Chimney question

[Tonythecat]

Hi I'm in the process of preparing my fireplace for an inset wood burner. The builders opening is currently open (see pic) and obviously letting lots of warm air to rise up the stack. During the last couple of cold nights I have had some condensation forming towards the top of the stack and dripping down into the builders opening so I'm thinking this is probably due to the fact that a lot of moist air is going up and condensing in the colder upper faces of the stack. My worry/concern is that when my stove is fitted I will essentially be blocking off both ends of the stack as the stove will block the bottom and the cowl (liner hanger type) will block the top. I understand that this will reduce warm air flowing up the chimney from inside the house and the coal prevent the stack becoming quite so cold but it will also result in a lot less air movement within the stack so although I'm hoping that the issue may improve I'm also concerned that it may become worse. Any advice would be very welcome indeed thanks in advance

 

[blup]

You need specialist advice, chimney sweeps are often (always?) qualified to give that and even sign off flues as safe. I would guess that the heat from the wood burner should more than adequately deal with condensation from the heat generated within and from the burner/flue liner. But as said you need a specialist to look at the chimney in situ.