I cleaned my chimney and cap. within 3 or 4 weeks the cap plugged up and smoke started coming in the house. I got on the roof and see the cap was plugged up. Cleaned it again. Today I noticed the fire not wanting to burn well so up I went and sure enough about 3/4 plugged up. This is a quadrafire 7100 I only burn pine which I know creates more creosote but is this normal? Is my cap a poor design? Any advice or help is appreciated.