How to stop the downdraught in a chimney

But chimneys can occasionally cause problems too, from excessive heat loss to chimney fires and more. One of the most frequent issues that people experience with their chimneys is a downdraught.

Downdraughts are generally caused by negative air pressure, which can be caused by all sorts of things, from a chimney stack that’s too short to overhanging trees and more. This negative air pressure can mean that air is sucked into your chimney rather than being let out, causing smoke to enter the room should you have the fire lit. This can be dangerous and you could be breathing in carbon monoxide that is usually carried out of the chimney and expelled outside.

If you believe that you have an issue with downdraughts, you can find out more below about what causes them and how to prevent them. 

How do I stop the draught down my chimney?

Warm the chimney properly

As we’ve briefly explained above, chimneys rely on pressure to carry the smoke out of your home that’s caused by burning various fuels, such as wood and coal. Sometimes, the smoke can be carried back into your home if you haven’t allowed the chimney to heat up properly first.

Therefore, to start a fire, you should first light some newspaper or kindling. Doing this allows the chimney to slowly heat up. As the heat rises, it can create a good draught in the chimney, allowing the smoke to climb out the top. As the fire gradually heats up, you can begin to add your logs. If you have a log burner, it’s best to close the door at this point to really ensure that the fire gets hot and creates a good draught. Once the fire is up to temperature, you can top it up with more logs as and when needed.  

Fit an anti-downdraught chimney cowl

A chimney cowl is traditionally made from red clay, such as terracotta, but modern versions can also be made from metals, such as aluminium and stainless steel. You will likely have seen these placed on the roofs of houses, but may not necessarily have realised what they are called or what their purpose is.

They are fitted to the chimney pot and, depending on the type that you buy, can have different functions. Usually, people have them installed to prevent downdraught, to avoid birds from nesting inside the chimney and blocking it and to prevent debris as well as rain and snow from getting into the chimney.

The primary reason for having a chimney cowl installed is to prevent downdraughts. A cowl works by encouraging the smoke to exit the chimney instead of travelling back down and potentially into your home. However, the type of cowl you will need could depend on the main reason for the downdraught. Other factors may need to be considered too, such as the type of fuel you burn, the age and style of your property and even the area in which you live (different areas can have different styles and designs of cowl, and you may want to stay in keeping with other houses).

Some cowls can rotate in the wind, too. They’re made so that one half has a small gap that allows the air to get in and rotate, while the covered half faces the wind to prevent it from going down the chimney.

If you’re unsure which type of cowl you need, there are plenty of experts that will be willing to help you. Installing a cowl is a relatively cheap fix, and should solve your downdraught problems. 

Check the height of your chimney

Chimney height can be a cause of downdraughts, particularly in one that’s too short. This is because short chimneys generally allow more wind in, as it blows across the roof and into the chimney. Therefore, to prevent this from happening, most chimneys should be at least three to four feet tall. If your chimney is shorter than this, you may wish to look into making it a little bit taller to prevent the draught from getting in.

Sources:

https://brewercowls.co.uk/blog/chimney-cowls-guide/
https://www.cuttingedgefirewood.com/news/fireplace-downdrafts-how-to-fix-and-prevent-this-common-problem/
https://www.chimneyproductsdirect.co.uk/why-is-smoke-filling-your-room/