…Much less your summer, fall, or winter… A leaky damper, if it is in the throat of your fireplace, is a likely place for water to get stuck, too! But, for now, we assume you started looking for us because your leaky damper is letting your inside air out. A leaky damper is the main reason for higher energy costs than you ought to be absorbing.
Sometimes called “flappers”, and quite rightly in many cases, chimney dampers are usually closed for the non-heating seasons. The ones in fireplace throats are “flaps” that open and close to function in the same way that the epiglottis does in our own. They are made from metal to withstand heat, and – when new – they form a tight seal when closed.
That prevents both inside-air loss and penetration of your firebox by water, — as important as keeping water out of your lungs. If you have closed your throat damper and, right now, you feel cold air coming into your fireplace, the damper is probably shot. This happens naturally over the course of time because water comes into contact with metal and it rusts.
That accounts for half of the thinking behind – not flappers – top-mounted dampers and ‘chimney balloons’. Once you know your throat flapper is ‘worthless’ because it leaks, it is extremely difficult to do anything about it because of where it is. That accounts for the other half of the thinking and the best answer is often the addition of a top-mounted damper.
For roughly half the year, top-mounted dampers function as “chimney caps” as well. They tightly seal your chimney at the top, where all the trouble begins, and the flapper in the throat is permanently locked open. They may not be the best solution for you, because they obviously cannot be closed – and neither can flappers – during fireplace use. Whatever you end up deciding, it is a major change to your fireplace system, so involve your certified chimney sweep early. If you are fast enough, you might not have to face these choices!