We've seen it probably more than 100 times. In an attic, the bath fan discharges directly into a pile of insulation. You would be surprised that it's more common than many people realize!
If you don't know the condition of yours, it's worth a quick investigation. So, what are the indicators of a properly ventilated bathroom? Here are a few tips.
1. Select the correct size bath fan. Many have a square footage chart included at time of purchase, but there are tables available online as well, such as this one from HVI:
2. Ensure adequate make up air can reach the fan. As pictured, allow a minimum of 3/4" clearance under the door, and even more if possible. Use caution, however, that hollow doors only have a small solid rail at the bottom which could limit the cut off.
3. Always terminate the ductwork to the home exterior. In the photo, the duct is attached to a pre-cut galvanized sheet, and connected with a 4" starter collar. It is attached directly under a roof static vent which was installed solely for this purpose.
4. How long to allow a fan to run post-showering? The Home Ventilating Institute recommends that a fan should be left on for 20 minutes after a shower to thoroughly clear humidity and to ensure moisture and condensation in the fan body or ducting is minimized. A preset timer, such as illustrated in the attached photo, helps achive this.
5. Not sure if your fan is drawing air? As pictured, you can give it a quick (albeit not scientific) test using a sheet of paper. if your fan is blocked by insulation, the paper likely will not stick.
Commented on Nov 27, 2012
My powder room is not vented and usually smells horrible. The toilet also is constantly
plugged up. Nobody should have to use a plunger as often as I do. I have no idea of what needs to be done to fix it. The room is in a former carport. Over the packed dirt is a heated floor with ceramic tiles. Above is the upstairs and since this was a former cape code with multiple renovations, going straight up through the roof is impossible. Any ideas of what needs to be done?