As a southern European, roller blinds or shutters are necessary for survival. What most people used to AC don't realize, is that ANY light brings in heat. Roller blinds have holes in them that get closed only when you roll them down completely: if your house is somewhat cool, leaving them down with the holes open gives enough airflow while keeping most of the heat out. If you have AC, it's even better, you don't need much light to see inside.