Having an open chimney is like leaving your window open all the time.
Fitting a Chimney Balloon to an open chimney is like fitting the gap with double glazing. The Chimney Balloon is designed to inflate and push against all four walls of the chimney, holding itself firmly in place. There is a small vent in the side of the product which allows some airflow, permitting your chimney to “breathe”.
The Chimney Balloon isn’t stretchy like a party balloon, but it has double walls which enable it to keep its pillow shape when it’s inflated.
Chimneys do vary a lot so it is worth taking the time to measure yours carefully before selecting the appropriate size balloon.
Being effectively a double barrier with the top and bottom of the balloon, air is trapped inside, insulating the chimney against cold air sinking down, while simultaneously preventing warm air from rising up.
Fitting a chimney draught stopper like the Chimney Balloon stops the stack effect. Your chimney acts like a giant syphon, pulling warm air out of the home and causing cold air to be pulled in through leaky parts of the building. By blocking the chimney, you are cutting off the stack effect, retaining warm air and noticeably reducing cold draughts.