Fake News and wood burning stoves

Wood burning stoves have been unfairly targeted by blogs, the press … just about everyone lately and are being painted in a very negative light. The reality, which in my view is very different to that portrayed in the press of late. So i will attempt to address the matter somewhat here in this post.

Firstly, wood is one of the only truly renewable fuels but yet is often compared to diesel due to some of the particles that are emitted when burned. Diesel is a fossil fuel derived from crude oil and although some particles are emitted during burning wood (in a bad way & in old appliances) I’m pretty sure that diesel does not produce a major percentage of the worlds oxygen like trees do.

With the massive deforestation that has takes place in recent history, ethical log suppliers are now rapidly planting trees which will help safeguard our future generations. Those same planted trees will store the carbon released from today’s log burning making the cycle neutral.

Statistics can be a funny thing and are often taken on an annual basis. As we know, the wood burning season in the U.K. is relatively short beginning late September through to the end of March/April. During the rest of the year any measured pollution does not come from wood stoves. Ironically it is the summer months when the dangerous carbon dust particles are often at their highest levels.

As far as i am aware, there are no statistics specific to wood-stoves published in the U.K. with regards to air quality or pollution. Instead statistics are based on all domestic burning of wood and its’ derivatives and includes open fires, camp fires, pizza ovens, BBQ s and bonfires. The last two in the list are some of the very worst pollutants and yet somehow only wood burning stoves are being attacked.

I understand that there is a genuine problem with the use of some wood burning stoves. There are four main issues that chimney sweeps must advise on; in regards to wood burning in order for clean combustion.

1. Moisture content and quality of wood logs.
During the combustion process it is necessary for there to be high enough temperatures within the firebox in order to burn the majority of the carbon particles. When excess water is present, the energy which would normally ignite these particles is instead utilised to evaporate the water contained in the log. This causes much of the fuel contained within the wood to not burn and is instead emitted as smoke.

**I personally always suggest you only burn sustainably sourced (preferably hardwood) logs with less than 20% moisture content. Using wood-sure logs will help as the checks have already been done but you can always invest in a moisture meter and check for yourself.

2. The way the end user burns their stove
: specifically the dangers of slumbering, over-fueling or under-fueling.

As is often with many ‘old school’ things, some strange ‘old wives’ tales have developed about how stoves should be used. It has unfortunately become a ‘normal’ practice for many to fill the stove with wood and then reduce the air supply in order to make it last through the night. The process is referred to as slumbering and it is very bad indeed with regards to air quality and pollution. Not to mention the safety and functioning of your stove +/ liner.

To use layman’s terms; if you remember the Bunsen burners in school science labs. When the air hole on the side is open the flame is sharp, blue and clean. But limit the oxygen by closing that hole and the result is a flame that becomes lazy, yellow and soots up whatever it touches.

This yellow, colder flame in also inherently more dangerous because the levels of carbon monoxide are very much higher in a reduced oxygen environment (combustion is incomplete). Limiting the oxygen results in a much lower combustion temperature meaning many volatile components do not burn when slumbering, therefore it is far more polluting.

Like all hydro carbon based fuels wood needs oxygen in abundance for all of the gasses emitted within the fire box to combust completely and cleanly. Limiting the air does not limit the gas released by the logs it only limits how much of the gas will burn.

***Users are advised to always burn the quantity of wood that the stove was designed to use and with primary & secondary air controls open enough to provide moderate flaming combustion. [This is when the entire window is filled with rolling fire and no smoke is seen but not so much that the flames can be seen sucking up the chimney.]

3. The third problem relates to the age and efficiency of the stove. It is a fact that older stoves are very much more polluting than newer, more modern appliances. ****Consumers should be advised that new appliances will save on fuel, give more heat and allow much better quality air that we breathe.

4. Finally, servicing and maintenance.
It is understood that regular sweeping of chimneys, cleaning flue-ways and servicing appliances are all essential for continued efficient combustion. Chimney sweeps should ideally ensure that stove servicing and education is a part of their repertoire in order to bring this essential service to their customers.
*****Indeed, my own advice is always to burn clean dry logs (<20%). Do NOT slumber and use the correct amount of fuel in each fill. For what it’s worth i also try to suggest clients update outdated appliances where necessary and should get our sweep service up-to two times per year.

It is the general opinion of the profession that further debates or articles should be fairly measured against all sources of pollution and not unfairly target wood burners alone. The minutiae of the fixes for wood burning stoves are simple and the industry has made great progress in these areas already.

Surely, the issue of particulate emissions rests firmly in the hands of other industries; which now need to be ethical as we have always been, engage in debate and effect change.

For example; one wonders what is being done to educate the consumer with regards to, BBQ s Chimeneas, patio heaters and pizza ovens? Thousands of these are sold each year in the UK and yet such heavy polluters never make fair target for the press? As previously mentioned they are often used in the summer when pollution is at its highest. Also consideration too, should be given to bonfires and the burning of urban dung fires which produce extreme amounts of pollution.

