John Davis, owner of Springfield Steel Buildings, explains how to install a draft excluder: 'You should start off by measuring your chimney. Every fireplace is different and chimneys come in a variety of shapes and sizes.
'Place a dust sheet on the floor in front of the fireplace and put on a pair of safety goggles. You should now take the time to measure the inside cavity. If the chimney is oblong, measure the depth and width. If it's round, note down the diameter.
'Using these measurements, try to find a draught excluder of an appropriate size. Avoid fitting a generic one as it is unlikely to fit properly. Consult a size chart if you ever find yourself stuck or unable to decide.
'Once that is done, get your hands on some Chimney Sheep. This sheep's wool will serve as insulation. You'll want it to be just a little bit bigger than the chimney flue. The wool should accommodate the shape of the opening.
'Once inside, pull the handle attached to the Chimney Sheep to ensure everything is in place. If it's a good fit, the sheep's wool will remain in place.
'This is arguably the best way of draught-proofing your fireplace as the sheep's wool is breathable, blocking the majority of the airflow but still allowing around 7% for ventilation purposes. This reduces the risk of damp or mold forming, which can happen if the chimney is sealed too tight.
'If you want to use your fireplace to start a fire, simply remove the draught excluder from the chimney and put it back whenever you are done with the fire.'