For use with solid fuel (wood, coal, smokeless and anthracite) the
liner is twin wall (or twin wound) and made of stainless steel with an
expected service life of approximately 15 years. A chimney fitted with
a liner MUST STILL BE SWEPT ANNUALLY AS A MINIMUM.
Liners offer significant advantages over masonry flues and have
only one significant drawback. If the flue opens into a sizable cavity
bigger than the standard 9" flue it is advisable to line to decrease
the amount of condensate the large flue can cause to form.
Does my chimney need to be lined?
HETAS advise that a liner is a 'temporary solution to a defective
chimney'. It is not essential to line a chimney before use but in many
cases it is advisable. If a loft conversion has been carried out a
flue liner is generally recommended as the builders often compromise
the masonry in the process of conversion.
How can I establish if my chimney is sound?
I would advise getting Sean Wilson the
Brighton Chimney Sweep 07973 512 189
to sweep and pressure test your flue. If Sean is busy or booked up we
can do the assessment of your flue.
Sean Wilson The Brighton Chimney Sweep
07973 512 189. Sweep and
pressure test. |
£80
approx. |
| Hanover Builder flue test
follow this link for details of our flue test. |
£120 |
|
We offer £30
discount on a liner or a cowl if you have this test done and
subsequently book us to fit a chimney liner or
cowl |
Can a liner be installed without scaffolding?
In most cases yes. We use a combination of ladders to reach the
chimney stack. In many cases as well we do not need to remove the
chimney pot either.
I have an open fire can this chimney be lined?
Yes. But it can present some problems. The minimum liner size is 7"
diameter. This can be near impossible to fit in some 9" (standard)
chimneys. A gather (a stainless steel hood) also needs to be fitted so
usually the fireplace needs to be removed and refitted afterwards.
I already have a liner which was put in for a gas fire, can this be
used?
No. Gas liners are single skin stainless steel. Solid fuel liners are
twin wound (often referred to as twin-wall). A gas liner would
function for a time but will fail quickly due to the acidity of the
gases emitted by solid fuels and the higher temperature achieved.
What is the significance of the liner diameter?
Flexible metal liners commonly come in three diameter sizes; 5"
(125mm), 6" (150mm) and 7" (175mm). Building regulations forbid
narrowing of a liner after the stove spigot. So the stove spigot
effectively dictates the liner diameter used. Smoke control appliances
with outputs under 20kW, burning wood (sometimes called DEFRA approved
appliances) are capable of using 5" liners. Open fires must have a 7"
liner as a minimum.
What guarantee does the liner have?
Different manufacturers offer different guarantees. I fit Midtherm and
Schiedel liners which carry a 10 year manufacturer's guarantee.
www.hanoverbuilder.co.uk/stoveinstructions.php
Does a liner 'increase efficiency'?
Many manufacturers claim this to be the case. I think these claims
needs to be carefully understood. A liner usually increases chimney
draw, this is measured in pascals (Pa).
Most manufacturers specify a minimum Pa requirement. A typical
chimney produces a draw of something between 10-20 Pa. Increasing the
draw beyond manufacturers requirements is unlikely to add to the
stove's efficiency and a liner will slow conducted heat transmission
in the rooms through which it travels.
So the answer is nuanced and it depends what is understood by
'efficiency'. However a liner will almost always increase chimney draw
which can lead to efficiency gains.
What is 'backfilling' and do you do it?
Backfilling is filling the void between the liner and the masonry
flue with extruded mica called 'vermiculite'. This is an inert, heat
resistant material and a very good insulator. We do backfill on
occasion, usually on north facing exposed flues, very rarely on
terraced houses. Based on 5 bags required for a typical two story
property we can backfill for an additional
£200.
Backfilling can present some problems when liner replacement
becomes necessary.
Can you line my chimney before I decide on my stove/open fire?
Yes, but this is usually impractical. The liner is best installed
with an appliance in mind. Namely a 7" liner with gather for an open
fire, a 6" for a stove and a 5" for a DEFRA approved appliance.
What are the benefits to having a chimney liner?
- Increase in draw
- Decrease in the likelihood of leaks of harmful gases
- Possible increase in stove efficiency
- Better sweeping, ease of service
- Less condensate in flue
- 10 year guarantee
What are the drawbacks?
A
chimney liner is intended to remedy a defect in a masonry flue
(erosion from acidic gases, cracks in the masonry, loose pargeting
etc.) without the difficulty and expense of having to undertake
extensive building work.