Zephyr Breeze I Use, Care And Installation Manual page 8

NEVER exhaust air or terminate duct work into spaces between walls, crawl spaces, ceiling,attics or garages. All exhaust must
be ducted to the outside, unless using the recirculating option.
Use single wall rigid Metal ductwork only.
Fasten all connections with sheet metal screws and tape all joints w/ certified Silver Tape or DuctTape.