High Efficiency Furnace Venting Through Cold Air Return

[rkeaner]

My exhaust and intake vent pipes are in a terrible position for finishing my basement soffit. They run under my heat and return trunks and then up between floor joists to the outside wall. It looks like I can maintain the the correct slope if I go up and over the heat and cold air return trunks, however, I would have to go between the floor joists through one of the branches off the cold air return for a couple feet. Can I do this?

[Admin]

The B149.1-20 Gas Code would not allow this in the province of Ontario,

Clause 8.10.12 - A flue gas vent or a vent connector shall not be installed in either a duct or a shaft used for return air, hot air, ventilating air, or combustion air.

If the joist is lined and acting like a return air, you could just buy some duct board and reduce its size and box out the venting, so the venting was outside of the return air cavity.

[rkeaner]

Thank You for response.  I assumed that was the case but hoped it was not.