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How to draught proof your chimney

by Felix Davey

open fireplace in living room

Hot air goes up, up and away

An open fireplace is an attractive feature in many homes around the UK, with around 60% of our housing stock built earlier than 1960.  Open fires and wood burners aren't the most environmentally friendly method of heating your home, although a roaring fire is very comforting when it's cold outside.

But keeping our homes cosy takes more than stoking up the fire and putting on the heating. We need to keep warm air in our homes. And chimneys draw air out, whether or not the fire is going.

Exactly how much air is drawn out of your chimney depends on the ‘stack effect’, which relates to the movement of air into and out of buildings. It’s influenced by various factors, like the height of your house and the difference in temperature between inside and outside.

Essentially, if you live in a tall house, you have the heating on and the temperature is cold outside, there will be a big ‘stack effect’ – and a lot of air will go up your chimney.

As this warm air rises, it needs to be replaced. So cold air is pulled in, usually from around doors and windows, creating the chilly draught that you can feel (and hear when it’s windy).

By cutting out draughts, you can keep your home nice and cosy. You will also use less heating, which is a win win: reducing your bills and helping the planet. The climate is changing due to emissions of greenhouse gases resulting from human activity, and heating buildings currently accounts for more than a third of the UK’s emissions.

Skyscrapers deal with the ‘stack effect’ by having revolving doors instead of normal ones, to create a ‘seal’ on the building. But what can you do to draught proof your chimney? You have a couple of options…

Draft excluder

First up is getting a draught excluder: a handy device fitted inside the chimney or around the fireplace, to stop the warm air going up and the cold draughts coming in.

This is your cheapest option, with prices starting at around £15. And you will soon make the money back. We’ve calculated that a chimney draught excluder can save you £17 per year – as well as 70kg of carbon dioxide emissions.

You could go for an inflatable draught excluder, which will fit snugly inside your chimney. Just make sure that it has a small vent, so air can pass through.

Or you might prefer a draught excluder made for the specific size of your chimney.

Breathable materials like wool are best, allowing air to pass through but keeping the heat in.

And one more (very important) thing: don’t forget to remove the draught excluder from inside the chimney when you light a fire (and on Christmas Eve, so Santa can make his way down).

Chimney cap

The other option is getting your chimney fitted with a ‘cap’, normally made from terracotta. This provides better insulation and protection, from moisture and birds as well as draughts. But it is more expensive, costing more like £150.

It also needs to be done by a professional. When you’re looking for the right trader for the job, remember to follow our tips:

  • speak to friends and family for recommendations
  • check for membership of a trade association  
  • always get several quotes.  

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