In conclusion, the discussion on clean wood burning needs to be addressed holistically and not simplistically target any one tiny segment of the overall market.

Beware the Daws of March.

As is customary for this time of year , i always write a wee reminder that spring is upon us once again and it won’t be long till Mr & Mrs Jack, D Aws will be scouting for a new home. Unfortunately that is most likely to be in a chimney and is one of the worst problem situations a solid fuel user can get.

Customers always seem to imagine a nest will be similar to that of a crows nest that you see in a tree. So they are almost always astonished when they realise it is more akin to a beavers dam and normally a minimum of 1.5 bin bags full of material. If they are interested i tell them my memories of the, “worst nest ever” back when i were just a young lad of about ten or so, let’s say early-mid 1980’s.

This nest was like several stories high and must have been generations returning and building on the old nests before as foundations. The run of the flu in this old building was quite funky too and presented my father and co , no insignificant problem. At some point they had to open up the bricks to make sure it was 100% cleared and in the end after 9 hours they had amassed 13 full bin bags of twigs, squashed coke cans, six inch nails, sheep’s wool, horsehair and other assorted nesting materials.

The moral of the story is , it is better to be safe than sorry…prevention is far better than cure in this case and so very much LESS expensive for you. The other thing is you should know that once you’ve got one , it cannot be removed till August unless you get a special permit. For more in depth information you can read our previous post on birds nests, filed under funnily enough ‘birds nests’

Spring/Summer Season 2019 is here

Typically , the first day back is blizzard conditions but that did not stop me. Another reason to be glad i use power sweeping rods now , far superior to the old systems including the ball and circular brush so not so much climbing as when i was the roof man for my father.

When i think back , for me i started on roofs at only 3 years old and loved climbing anyway so it was great fun and i always liked the danger aspect .. Over the years my father only had one or two good roof guys ..sure he had a lot of good workers over the years but if they could even do the job competently that was enough. It was free climbing , or running as one potential applicant pointed out his reasons for not wanting the job.
We used to do anything up to 50 sweeps in a day so one could not afford to be slow in anything , organisation with a hefty dose of courage & skill was essential.

I’d wager, even i, myself couldn’t do that now , you need to be in practice doing it every day to be able operate at that kind of level. Thing is since i lost my father i seemed to lose my invincibility too , for him i could and would do anything because he was the boss. Now i have responsibility , it limits the risks you can take because no you no show … this means in my spare time & hobbies too.

Looking forward to catching up with my regulars this season, cheers Tom

Seven years have passed

It is now the time of year when my fathers passing draws close, this being the seventh year. I will probably make this my final post on the subject, I will always love and miss him with each passing day, especially when I am out working. Sometimes, it can be hard not to remember things and times gone by.

Indeed the good old days, with no masks, just some old clothes, and a pair of half gutted training shoes, haha. There once was a time before roof ladders too and I remember being very reluctant to use it for the first 5 or so years after my father bought it. Yes, it was useful for the few jobs I felt were too risky but it was cumbersome, weighed heavy and I just didn’t like it.

When I think of just some of the many many acrobatic feats my father and I performed daily through the 70’s 80’s and 90’s I get a big warm glow inside. Just knowing that there are very few who could or would be able to do anything like what we used to do; makes me appreciate the uniqueness of the skillset we had to develop and keep polished just to survive each coming week of the season. The customers too, often we would have lovely old ladies prepare banquet sized feasts for us, amazing. Everything all prepared for us coming with military precision, no chambermaid duties for us.

I also think back to my very first climb onto a roof, which must have been 1974 because I was only THREE years old. This was near the top end of Sutherland drive in new farm loch, Kilmarnock. I actually remember that day pretty well despite it being closer to 50 years ago than I’d care to admit. I remember due to the way idiots were driving up and down the street, my father decided it was safer for me to come up on the roof with him and just sit about 3 or 4 foot up from the gutter’s edge. It really was a very slow slope anyway and I being a natural monkey, had already climbed many much more dangerous things by then.

I had been wearing my bright red welly boots that day and was enjoying the views when “long john silver” a promotion-hungry, gung~ho police ‘person’ arrived on the scene. I remember climbing back down and standing inside the customers garden gate. Also getting angry with him because basically, he was being a dick to my dad.

Anyway, luckily for us the case got dismissed in court by the infamous Sherrif D. Smith who astutely listened to my father’s honest version of events, i.e. I was never in any danger. The court reporters decided to run with the story and so I ended up on the front page of the Kilmarnock standard newspaper. The headline was I am led to believe, “The welly boot kid”

Seven years may have passed but the great memories remain forever. Love and miss you always dad.

Chimney pots, cowls and Caps

Chimney pots, cowls and Caps

This article will serve as a general introduction to various pots, their insertions, cowls, and uses.

A standard terracotta electric cap aka elephants foot or a correctly sized roll top chimney pot is usually the best way to terminate a chimney.  They are made of terracotta, have low wind resistance, are strong, last many years and most importantly do not impede the flow of Flue gases because there is no change of direction. Smoke is hot and it likes to travel vertically,  not horizontally.

