To install ducts in an existing home, cut a vent hole between the joists in the ceiling, using the vent cover as a guide. Build a frame above each hole for the vent boot, and connect flexible duct hose to the vent boot using metal tape and metal zip ties. Nail the vent boot into place, and seal the hole inside the room. Connect the other end of the flexible hose to the main duct trunk.
When connecting the vent boot to the flexible pipe, pull the insulation layer back carefully, and attach the pipe to the vent boot using metal tape. Then, pull the insulation back down, and secure it in place on the vent boot with a metal zip tie.
To connect the flexible hose to the rigid duct trunk, cut a hole in a piece of rigid duct board, using the start collar as a guide. Place the start collar in the hole on the board, and seal the connection with metal duct tape. Place the flexible hose on the start collar.
Secure the pipe to the start collar with metal tape and a metal zip tie by repeating the process used when connecting the pipe to the boot vent. While installing the new duct, avoid sharp bends or kinks in the metal hose, as this prevents proper air flow.