The correct choice of chimney cowl can make a big difference to the performance of your new wood burning stove, yet this installation accessory is often overlooked. There are too many varieties of chimney cowls and terminals for me to cover in a single post, so I am going to focus on the types most commonly used with wood and multi fuel stoves. The cowls I am looking at are designed to be attached to a chimney pot, usually with strap or bolt fittings, but similar equivalents are available for use with flexible chimney liners or twinwall flue systems.
Bird Guard Chimney Cowls
If you have no other chimney cowl at all, I would recommend you install a bird guard. You would be surprised how many people come down to breakfast to find strange scratching noises coming from within their woodburner, to discover a distressed bird which has found its way down the chimney and become trapped in the stove! More importantly, you want to prevent birds from nesting within your chimney as this could result in the flue becoming blocked. Bird guards can be made from either wire or mesh, and will self-adjust to fit your chimney pot.
Rain Cap Chimney Cowls
Rain cap cowls are very straightforward, simply shielding the chimney opening to prevent rain running down the chimney cavity. Rain in the chimney isn’t normally a big issue during the colder months when a multi fuel stove is in regular use – the heat from the stove will simply cause it to evaporate. However at times when the stove isn’t used water can pool within the flue system or even find its way into the stove where it can cause rust problems. Rain caps are available with or without mesh sides to keep out birds.
Anti-downdraught Chimney Cowls
Anti-downdraught cowls are useful in areas where high winds often force smoke back down the chimney – as well as it being unpleasant to have smoke coming back into the room, downdraughts increase the risk of exposure to carbon monoxide in your living room. Anti-downdraught cowls generally incorporate a bird guard as well.
All-Purpose Chimney Cowls
All-purpose cowls combine the properties of several different types of chimney cowl to give some protection against downdrafts as well as keeping out rain and birds. As the name suggests, they are a general-purpose product rather than a remedial cowl – people with severe downdraught problems may be better off with a more specialised cowl.
Revolving Chimney Cowls
Rotating cowls are expensive, so sometimes people think they must be the best on the market. In fact rotating cowls were developed as a remedy for weak flue draught – as the fins rotate air is pulled up through the chimney. You should never fit a rotating cowl to a chimney that is drawing normally as this could cause your stove to overfire and become damaged. Rotating cowls are often seen in urban areas where close proximity of other buildings affects air pressure around the chimney terminal.
Problems with flue draught are not always evident at the time the stove is installed, as they can vary according to weather conditions. Unless there is reason to believe you have a chimney problem StovesAreUs recommend use of a general-purpose chimney cowl – remember you can always install a different cowl at a later date should the need arise.