My house is pretty well insulated and like you, it gets hot outside, so we keep our windows closed most of the time. I initially set up an air line to go outside in the attempt to raise PH. I had very minimal results with that... Im assuming that the air outside of my house is pretty high in CO2 concentration. I was also scared of some sort of pesticide or bug spray getting into the air and killing stuff in the tank. I then added a CO2 scrubber from BRS and have liked it greatly.
After some research I found people adding air lines out of the skimmer cup into the inlet line to the CO scrubber before circling back to the skimmer air intake. That actually has an opportunity to keep the CO2 media moist (which makes it work better) and also recirculating air with lower CO2 content, which makes the media last longer. Let me see if I can pull some pictures of my set up.
As a word of caution, you do have to make sure your skimmer cup does not overflow as getting the CO2 media wet is bad... Moist is good, wet is bad.