Clay Chimney Cowls

Here at WT Knowles, we are often asked about clay chimney cowls. It might surprise you that there is more to learn than you would think. Before we talk about clay chimney cowls, let’s start off with what chimney cowls really are.

What is a cowl on a chimney?

Chimney cowls are usually made from red clay or metal coverings that are fitted to chimney pots. There are usually three types of material used to manufacture chimney cowls, with one being galvanised steel. This is the cheapest material used and more importantly the least robust, which leads to problems such as rust or can even start to disintegrate relatively quickly.

Whereas aluminium is more highly regarded, relatively robust and will not rust and nearly as cost effective as galvanised steel. However, it is not suitable for high temperatures and melt at temperatures approximately 600°C. The aluminium will therefore become difficult to weld so the chimneys cowls generated from this material are screwed or riveted together which may cause problems in freeze situations.

Another highly regarded material is stainless steel as it does not rust but is much more expensive than the other two materials we have mentioned. Chimney cowls produced from stainless steel are suitable for high temperatures have good resistance to acid contained in smoke and are considered the most robust material to produce chimney cowls and terminals.

Chimney cowls are designed to prevent wind from blowing the smoke back down into the room below, also known as downdraught. Usually, people install a chimney cowl is for this reason. Downdraught is caused by negative air pressure, which can be because of overhanging trees near your property, or your chimney may even be here too short.

Another use is to prevent animals, such as birds from blocking the chimney by building a nest or dying inside. Chimney cowls have a lid and wire to stop birds from entering your chimney. When the winter arrives, chimney cowls are designed to guard against rain and snow entering the chimney.

Can I install a chimney cowl myself?

Yes, you can install a chimney cowl yourself, as long as you can reach the top of your chimney easily. It is important you follow instructions carefully throughout and to be careful when installing. However, if the installation is difficult, it might be worth hiring a professional to complete the job on your behalf.

The best ways to improve your chimney draught

The main way to ensure that an issue with chimney downdraught is solved is to install an appropriate anti-downdraught chimney cowl. By doing this the smoke and gases flow up the chimney and keep the fire burning beautifully and safely.

However, we have noticed an initial smoky downdraught can occur when in response to cold air in the chimney. Warming up the chimney by burning newspaper and small kindling when first lighting the fire will help hot air to rise and not be blocked by cooler air higher up.

Downdraught could still be an issue even after the chimney has had time to heat up, or happens only in windy conditions, then an anti-downdraught chimney cowl is probably the solution.