The terminal or top of your chimney is a very important part of the system. Terminals include things like pots, cowls, birdguards etc.
There are 100’s of designs. Cowls and guards offer increased resistance to the flow of combustion gasses and depending on your chimney, the best terminal is often an open pot. It is however sometimes necessaryto fit a guard or cowl. Please note: If there is any chance that smokeless fuel will be used, any guard or terminal must be made of stainless steel or it won’t last long.
For a variety of reasons many terminals do not conform to building regulations for live chimneys and can cause problems when using solid fuel. They are often fitted by people who are unaware of the regulations – your builder or roofer may be excellent but do they really know the building regulations for solid fuel fires? If the terminal is incorrect or damaged it can interfere with the passage of poisonous gasses and can be immediately dangerous. Many terminals are not fitted properly and prevent sweeping through the pot or risk being dislodged. Professional sweeps encounter these problems almost every day. I can advise you of the correct material, design and fit of terminal.
The terminals below are for unused / decommissioned chimneys only
NEVER USE THESE WITH A LIVE FIRE
The terminals pictured below should also not be used on live fires.
These balloon guards are often used as a cheap alternative to a proper bird guard. The mesh size is too small and this reduces the flow of gasses. It is prone to becomming blocked, particularly in cold weather. They are not normally secured so your sweep will either not clean the pot (sometimes the dirtiest part) or push it off the top. Bird droppings, seeds and even bits of bread will enter the chimney and it won’t keep rain out. When it eventually corrodes, the remains will fall in to the chimney and this can be dangerous. All in all, not good. If you have one of these, replace it with a proper guard with strap fittings.
This popular guard is also wrong. Starlings and sparrows find their way in and I’ve lost count of the number of customers who have had this problem. Bird droppings, seeds, rain etc. will fall into the chimney. Again it is not normally secured and again it can corrode and fall in to the chimney.
The pictures below show what can happen when the wrong terminal is fitted. They are reproduced here with the kind permission of Craig Forster, Chimney Sweep, Kent.
Cowls for “downdraught” problems
The problems of “downdraught” or cold air comming down the chimney are not uncommon. The reasons for downdraught are also not well understood by many as there are often multiple factors involved. Solving the problem requires some investigation and questioning regarding each individual case. Some of the factors are: Chimney height, terminal position, terminal design, building architecture, proximity to other structure including trees & hedges, chimney temperature, internal building layout, forced air extraction etc. etc. It can get complicated so you need someone who understands all this to advise you. It is unlikely that fitting a cowl will increase the draught of a chimney, indeed the added restriction will most likely reduce the up-draught further. Fitting a rotary type cowl can solve the problem but only if the problem occurs when it is windy. The best solutions for inadequate draught are relining with an appropriate sized liner for the appliance, increasing the chimney length or installing a chimney fan (last resort).
Thatched property terminals: We are happy to advise but you should ultimately follow the requirements of your insurance company.