Re: FRA airport is very nearly in compliance with this law....
> And my architecture text tells me that when heating was first introduced in London theatres, they were able to maintain the temperature at 12C
Well yes, but they were made of sterner stuff back then. Heck, I remember my mother telling me that as a girl in the depths of winter in the more-recent 1950s, she'd have - if she was really lucky - a single bar of an electric fire in her bedroom. Getting ready for school on those cold mornings was a matter of dressing under the bedclothes and then hopping quickly out of bed to hunch over the electric heater. We are spoiled these days by central heating & air-con.
Speaking of the Victorians and theatres, here's an informative documentary on how actors were treated back then.