When should the whole-house fan typically not be used?

Using a whole-house fan during a rainstorm is not advisable because it can draw rainwater into the home. Whole-house fans work by pulling in outdoor air to ventilate the interior of the house, and if it is raining, the fan can inadvertently pull in moisture along with the air. This can lead to water damage, increased humidity levels, and mold growth inside the house.

It's important to use whole-house fans in conditions where outdoor air quality is good and dry, ensuring that they effectively help to cool and ventilate the home without introducing unwanted moisture or weather conditions that could compromise the indoor environment.