The Design Challenge Stove has a sloping secondary combustion chamber, which has two big advantages:
1. You can easily see the secondary flames because the sloping fireback is clearly visible below the height of the door opening, and
2. You can easily vent into a fireplace opening. Because the secondary fireback is sloping, there is easily enough room above it for a rear flue outlet.
Most of the stoves in our target price range do not have rear flue exits, and the secondary activity is hidden above the door (unless you are on your hands and knees), because the top of the firebox is parallel to the bottom.
Check out the video below, and you’ll see why we want the secondary activity to be visible.