Chimney Issue

[Scott W.]

The fireplace backs up; smoke enters the townhome (rented out) & has since caused smoke stains in the corner ceilings.

I met the chimney contractor inspected this morning. No blockage. Says it's a draft issue. Suggests either a vaccu stack ($500 but can't guarantee can solve the problem) be installed at chimney or an electrical powered exhaust fan mechanical draft system ($2200 - guarantees will solve the problem).

My tenant (he's a contractor as well) thought since the furnace was replaced last year (& that's when the problems with the fireplace began), that the HVAC contractor needed to cut a small square in the drywall, near the floor, next to the furnace in order to do the install.

He thinks this may be causing the draft & he could just drywall it & see if it solves the issue.

Any thoughts?