There are two different types of pellet stoves. One is a free-standing stove, and the other is a fireplace insert. The installation of a free-standing stove is particular to the manufacturer of the appliance. Most free-standing appliances can be installed using a direct vent system that passes through an outside wall.
Pellet stove inserts installed into a fireplace also have specific manufacturer installation instructions. While some pellet stove manufacturers do not require an insulated liner, the liner manufacturer requires the liner to be insulated in order to meet the UL-1777 listing, which requires insulation for all solid fuels in order to be code compliant. Over the years our experience has shown that an insulated liner for a pellet stove results in better burning performance of the appliance with with less ash build-up.