What are evaporative coolers?
An evaporative cooler requires doors or windows open to allow airflow. As a guide, the entire volume of the room should be flushed through every two minutes (or around 30 air changes per hour).
During winter, older ducted units on the roof should have covers placed over them and ceiling vents closed to stop heat loss. Alternatively, consider purchasing a unit with a motorised damper. (many new units have a automatic spring or gravitational shutter)