Thinking about cowls
Moving around the country, we see so many different chimney terminations. The bit that finishes the job, the cowl, that can be the most vital last link in the chain. So since working in the stove industry my eyes are drawn to the tops of buildings. I love seeing people maintaining a pot and cowl combination that’s been around for years and is sympathetic to the building. I also really love a clean modern finish with a smart round pot and stainless steel cowl that’s well fitted and serves the installation.
We’ve been fitting cowls for some years and have had some hairy experiences. To start with, a stainless steel cowl was extremely pricey so we had to find a cheaper option. That didn’t last long! Even the more expensive ones can have faults though; we had a run from a reputable supplier where the rivets holding the ‘lid’ on weren’t the same quality and they literally flipped the top off after one or two season’s use. For the past few years we’ve gone to Midtec stainless cowls. They do the job well.
The cowl protects the flue from the elements, including ingress from water or debris. But the primary function is to vent the flue, letting the stove draw a good air supply to feed the fire. Most importantly, all the noxious gases pass through quickly. There’s a misconception about mesh in a cowl. Solid fuel appliances can have meshed cowls, at the right size. Gas cowls use a smaller gauge mesh and are simply dangerous when used on a stove installation.
As seen in these pictures, residue is life threatening. This is caused by the customer’s choice of fuel. Wet or treated wood or poorly sourced smokeless nuggets leave a residue, and cause a blockage. Don’t blame the sweep. This kind of tar like substance won’t be shifted by a sweep. The sweep’s brush should be able to spin around inside a securely fitted cowl and not dislodge it. Many customers try and tell me that the sweep knocked it off, but if the cowl doesn’t allow for sweeping, it’s not correctly fitted.
Birds are a hazard to our chimneys but this fix to the problem could have been serious. Luckily the homeowner had a co alarm and were able to call us to help. Scary isn’t it?
The key is making sure you have the right cowl for the job. Don’t go fancy. Keep it simple. What does the cowl need to do? Protect from the elements, and birds? Avoid down draft? Assist with draw? All of the above? Get a chimney expert to make sure your cowl does the job.