, Their Delivered Lumens and the Bound Where They Fail

12 bottles hold 100 lux for 7.57 h on a clear day and 0 h overcast; one 350 mm pipe gives 246 lux clear noon, 31 lux dull overcast; both give 0 lumens at night. Human problem: Windowless rooms are dark at noon; people need honest delivered-lumen figures for bottle skylights and light pipes instead of clear-noon promotion.