I have a Harman insert that was professionally installed 2 yrs ago (replacing an old Whitfield insert). The old SS flue liner was inspected and found in good shape to reuse. The stove runs great. Now it's summer and I'm growing plants under lights in the unfinished basement. I needed ventilation for them, so I connected a duct fan to a second unused ceramic-lined flue to push air up the chimney (there was an old 6" connector in the basement where a previous owner once had a wood stove). This seemed like a convenient solution since the casement windows don't open and there's no other easy way to exhaust the basement air. At first everything seemed great, and the basement air smelled much better! But the next day I started to notice a funky smell upstairs. I realized I probably created negative pressure in the house which is pulling the basement exhaust down the adjacent flue up at the chimney down to the fireplace with the pellet insert. Is there an easy fix for this situation? TIA for any ideas!