We started a remodel of our bathroom. It is a 1949 built house, one level with partially finished basement. After we did the demo, we got concerned about entering the attic to do any venting. It is an older home with vermiculite insulation. It is a small bathroom with one outside wall where the shower/bathtub combo covers that entire wall. Is there a way to vent out the wall or down through the basement and out that wall so we can avoid the attic? The basement directly below is unfinished.
There are wall mounted bathroom vent fans like this. I don't think going down through the basement would work as well as the wall unit.
No matter what you end up doing install a push-button timer to control the fan rather than a switch. You can reduce almost all mildew / mold concerns if you leave a fan running for 30 minutes after a shower.