An open chimney acts like a tall extractor fan. Warm air from the room rises up it, and cold air falls back down it, pulled by the wind and by the temperature difference. In a room with an unused fireplace this goes on all winter. A chimney draught excluder is designed to stop it.
How they work
A wool pad is a thick felted block that sits in the throat of the flue and is held by its own shape. A chimney balloon is an inflatable bag that is pushed up the flue and blown up to fill the space. Both aim to stop the flow of air without permanently altering the chimney. Our chimney draught excluders include both types.
Which one is right?
- Wool pad: best for a regular opening that you can reach, and for long-term use. Wool is breathable, which helps the chimney stay dry.
- Balloon: best for an awkward chimney that narrows and then opens up, where a pad cannot reach.
- Round pad: for a round stove flue.
How to measure
- Use a torch and a ruler.
- Measure the opening front to back and side to side at its narrowest point.
- Write both numbers down and choose the size that is slightly bigger, so it seats snugly.
- For a round flue, measure the diameter.
Getting the size right is the difference between a good seal and a pad that drops out of place.
Safety rules
- Always remove it before lighting a fire. Use the reminder tag, and keep it where you will see it.
- Never block a flue that serves a gas fire, boiler or any appliance in use without advice from a qualified engineer.
- Keep ventilation. Do not block air bricks or vents that supply an appliance.
- If you are unsure about your chimney, ask a HETAS-registered installer or a Gas Safe engineer, as appropriate.
When not to block a chimney
If the chimney is used by a boiler or a gas fire, do not block it. If you have damp problems on the chimney breast, speak to a surveyor before you fit anything, as sometimes a chimney needs ventilation at the top, such as a vented cap.
Maintenance
Check the pad each autumn for soot, dust or damp. Wool can be brushed gently. If it is wet or smells musty, let it dry in a warm place or replace it.