Its pretty hot where I live too (Las Vegas) and I do not run the a/c all day due to electric prices, I will only run it at night an sometimes at the heat of the day if I must. I have found some good ways to keep my chinny cool, first I have moved his cage into my closet and close to the ground due to heat rising and the closet is nice and shaded, I put ice trays on top of his cage in the middle of the day, I put his chin chillers fresh from the freezer in his cage, I remove his wheel and I shut the closet door to keep heat out. I have yet to have a problem, during the day it stays around 75-80 in my home if it goes past 80 however I will turn on the a/c for my chins well being. Since you have no a/c you really need to watch your chins, and do not count on that fan for nothing.. keep them in the coolest place of the house, get some ice trays or even bags of ice on top of the cage during the day. If you get a few chin chillers or even some marble you can cool in the freezer and put it on the top floor of the chin cage then put the ice on top of the cage it will create a nice cool area for the chins.