Steve, during "the zeros" it was very trendy for IT-companies to establish offices in old, rustic factory buildings like that. In 2000 and 2001 I worked for a Swedish owned web-company, called Framfab. We worked below such windows in a former assembly plant for General Motors. You're absolutely right - it was very hot on very hot Summer days (fortunately pretty rare around here). It was very unpleasant during Winter, where most of us dressed in heavy jackets - and we had to put up a lot of heat-blowers. The pretty modern heating system was not at all adequate for our sort of work, and I don't think brim-work was significantly more physical.
I absolutely agree, that the pics, you've shown lately, clearly show surprisingly good working conditions on early 20th Century German hat plants. Probably a lot better that American workers experienced during the same periode. Not least, when we're talking ventilation, fume- and dust-control. However, this elderly and still-sitting "code-slave" gets the chills, seeing windows like that - but I'm from a lot more spoiled generation, than the workers in the pics
