I had a similar problem in my previous house which didn't have central AC. The insulation in the house was great for about one day. But in an extended heatwave,

I had a similar problem in my previous house which didn't have central AC. The insulation in the house was great for about one day. But in an extended heatwave, outside 100F meant eventually inside 90F. I got decent cooling results with two separate window fans, opposite sides of house, one blowing in one blowing out. Of course, all other windows are closed. Depending on your window frame style, these types of dual fans fit inside a window frame and don't leak air. They can be set to: both in, 1 in 1 out, both out. So quite flexible. https://www.amazon.com/Bionaire-BW2300-N-Reversible-Airflow-Control/dp/B000065DKJ https://www.amazon.com/Bionaire-BW2300-N-Reversible-Airflow-... A single window fan of the above style can cool a single room quite well, blowing cool air in and blowing hot air out. As others have mentioned, depending on breeze and temperature, opening all the windows can sometimes work better than multiple fans. Fans are just no substitute for a real AC unit, which can lower indoor air temp to below outside air temp and can also extract moisture from the inside air.