A problem I had after putting in new windows and insulation was when I had a fire burning in the fireplace smoke would come into the living room if I turned on the stove vent fan or I started the clothes dryer.The house was so airtight after the improvements that the fireplace was starving for air so I took the ash dump inside the firebox and cut the top off and welded a firescreen on top then I took the outside ash cleanout and drilled 30, 1/4 inch holes in it to let fresh air come into the firebox.Problem solved ! A fresh air intake is a must for airtight homes.