Roof venting

What is going on

Roof vent. Keep a set height over snow. Seal the roof penetration. Leaks here mean wet ceilings. Too tall and the pipe gets exposed to wind and frost. Too short and snow buries it. Canada needs more snow clearance than the US.

Likely causes

• Vent too low, buried by snow
• Vent too tall above the roof, unsupported in wind
• Unsealed roof penetration leaking
• Combustion air inlet not meeting the dimensions in the figure
• Rain cap ribs left in place restricting flow

Check in this order

1. Keep at least 12 in clearance above the highest expected snow level (18 in in Canada).
2. Keep the vent no more than 24 in above the roof.
3. Seal a 2 in PVC vent through the roof using a 2 in electrical conduit flashing. Lubricate the flexible seal before pushing the pipe through.
4. Use a roof flashing boot (field supplied) and a support (field supplied) as needed.
5. Use the combustion air inlet with the roof vent, meeting the dimensions in the venting figure.
6. Remove the ribs from the cap where a rain cap is used.
7. Check for leaks in the attic after the first heavy rain.

More furnace guides

• Abnormal conditions and protection
• Adjust gas valve manifold pressure
• Air for combustion and ventilation in non-direct vent installs
• Airflow adjustment check
• Airflow and temperature rise check
• Bottom return filter rack installation (upflow)