I had a cap on mine for awhile; what some call a shanty cap. Flat top, four large openings, one on each side. No screening. It plugged up with creosote in short order so I took it off and the furnace performed much better. I have never seen sparks coming out, even with roaring fires. I have a 4 foot extension on mine, which may be part of the reason. Also, I keep all the coals raked forward toward the grates and most of my wood isn't any longer than the distance from the door to the chimney, so there's usually not much coals/fire in the back of the firebox. I think any kind of screen or cap will require frequent cleaning and may cut down on draft.
Last edited: