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Chimneys, Flues and Ventilation
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Q1.
What type of chimney or flue have I got?
Q2. Do I need to have my existing
chimney lined?
Q3. What size of chimney or flue
do I need for burning solid fuel?
Q4. Will I need to get my chimney
swept?
Q5. Will my chimney or flue require
anything to be put on the top?
Q6. I don’t have a chimney
so can I have a gas fire?
Q7. If I have a power flue fire,
does it have to be fitted on an outside wall?
Q8. My neighbour has either a balanced
flue or power flue gas fire which has a terminal and cage on
the outside wall. If I choose a balanced flue or power flue
fire, will I have to have the same thing?
Q9. Our chimney has been removed
downstairs but is still upstairs and in the loft. Can I restore
the fireplace downstairs?
Q10. Does my fire need ventilation?
Q11. Why do some fires require
an external air vent and others don’t?
Q1. What type of chimney or
flue have I got?
The type of chimney or flue can sometimes be identified by the
age of the property although it is always worth asking your
retailer to arrange for a survey to be absolutely sure. Homes
built before the late 1960’s will often have what are
called Class 1 chimneys. Homes built after that time may still
have Class 1 chimneys but could also have Class 2 flues or pre-cast
flues so you need to be certain which type you have before choosing
a new fire.
Many gas fires are suitable for installation with all three
types of chimney and flue but some are not. Check with your
retailer or installer to ensure you are selecting the correct
fire type to suit your property.
Q2. Do I need to have my existing
chimney lined?
This entirely depends on its condition and your retailer, installer
or chimney sweep will be able to give you further advice and
arrange for a simple test to be carried out to check if everything
is okay.
It is unwise to assume that a chimney or flue works correctly
simply because it is there. Testing may discover problems that
are completely hidden from view like internal damage or blockage.
If an existing chimney has to be lined remember that this may
influence or restrict your choice of fire.
Q3. What size of chimney or
flue do I need for burning solid fuel?
Burning coal, coke or wood in an open fireplace requires a chimney
or flue with a minimum internal diameter of 175mm (7 inches)
and constructed of a material specifically suitable for solid
fuel.
For burning coal, coke or wood in a stove, the size of the chimney
or flue required will be detailed in the manufacturer’s
instruction and may be smaller than the 175 mm (7 inches) needed
for an open fire.
Your retailer, installer or chimney sweep will be able to advise
you further.
Q4.
Will I need to get my chimney swept?
Yes. It’s always advisable to get an existing chimney
or flue swept or checked before the installation of a new fire
or fireplace. To contact a registered chimney sweep in your
area, go to website www.nacs.org.uk
or telephone 0800 833464
Q5. Will my chimney or flue
require anything to be put on the top?
Depending on the age and type of your chimney or flue, a terminal
or guard may be required. A terminal is usually used to ensure
adequate flow up the chimney or flue and, in some instances,
to alleviate down draught or smoking. A terminal can also provide
protection against the ingress of rain, birds seeking a nesting
site and vermin seeking warmth.
Where a terminal is not required, a suitable guard can be fitted
to deal with bird and rodent problems.
Q6. I don’t have a
chimney so can I have a gas fire?
Yes. There are currently three types of gas fire that do not
need to be connected to a chimney or flue.
Flueless gas fires are designed to work without any sort of
flue at all. Many types use catalytic converters to change the
combustion products into harmless vapour which is allowed into
the room.
Balanced flue gas fires use an arrangement that passes through
the wall immediately behind the fire that both evacuates the
combustion products and allows in air for combustion. Balanced
flue fires (sometimes called room sealed fires) are completely
sealed from the room and usually have a glass front through
which the flame effect is visible.
Power flue gas fires use a fan arrangement to conduct the products
of combustion from the rear of the fire to the outside world.
Occasionally power flue gas fires are used where a conventional
chimney or flue is too small or its performance cannot be guaranteed.
Q7. If I have a power flue
fire, does it have to be fitted on an outside wall?
No. There are some power flue gas fires where the products of
combustion can be ducted to a point on an outside wall up to
7 metres away from the fire.
Q8. My neighbour has either
a balanced flue or power flue gas fire which has a terminal
and cage on the outside wall. If I choose a balanced flue or
power flue fire, will I have to have the same thing?
Both balanced flue and power flue have to have a terminal on
the outside wall which, depending on its height above ground
level, has to be protected with a cage to prevent people coming
into direct contact with the terminal which can become very
hot.
Q9. Our chimney has been
removed downstairs but is still upstairs and in the loft. Can
I restore the fireplace downstairs?
Yes. It is possible to replace or rebuild the chimney breast
downstairs but great care must be taken to establish how the
original removal of the chimney breast was carried out and completed.
A chimney breast that rises through a house is often a structural
component and its full or partial removal may have required
new components to be added that could affect its rebuilding.
Such restoration may require Building Control approval from
your local authority and their advice should be sought before
undertaking such work.
Q10. Does my fire need ventilation?
Apart from electric fires, all open fires, irrespective of their
fuel type, need an adequate supply of air to burn properly.
Restricting the air for combustion may cause the fire to burn
incorrectly and increase the risk of it producing toxic combustion
products. It may also reduce the effectiveness of the flue or
chimney.
In some cases, the ventilation can be from the room itself and
does not require an air vent through an outside wall and your
retailer or installer will be able to advise you further.
Q11. Why do some fires require
an external air vent and others don’t?
Quite simply it depends of the type of fire you want to have
installed. Fires that consume the least amount of gas may be
able to draw sufficient air from the surrounding space to work
perfectly. The surrounding space is itself ventilated around
the tiny, almost invisible, gaps around doors and windows and
this ‘adventitious’ ventilation is enough for some
fire types.
However ‘adventitious’ ventilation is not adequate
for all fire types so check with your retailer or installer
before making the final decision about the fire you would like
to have fitted.
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