Questions covered in this guide
Identify the route as well as the roof opening
PNNL directs bathroom exhaust outdoors and describes both roof and wall outlet routes. A new-looking roof cap does not, by itself, document where the indoor fan’s duct ends or whether the complete route was checked.
Tell the roofer which rooms are involved
List bathroom fans and any known roof outlets, using existing records or accessible observations. Ask the roofing and mechanical contractors to identify the actual connections where needed. Do not climb into an inaccessible attic or disconnect ductwork to investigate. If the reroof proposal includes replacing a vent cap, ask whether its scope also includes confirming the duct connection, and identify another trade if that task is outside the roofer’s work.
Prepare a room-to-outlet worksheet
Give each bathroom a row with the fan identification if known, professionally verified route, outlet location, proposed roof work, and responsible trade. Add blanks for any mechanical or electrical work the project team identifies. Ask who checks the completed connection and what record will be supplied. Keep a proposed route change separate from a simple cap replacement so its design, permit questions, and finishing work are not hidden in a generic roofing allowance.
Verify the full handoff
At closeout, obtain confirmation from the appropriate professional that their assigned work is complete. Keep the room-to-outlet record with the roof and fan documents for later service. Do not assume adding an attic vent accomplishes the same job as a connected bathroom exhaust outlet. The national roof calculator does not assess fan performance or price rerouting work. A useful proposal names the roof interface and the indoor connection, with one clearly identified owner for each.
Putting it into practice
The guide traces a bathroom fan to its exterior outlet and assigns roofing-versus-mechanical responsibility. It prevents a roof-cap replacement from silently becoming an unsupported claim about the entire exhaust path.
Sources and supported claims
PNNL states that bathroom exhaust should discharge outdoors rather than into an attic.
Source ↗ · national · Checked 2026-10-12
PNNL describes wall and roof outlets as possible bathroom-exhaust termination routes.
Source ↗ · national · Checked 2026-10-12