Here is a answer to a question we get asked all the time about if you should have your chimney flue lined & why we will    only fit stoves with liners.
We regularly get asked this question so this article is intended to cover the main points you need to know.
ining a chimney with a flexible stainless steel chimney flue liner is now common practice for most reputable installers, but  we still get people coming to our showroom and asking why they can't just fit a register plate, put a vitreous flue pipe   through it into the chimney and seal all around it?
This is even more common from people who are replacing an open fire with a woodburner, as they reason that if the  chimney was OK for that, why not for a stove?
Basically, the answer is that an open fire was sending 80% or more of it's heat straight up the chimney and in doing so it   was driving the smoke and flue gases upwards - thus aiding the natural "draw" of the chimney. However, modern wood   burning or multi fuel stoves are 75% or more heat efficient - meaning that only 10% or so of the heat is going up the   chimney and is therefore not as efficient in driving the smoke and flue gases up and out.
Therefore, a typical stove fitted with just a flue pipe poking up through a register plate is sending flue gases into a cold   chimney, where they can quickly cool and, instead of going up the chimney, they settle back on top of the register plate justabove the stove.
These gases are still flammable, so any tiny spark getting into the chimney can immediately ignite the fumes and start a  deadly chimney fire.
As if that isn't enough, a natural by-product of burning solid fuels is Carbon Monoxide - an odourless and colourless gas which is deadly and kills dozens of  people every year. If that is sitting above the register  plate and your seals are not intact, it can easily seep back into the  room. This is also why it is a REQUIREMENT of the  Building Regulations that you have a Carbon Monoxide Alarm installed  in the same room as the stove.
Most reputable installers will not even consider doing an installation if the owner isn't lining the chimney, as they will not   be willing to put the signature on the required safety certificate with the risks above already known.
So for your own safety & for the stove to work to its maximum capabilities always get your flue lined.