05 Feb 2021

Call us odd if you like, but we do like to geek out about chimneys.

For us, understanding every nook and cranny of each chimney we work on is vital if we’re to deliver the best possible service to our customers.

But what about you? Do you really need to know all there is to know about your chimney? Well, arguably, no – that’s why we’re here. But it’s definitely worth familiarising yourself with some of the key components.

This will help if you ever suspect there might be an issue with your chimney, or if you decide to make improvements.

Today, we’re going to look at the chimney cowl. Prepare to learn something genuinely interesting!

What is a chimney cowl?

Chimney cowls are the metal or clay coverings that are fitted to chimney pots. There are several styles available, but you’ll most commonly see the circular variety which appear as little ‘cages’ on top of the pot.

There are several different types of chimney cowl, and they’re all designed to serve a specific function.

The best type of cowl very much depends on the task it needs to perform and the type of chimney to which its attached. Often, a simple, round, open pot is all you need. This is because hot gasses travel vertically, and some cowls add too much resistance, resulting in more soot.

Why should I have a chimney cowl fitted?

Firstly, it’s always best to seek professional advice before having a chimney cowl fitted. It’s an important part of the flue system, and you’d be amazed by howmany we come across as chimney sweeps that are not fit for purpose.

There are some common reasons a chimney cowl might be required:

  • up draught needs to be improved;
  • downdraught is an issue;
  • the owner needs to animal-proof their chimney;
  • weather proofing is needed; or
  • heat loss is problematic – particularly when you don’t intend to use the fireplace.

You may, of course, not need a cowl at all, but this is why it’s so important to seek expert advice before you pay to have one fitted.

For instance, if up draught appears to be an issue, there could be many reasons behind it. Lack of adequate ventilation, bad flue design and the positioning of the flue itself are common causes. Professional investigation will be the only way to ascertain whether or not a cowl will help.

The same goes for downdraught. This is when air is forced back down the chimney, and it’s often caused by wind. The area of high pressure created at the top of the chimney can sometimes be eliminated, but you’ll need a second opinion.

When it comes to animal and weather proofing, modern cowls will help significantly in preventing birds, rain and other foreign objects from entering your chimney.Bird guards and cowls with lids are likely your best bet in both instances.

What are the different types of chimney cowl?

There are six main types of chimney cowl currently on the market:

–         Bird Guards: as the name suggests, these guard against birds entering or nesting in the flue. They usually appear as a rounded mesh top with a metal lid

–         Anti-Down draught cowls: these are designed to reduce the effects of wind blowing down the flue, some have the appearance of a UFO

–         Gas Cowls: these are very restrictive and are only suitable for gas appliance, seek advice from a gas engineer. The type of gas fire and type of flue determine which type of gas cowl are permitted.

–         Rotary cowls: wind causes these to spin, thus creating a vortex that increases up draught.

–         Mechanical fans: these are used to create a vacuum, thanks to a mechanic extractor fan and are typically found in pubs or restaurants to counterbalance the effect of industrial kitchen extractions.

–         Flue cubes: these mix hot air from the flue with cold air from outside to create a mini cyclone, thus increasing up draught.

We hope we’ve demystified chimney cowls for you today, but if you have any more questions, or think a cowl could help you, just get in touch with the SweepSmart team.