lux or southern-exposure

On many old brick buildings across England, one might find the notice bracketing window-sills of “Ancient Lights.”

Dating back to 1663 and then later codified after the Great Fire, the property rights law stated that if a window providing occupants of tenement natural light for a period of twenty years unimpeded, then neighbouring properties could not be granted permission to build or landscape in a manner that might obscure said ancient window, but the onus was on the owners to mark it as such. Throughout the Victorian era up until modern times when home were electrified, there was a lot of serious study devoted to the minimum candlepower (lux) that humans needed to be kept in humane conditions. Be sure to visit the link up top to see a gallery of strategically placed portals. Maybe there is something more to be found beyond these thresholds.