Chimney blocking balloons etc.

[ericmark]

I have a chimney in living room over an open fire, in the summer I use it to exhaust the air conditioner unit, works far better than putting pipe out of a window, so don't want to permanent block the chimney, also may light a fire at Christmas.

I don't know how much heat goes out of the chimney from the central heating? and if even worth doing anything to block it, but seem to remember some thing about special balloons to temporary block chimney when not in use.

What are your thoughts on these please, is it better to make a wooden panel etc.

 

[flameport]

I don't know how much heat goes out of the chimney from the central heating?

A huge amount. Imagine a permanently open window the size of the chimney.
Now consider that it's far worse than the open window because warm air rises.

What are your thoughts on these please,

Buy one of these, problem solved.
https://www.chimneysheep.co.uk/product-category/chimney-draught-excluders/

 

[ericmark]

I made a wood unit to block the chimney and it has made a huge difference once the central heating reduces temperature over night, there was a 2°C at least between upstairs and entry floor now they are equal.

 

[lostinthelight]

I wedged a dustbin bag with rockwool inside in ours, can’t see the point of buying something when free works