1980 Vermont castings resolute, hooked up to existing fireplace when starting a fire when either top or front door gets open there is a major back draft of cold air. Then the first 3-5 minutes while starting it it smokes terribly. I have used wood stoves all my life and on other stoves I will lite some newspaper by the exit pipe to get a draft going. Doesn't work. Chimney is squeaky clean. Any suggestions?