We bought a 1897 house located in the northeast. It's about 4500 sq feet. The area around the house gets very humid in the summer, so it also gets very humid inside. In fact, the house was very moldy when we moved in and we hired pros to get rid of the mold. :(
The third floor has a house fan (see pics). The former owner did not use it and stuffed the fan with foam to insulate from the outside. I turned it on and it runs. I understand it's used to cool off and dehumidify a house, which this house certainly needs. I understand they work really well.
But, the fact is, it is old technology and I wonder if it would be better to just rip it out and somehow fill up the space it took (I guess by adding another window).