Single skin flue pipe is usually used to join the stove to the chimney. Even with twin wall systems a length of single skin flue pipe is often used first as it can look better (depending on the stove of course), and also gives a little heat back tot he room. We recommend a maximum run of 1500mm in single skin flue pipe. Any further and you have cooled the flue gases down which increases tar deposits, which increases your risk of chimney fire.
If in doubt please do contact us - our flue designers will help you to design a safe installation.