Frequently Asked Questions
How much more efficient is a wood-burning
stove than an open fire?
A simplistic answer puts the efficiency of an open fire at around
15% - 20% and a stove at up to four times that - say 80%. But
this is a bit of an "apples and oranges" conundrum;
the two appliances differ considerably in their output characteristics.
In practice, many people find that they heat their homes to a
higher more even temperature with a stove and get more warmth
into the rest of the house - all on the same amount of fuel or
less than they previously used in their open fire.
How does wood compare with other
solid fuels in terms of heat output?
It has roughly half the calorific value of coal and its derivatives,
but is far more reactive. This is demonstrated when dry kindling
is burned; the fuel ignites at a low temperature.
You can turn a woodstove up or down according to need and get
an immediate response. And wood needs little air to burn completely
to a fine ash which gives it the edge in combustion efficiency;
the less air you have flowing through the stove the less heat
you lose up the chimney.
By comparison, coal is not particularly well suited to domestic
use. It is burned most efficiently in the "pulverised fuel"
process used in power-stations, by which it is ground to a fine
powder and sprayed into a combustion chamber and burns rapidly
at a very high temperature. Even this technique merely boosts
efficiencies to those easily achievable with wood in a well-designed
I have been told to avoid steel
stoves and stick to cast iron. Is this sound advice?
No. Steel and cast iron are virtually identical in terms of heat
transmission and resistance to 'burnout' - the important thing
is the thickness and quality of material used. You may want to
consider other pros and cons though. Cast iron stoves are offered
in a range of embellished and coloured enamel finishes.
Steel stoves are of necessity plainer in appearance but don't
ever fracture (cast-iron can develop hairline fractures, particularly
if a stove is heated up too rapidly from cold.)
Another material used in stove construction is soapstone - popular
in the United States but less often seen in Europe.
If you buy from a manufacturer with a sound pedigree or take
the advice of your woodstove agent you shouldn't have to worry
what materials your stove is made from. Most 'cheap & cheerful'
products disappeared years ago!
I burn a mixture of coal and wood
in an open fire. If I buy a stove can I continue to burn these
two fuels together?
Many people do, and seem to be happy with the results. There
are one or two points to consider though.The most important is
that mixing fuels can significantly shorten the life of the boiler
if your stove is equipped with one. Much of the coal now imported
into the country has a high sulphur content. Burning wood inevitably
produces water vapour. Mix these two things together and you
get sulphurous acid which will condense onto the nearest cold
object it reaches - typically the boiler.
Secondly, a stove that has been optimised to burn wood will not
burn coal at the same efficiency. "Multifuel" stoves
attempt to get round this problem by allowing you to operate
the grate and air controls in different ways to suit the fuel
you are burning. This compromise works well enough for many people
but can never be as efficient as a "pure" woodburner,
or a "pure" solid fuel stove run on the appropriate
What about mixing wood and peat?
No problem. Peat is a marvellous fuel for stoves, either on its
own, or mixed with wood. It is particularly good for those long,
slow burns you need at the "fringe" of the season when
you simply want to take the chill off the air. The only drawback
is that peat produces a large volume of very fine ash so you'll
need to de-ash the stove at more frequent intervals.
I want a central heating stove that
will do hot water and heat a kitchen, bathroom and three bedrooms.
Can you suggest something? No! Before
that question can be answered you need to measure the length,
breadth and height of each room, and jot down other details.
Whether windows are single or double glazed. Number of outside
walls for each room (a room on a corner with two outside walls
will lose more heat than its neighbour with one outside wall.)
Finally, note down the type of outer wall construction - timber-frame,
24" (60cm) stone, or 11" (275cm) cavity brick.
Take this information to your local stove agent and ask him to
'short-list' the stoves he recommends in writing, bearing in
mind the fuels you intend to burn.
If you want to do this bit yourself, borrow a book on domestic
heating from the local library and work through the simple arithmetical
formulas. It's then just a matter of checking your figures against
stove brochures to find what "fits."
Whatever you do though, don't buy a central-heating stove "blind"
even if the price seems tempting. A wrong choice could result
in your sitting room being swamped with excess heat from the
stove whenever you try to get the bedroom radiators hot - or
else the opposite happens and the rest of the house overheats
before your sitting-room is warm.
Getting the sums right is the most important part of buying a
stove so don't take unnecessary chances!
I have a problem with poor chimney
draught and smoke coming back into the room. Should I fit a cowl?
Chimney cowls are best suited to curing "blow-down"
of the type that occurs in certain wind conditions. They may
also help temper excessive draught in an exposed site (the Aerocowl
has a good track record.) However, if you have problems in "still-air"
conditions the chimney itself needs to be looked at closely.
Is it correctly matched to the appliance? Is it of adequate height?
Is there a blockage?
The other thing to consider is that if the chimney has been out
of use for some time it may have become cold and damp, in which
case simply bringing it back into service may clear up the problem
You can often speed things up by "priming" the flue.
This involves lighting a modest fire at its base with newspaper
and dry kindlings in a manner that leaks as much heat up as possible.
But before you do this check that there is no heavy build-up
of soot or you could start a chimney-fire.
If the problem persists call in your local stove agent or chimney
The chimney-sweep has been and he
says his brushes are having no impact at all on the heavy deposits
of soot in my chimney. What's the answer?
Assuming you have a brick or stone chimney, your best hope is
to free things up with some chemical flue powder - available
from your local stove agent or hardware store.
Use the chemical in accordance with the manufacturer's instructions
and only with dry fuel (moisture neutralises the chemical, rendering
it ineffective.) Continue the regime for as long as is necessary
and you should find the carbon deposits convert to a loose dry
powder that is easily removed.
The problem is more serious if you have a stainless steel chimney
or liner since chemical flue powders should not be used with
these systems - they can damage the metal. Make sure your sweep
uses the special polypropylene brush but if this fails to do
the trick you may have to replace the affected components.
Take the experience as a warning that you are doing something
seriously wrong which needs to be changed. In particular you
should avoid long slow burns (ie, overnight) with damp or unseasoned