Sat, 02 May 2026 09:59:51 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18014&Focus=304175#Comment_304175 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18014&Focus=304175#Comment_304175 Mon, 06 Nov 2023 16:34:14 +0000 tony
Many of us have heard of ‘sick building syndrome’. I am going to talk in this short article about something I’m going to call ‘sick chimney syndrome’. This problem occurs when a chimney is subject to cold conditions at the same time as it gets wet either from saturation or from moisture rising from the house and condensing in the cold part of the chimney above the roof. The upshot of this is that we get a cold tropical rainforest scenario developing in the flue caused by moisture in the house being drawn up the flue by a process of diffusion without the necessity of any air movement. Moisture diffuses through the air and condenses in the brickwork of the chimney or on the capping, add my, on occasions, drip down the flue. Once this process is started, it’s almost impossible to stop it as the evaporation that will occur from the brickwork of the chimney, causes it to be colder than other places nearby, and then that in turn causes further condensation. I call this ‘pumping’ and it is where moisture from the house is literally pumped through structure and into the flue and it then condenses in the brickwork. Moisture moves through the air in a similar way to water in a pipe but no air movement is necessary for the process I am describing.

The result is that the chimney is perpetually wet and doesn’t ever dry out. My recommended solution to this problem is to ventilate the chimney immediately below the capping with two air bricks for each flue on opposite sides of the chimney, so there is a through-draft immediately underneath the chimney capping. Then it is also necessary to ventilate lower down the chimney either in the loft by removing a brick from each flue or immediately above the roofline, one brick per flue should be sufficient.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18014&Focus=304176#Comment_304176 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18014&Focus=304176#Comment_304176 Mon, 06 Nov 2023 17:04:56 +0000 djh ]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18014&Focus=304178#Comment_304178 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=18014&Focus=304178#Comment_304178 Tue, 07 Nov 2023 08:46:41 +0000 kristeva Posted By: tonySick chimneys syndrome

Many of us have heard of ‘sick building syndrome’. I am going to talk in this short article about something I’m going to call ‘sick chimney syndrome’. This problem occurs when a chimney is subject to cold conditions at the same time as it gets wet either from saturation or from moisture rising from the house and condensing in the cold part of the chimney above the roof. The upshot of this is that we get a cold tropical rainforest scenario developing in the flue caused by moisture in the house being drawn up the flue by a process of diffusion without the necessity of any air movement. Moisture diffuses through the air and condenses in the brickwork of the chimney or on the capping, add my, on occasions, drip down the flue. Once this process is started, it’s almost impossible to stop it as the evaporation that will occur from the brickwork of the chimney, causes it to be colder than other places nearby, and then that in turn causes further condensation. I call this ‘pumping’ and it is where moisture from the house is literally pumped through structure and into the flue and it then condenses in the brickwork. Moisture moves through the air in a similar way to water in a pipe but no air movement is necessary for the process I am describing.

The result is that the chimney is perpetually wet and doesn’t ever dry out. My recommended solution to this problem is to ventilate the chimney immediately below the capping with two air bricks for each flue on opposite sides of the chimney, so there is a through-draft immediately underneath the chimney capping. Then it is also necessary to ventilate lower down the chimney either in the loft by removing a brick from each flue or immediately above the roofline, one brick per flue should be sufficient.

Very interesting Tony.

I have a rather unimpressive old, stack on one side of my house which is 'sick', although perhaps not for the same reasons. Amongst other issues, there's a leak in one corner which occurs intermittently despite concerted efforts by the previous owners to fix. I've had 3 roofers up there and none could find an obvious issue. I suspect the bricks are unable to dry out properly after considerable bouts of rain, maybe due to a concrete repoint. But I also suspect there is a major leak somewhere in that corner. I plan to remove it completely down to loft level, whilst installing a wood burner. The extra cost of a meter of twin wall flue liner is a small price to pay for a hassle free roof.]]>