On several recent inspections, I have noted bathroom exhaust fan ducts that are improperly terminated either inside the attic space or into an enclosed soffit. This is a concern because vents terminated near a roof ventilator, gable, vent, or eave vent or bird blocking might lead to reduced attic ventilation, impaired fan ducting, high humidity levels, decay and/or mildew-like staining. Below are a couple examples of my recent findings.
This bathroom exhaust fan duct was terminated inside an enclosed soffit. This house had never been lived in so there was no visible damage... yet.
Below are three other examples of missing or incorrectly terminated bathroom exhaust fan ducts.
Below are some examples of the damage an improperly terminated bathroom exhaust fan duct can cause.
Current standards call for all exhaust fan ducts to be completely vented to the exterior in a dedicated and proper roof vent and for good reason.