Cowls /Fixings

Cowls are typically fixed in one of three ways: 

  1.  Strap fixing: this is by far the most secure and what sweeps typically recommend as it reinforces the pot and cannot easily be swept off.
  2. Bolt fixing: These types of cowling are not favoured by many, the bolts pull the pot from the inside often opening cracks. They are also very easy to sweep off.
  3. Gravity: many Terracotta inserts are held in place only by their weight. Care must be taken when cleaning them as they are easy to dislodge and Very heavy so can do a great deal of damage when landing from a fall.

It is worth noting some cowls (horizontal slats) can act as an additional 90 deg bend as the smoke is forced to change direction at a right angle before it can exit to the atmosphere. Smoke also quickly cools when it hits cold metal mesh and the top of the cowl causing creosote deposition within it. The cleanliness of cowlings should always be checked with binoculars after sweeping.

Chimney Terminals: The Rules

The internal diameter of a chimney terminal used for solid fuel open fires must be no less than 8” to comply for adequate gas flow and building regulations. Although Solid fuel terminals are typically suitable for gas the reverse is NOT true. Solid fuel terminals must be made from a material that does not easily or quickly corrode, especially where smokeless fuels are used.

Mesh Size

ANY Mesh fitted to terminals servicing solid fuel appliances must be stainless steel and the hole size must be no smaller than 2.5cm x 2.5cm.  Gas terminals often have smaller mesh and quickly block with soot when used incorrectly with solid fuel. This can cause smoking back and even carbon monoxide poisoning.

Pot inserts

Any terracotta insert that sits inside a pot has a spigot which reduces the effective internal diameter.   The spigot often makes them instantly unsuitable for open fires. There are indeed many inserts which are only to be used for disused chimneys.

One exception to the above is top hanging Cowls connected to a liner and attached to a stove. These can be as small as 5” 125mm internal diameter for some Defra exempted stoves however 6” 150mm is more typical.

Louvered Pots

Louvered pots are used to stop rain running down the flue and can be identified as the gap in the louver is quite large and they are also often formed as part of the pot. They must not be confused with GC gas cowlings that look similar but are absolutely not suitable for solid fuel.

Figure 1: Louvered pot

GC terminals have a number for identifying them GC1, GC2 etc the number usually relates to the size of the cowling and its air flow rate. Some decorative fuel effect gas fires require chimneys that are as large as those required for solid fuel. It is important that sweeps always insist gas appliances are serviced immediately after sweeping by a gas safe engineer to ensure the relevant rules are met and the customer is safe.

Figure 2: Gas Terminal/Cap GC2


H pots are one of the best anti downdraught designs, they come in two varieties; an inset which is not suitable for most solid fuel open fires and a Complete pot with the attached H that is. The inset version can be a great option for stoves that require a smaller diameter Flue. H pots have fallen out of favor because of the weight and price but really do work well for wind induced down draughts.

Figure 3: H Pots

Rotary cowlings

Rotary cowlings are designed to spin in the wind that may be causing a down draught and in doing so cause an up draught.
There are some downsides to these;
• They must be cleaned which means occasionally someone has the unenviable job of climbing on the roof to reach them.
• If the axel is even the tiniest bit bent then they will be very noisy and spin of the axis.
• They only work in the presence of the wind.
• Eventually, they will stop spinning and need to be replaced.
• They only work on wind induced down draughts and serve no benefit when the down draught is caused by positive pressure down draughts from being in a high-pressure zone. Extending the termination beyond the high-pressure zone is the recommended action for these.

Disused Chimney Plugs

These types of terminals are not for use on live appliances. It is normally the correct procedure to issue a Do Not Use warning notice when these are being used on live appliances. It is impossible to perform a satisfactory or accurate type 2 smoke test when these are installed. A standard terracotta electric cap aka elephants foot or a correctly sized roll top chimney pot is usually the best way to terminate a chimney.

Figure 4: Disused chimney plugs typical e-cap bottom rhs

Mechanical extract fans

Electrical extract fans can be used to offset positive pressure down draughts and can even make chimneys work when the pressure inside a property is a minus. Traditional chimneys rely on positive pressure inside the room where the appliance is helped push the fumes up by natural draught when combined with the heat of the fire. Occasionally, usually in public houses, there can be a minus ambient pressure situation caused by mechanical extract ventilation in the kitchens and this must then be offset by adequate intake air (vents) and/or a mechanical chimney fan.
There are some significant downsides to these  that you must be aware of:
• Only people competent to work on electrical appliances can install them legally.
• They must be manually cleaned.
• Alone they do not make the installation compliant under J regs, merely make it work.
• They require servicing.
• If they fail or the electric goes out it’s a very smoky day indeed.


So i hope you have enjoyed this wee introductory article, please feel free to share it , steal it… modify it as folks do on the interwebs. Tom