air accelerating upon closing of door is what you want.
to prevent inside air/heat from going up chimney. ash dump has been converted to main fresh air intake.
after insert gets up to temps, note how much smoke comes out of chimney. if insert is burning very clean... you should see almost no smoke coming out during full operation. my chimney has little to no creosote buildup after two seasons of use for 100% heating of a 2500 sf single level home.
next up is adding a secondary burn system. newer epa stoves are more efficient by using a secondary burn system.
was getting ready to fab my own JUCA copy... out of frustration of not being able to get one for 3+ years. When JUCA finally agreed to make me one.
evidently several folks have successfully built JUCA copies. mostly due to non availability of JUCA units. basic constructions plans/information are posted on JUCA's site.