We often get asked about wind noise in the chimney, and how to prevent it. Noisy chimneys can be very annoying, and when you are tucked up snug and warm in your home you don’t want to be reminded of how ferocious the weather is outside!
What causes wind noise in a chimney?
You could think of your chimney as a giant musical instrument. The wind blowing across it or blowing down the chimney is causing it to make all kinds of noise. Just like a recorder in the wrong hands – it may be a musical instrument but it doesn’t necessarily make music.
Sometimes wind noise is caused by wind blowing across the top of the chimney. This is the equivalent of blowing across the top of a bottle, only bigger and louder. Some customers say that it’s worse if they have a chimney cap fitted. This has small holes in it for ventilation, so these act like the whistle holes in a giant recorder.
Another type of chimney noise caused by wind blowing across the top is an increase in airflow up the chimney. There’s usually a constant flow of air up the chimney due to the stack effect. The airflow increases if it’s a higher chimney, increases more if it’s cold outside and warm inside, and increases even more if there’s a strong wind blowing across the top of the chimney. So on a cold windy night when you’ve got the heating cranked up, there is going to be a tremendous rush of air travelling up the chimney, and this will exacerbate the wind noise in the chimney.
Another cause is the roaring noise of wind blowing straight down chimney and echoing like an ill-played bassoon.
Finally, there is simply the noise of the wind roaring through trees or howling round the roof tops, and as having an open chimney is like leaving the window open, apart from the amplification of wind noise in the chimney, you will be hearing the noise from the great outdoors finding its way in.
What can be done about wind noise in a chimney?
The simple answer is: stick a sheep in it! The thick layer of wool will muffle the sound. It will also cut off the flow of air that is being caused by the stack effect, diminishing the noise of roaring air as it flows up the chimney. The Chimney Sheep will also block out external wind noise (and other external noises such as traffic, aircraft, industrial noise and so on).
Will the Chimney Sheep block all wind noise?
It really depends on the chimneys. I’ve fitted them in properties when it’s been really windy, with the wind roaring down the chimney, and the wind noise has stopped as soon as the Chimney Sheep is fitted. By plugging the gap, effectively closing the opening, you will stop wind whistling down the chimney, you will stop the pull of air up it, and you will physically muffle the wind noise.
In other situations the Chimney Sheep will muffle the wind noise but not block it out completely. Some customers fit a layer of sheep wool insulation over the Chimney Sheep to increase the amount of sound insulation. And some use a Chimney Balloon in combination with a Chimney Sheep to reduce the impact of the noise.
Will the Chimney Sheep be sucked up the chimney by the updraught?
If you’ve got a good snug fit then the Chimney Sheep should hold itself firmly in place, and the heavier ones will stay no problem. However if it’s extremely windy then there’s a risk of one of the lighter ones (a 10” round in a 9” flue for example) being dislodged by a powerful updraught. In such a situation it’s recommended to attach a piece of string to it and secure it to a heavy object in the grate, just to be on the safe side.
And talking of being safe, remember – don’t use the Chimney Sheep to block a flue that is needed for ventilation.
Can a Chimney Sheep be used to stop wind noise in a wood burning stove?
Normally you should not need a Chimney Sheep in a wood burning stove. So long as the rope seal around the doors is in good condition, the draughts will be sealed off. However even with the doors shut there can be a tremendous wind noise down the stove pipe, and in that circumstance we can supply specially-made mini Chimney Sheeps that fit the pipe to muffle the noise. Drop us an email to find out more.