We bought a home with a whole house fan system.

Here's a link with some information that may help:

https://www.wholehousefan.com/blogs/wholehousefans/5-causes-of-mold-in-your-attic-and-what-you-can-do-about-it

Here's an interesting link about whole house fans, pro's and con's and the correct installation:

https://powermepronto.com/en/the-pros-cons-of-whole-house-fans/

I never had issues with mine. The heat of the attic should allow moisture to evaporate.

My parents have had one since the early 1970's and never had any issues with mold. Even when they had a water problem under the house which caused mildew up the walls about 3', the fan was fine.

Hello, I think this video should help you out,

https://upgradedhome.com/can-a-whole-house-fan-cause-mold/

https://www.youtube.com/watch?v=CQZmWIYsyDU

I'd get in inspected and ask them!

Only if you don’t have adequate venting in the roof. There should be vent grates in the soffits in the roof overhang. Climb into the attic and pull away any insulation that may have gotten into the vents. If there are no vents, you definitely need some; a good lumberyard or contractor calm help you determine how many you need for your house.

What did your house inspector say regarding this during the inspection before you bought it?

Thank you guys for answering. We did have an inspection, but he never said anything about the whole house fans. We didn't even know what they were at first. My brother said the attic looks clean, just very insulated. There is a fan in every room upstairs on the ceiling. They had to move the electrical box because it was so old, so we are not even sure where the switch is at. I will have to take some pictures tonight and post some pictures.

here is more info for you

https://www.brcroof.com/your-attic-needs-to-breathe-too

The whole house fan pulls air in from open windows and exhausts it through the attic and roof. It provides good attic ventilation in addition to whole house cooling. Whole house fans should provide houses with 3 to 6 air changes per hour (varies with climate, floor plan, etc.—check with a professional to determine what is appropriate for your home). The air-change rate you will choose depends on your climate and how much you will depend on the whole house fan for cooling.

As long as you have a ventilation system through out the house you should be fine. I had mold in my bathroom because there was no ventilation system in the bathroom. We installed one and good by mold. The fan system should have ventilation, have it check out by a professional.

The Building Codes mandate calculated attic ventilation, but if you have an old house, then you should observe how the attic looks, on occasion.

Typically you would not draw outside air through the house if it’s a high humidity day.