That is it, www.batticdoor.com louvers wont seal anything ,
batticdoor closes and drops down an inch for a fairly positive seal.
Louvers leak...Imaging taking 3" pvc vertical, and dropping a closed
31/6" cap on it, it seals, when dryer blows air pressure raises it, non
powered louvers can`t ever provide a positive seal of airflow. and dryer
types ive seen are cheap by design and build.