Each bathroom has its own exhaust fan.
Bathroom vent discharge into attic.
Sizing a bathroom fan can be somewhat tricky as the information out there is all over the place.
The bath should be vented by either a 20 cfm continuous vent fan or a 50 cfm vent fan that is intermittent or switched.
Dumping bathroom exhaust into an attic or under roof space invites costly mold contamination frost under the roof in freezing climates moisture damage to roof sheathing possibly even plywood delamination or rot roof failures and shorter roof shingle life.
In order to accomplish this the roof has to have a hole cut in it.
A lot of options.
This involves running ductwork from the fan usually though an attic and out through the roof.
Allowing the exhaust to vent into your attic can potentially cause several moisture problems.
M1507 2 exhaust air from bathrooms and toilet rooms shall not discharge into an attic crawl space or other areas inside the building.
Each fan vents separately out the roof.
Both bathrooms are vented by a single in line fan that has one exhaust vent running through the roof.
It may also violate a shingle warranty.
Leaking and damaged vents as well as improperly installed ones also can cause problems.
The exhaust needs to vent outdoors.
Rusted fixtures condensation from moisture laden air can cause health and structural problems as well especially when the bathroom vents discharge moist air into attics or crawl spaces.
Exhaust air from toilet rooms and bathrooms shall not discharge into attic crawl space or other areas inside building.
If you re simply replacing the fan the ducts should already be set up for you.
Exhausting of the bath vent fan must indeed be to the building exterior.
It is because of this that many builders tend to advise against this method.
M1501 1 air shall not be exhausted into an attic soffit ridge vent or crawl space.
Now where the discharge point is is going to be up to you.
No you cannot vent your bathroom exhaust fan into the attic.
So what you want to do is you want to install a duct a vent duct and you can use flex duct for this.
One in line centrifugal fan can be mounted in the attic to exhaust the moisture from two bathrooms.
Health and structural issues when a bathroom is not vented properly.
Through the roof or an exterior gable wall.
That will take it from the bath exhaust fan to a discharge point.
Options for venting a bathroom exhaust fan include best to worst.
You should never exhaust the bathroom fan directly into the attic.
When venting a bathroom exhaust fan make sure to vent the air to the outside rather than into your attic where it can cause mold and mildew to form.
