Exhaust Into Attic

Attic ventilation works on the principle that heated air naturally rises primarily utilizing two types of vents.

Exhaust into attic.

So you do need to get that vented outside whether it s through the siding with one of those trap doors that sort of opens out every time you ve got it on or through. You should never exhaust the bathroom fan directly into the attic. And many building codes require discharging exhaust to the building s exterior so it s just a good rule of thumb. 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.

Intake vents located at the lowest part of the roof under the eaves allow cool. Your attic is not a temperature controlled environment is never the same temperature as your living space and generally closer to the temperature outside. The best exhaust fan venting is through smooth rigid ducts with taped joints and screwed to a special vent hood. Although this isn t always possible in attic crawl spaces you should always insulate the duct to prevent condensation problems.

No you cannot vent your bathroom exhaust fan into the attic. Venting into the attic sends excess moisture to that space which can cause mold and other problems. Duct already wrapped in insulation at home centers. It may also violate a shingle warranty.