How to draught-proof your chimney

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 several factors such as:

• the height of your house
• the difference in temperature between inside and outside

For example, let’s say you live in a tall house, you have the heating on and the it’s cold outside. This means there’ll be a bigger ‘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’ll also use less heating, which is a win win, reducing your bills and impriving your carbon footprint. 

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

First up is getting a draught excluder: a useful device fitted inside the chimney or around the fireplace. This stops the warm air going up and the cold draughts coming in.

This is your cheapest option at around £25. And you’ll soon make the money back. We’ve calculated that a chimney draught excluder can save you £60 a year in Great Britain (GB) and £65 in Northern Ireland (NI).

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.

Make sure you remember 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).

The other option is getting your chimney fitted with a ‘cap’, normally made from terracotta. This provides better insulation and protection from:

• moisture
• birds
• draughts

It’s a more expensive option that needs to be done by a professional. We always recommend getting quotes from at least three tradespeople to get the best value. Also check if the tradesperson is a member of a trade association or a competent persons scheme.

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