(3) Prevention of ‘Backflow’

When using an open fire or wood burning stove to heat a room, the smoke rises through the flue to the chimney pot. Generally the warm air from the fire will rise up the chimney and escape through the chimney pot. However, in strong winds, the force of the wind may overwhelm the updraft and push the airflow back down the flue. Smoke will then fill the room it is intended to heat posing a health and fire risk, causing discomfort and dirtying furnishings in its path.

A chimney cowl or cap is normally a metal attachment that fixes to the top of a chimney pot. They are an optional accessory for your open fire or wood-burning stove and some 80% of chimneys don’t have them. However as a registered ICS chimney sweep, I would always recommend the fitting of a chimney cowl, especially if you are going to have a gas fire or wood burning stove installed. There are a number of potential advantages to having a chimney cowl.

These advantages include:

(1) The Prevention of Blockages

Blockages are usually caused by birds either nesting or falling down your chimney and getting stuck in the lining. This is a far more common than a lot of people think. This is very dangerous with wood or solid fuel fires and even more so with gas fires. 

Cowls, Caps and Cages

Blockages can prevent the free-flow of air in your chimney or flue and can result in a build-up of deadly gases that are unable to escape, eventually leading to carbon/monoxide poisoning for the inhabitants.
Sometimes, a nesting bird can fall down into the wood burner or open fire. A distressed, confused bird flying around your room can be a nuisance at best but even stressful and upsetting if they also cause damage to decorations and furnishings.
A chimney cowl will prevent birds from entering your chimney and ensure they set up home somewhere safer.

Essex, Suffolk, Herts, London

 (4) Improvement of 'Draw'

There are a variety of conditions where you may find that a chimney may not suck the fumes up the chimney flue as well as it should, this suction is often referred to as the ‘draw’. Certain types of chimney cowls can improve draw and cause hot air and fumes to be more efficiently taken up by the flue pipe.

(5) Stop the Escape of Sparks and Embers

A chimney cowl helps prevent large embers or sparks that travel up the chimney from landing on the roof or dry grasses potentially causing a fire. A wire mesh around the cowl will contain the sparks allowing them to die out without causing harm.

A range of options are available and I can discuss and agree with you what is most suitable for your requirements. Please call for more information.

 (2) Keeping  Rain Out

Gas fires or wood burning stove installation usually require a flue liner. A flue liner is essentially a metal pipe running from you chimney pot all the way down to your appliance. This can act as a chute for rainwater to run straight down your chimney and into your gas or wood burning stove. A cowl would act as an umbrella over the top of the flue, preventing the water running down it.
Sometimes rainfall can create damp patches on chimney breasts inside the home. When the stove is in regular use in the colder parts of the year, the damp will usually evaporate. However, rain from even occasional showers in warmer months when the stove is not in use can collect in flue systems or the stoves themselves. Eventually, this can lead to rust.
These damp patches may even be noticed in upstairs bedrooms or loft conversions.

Samuel James Chimney Sweep