One of the first lessons from the past is that hot air rises. Seems obvious doesn't it? Believe it or not there is actually a company that is successfully convincing people that by making their air even hotter than everyone else they can do a better job of keeping people comfortable from 20 or 30 feet above them. But that is a different story for another time.
After the invention of air conditioning though we seem to have forgotten one of the key elements of this natural cooling cycle...venting the hot air out of the building. In most modern air conditioned buildings we keep the hottest air inside the building and just keep cooling it back down in a constant cycle that requires compressor or chiller energy. In many cases the hot air inside the building is still cooler than the hot air outside the building so this might make sense during the hottest months of the year. However, in the case of a data center or server room, the hot aisle air is usually much hotter than the air outside...but most data centers use cooling equipment that constantly tries to cool down that hot aisle air resulting in huge energy consumption.
Some systems also take advantage of the "stack effect" in a shorter building by recognizing that any heat source in the space will create it's own "mini stack effect". Cooler air will be drawn towards the heat source and the hot air above the heat source can be exhausted. This creates some natural circulation in the space and is one of the key principles behind "displacement ventilation".
Alton and Aztec divisions of Mestek, and they work even better than those primitive early methods. But no compressor or chiller energy is required.
American Warming division of Mestek, offer exterior solar shades that actually track the position of the sun and change angle in order to maximize the shading effect.
There are many other lessons from the past that could be discussed but the key is to stop and think about how we used to do things. Sometimes adapting ideas from the past to ideas from today can result in the best overall solution.