Some 80% of chimneys don’t have chimney cowls and most appliances will run with an open Chimney Pot, however as a registered HETAS installer, I would always recommend the fitting of a chimney cowl, especially if you are going to have a gas fire or wood burning stove installed, So read on to find out why and which chimney cowl to choose.
Chimney Flue Liner
For a gas fire or wood burning stove installation, these usually require a flue liner and I would strongly advice you fit a Cowl (suspended/pot hanger type). You have to consider that your flue liner is basically a metal pipe running from you chimney pot all the way down to your appliance, without a cowl it would allow rainwater to run straight down your chimney and into your gas or solid fuel appliance.
With a non-lined brick chimney any water that enters normally dries out from the air that is pulled from the bottom, therefore eliminating the risk of damaging your appliance and has little effect on your chimney itself, So always factor in a Cowl when considering Chimney lining cost
To Prevent Blockages
Usually caused by birds either nesting in your chimney or falling down the chimney and getting stuck in the liner. This is very dangerous with wood/solid fuel fires and especially so with gas fires, as it can result in carbon monoxide/dioxide poisoning for the inhabitants
To Prevent Down Draughts
Down draughts are caused by a few factors the common ones are,
- If your house or chimney has a taller building next to it
- If you have tall trees next to your property
- If your property is located in the bottom of a valley.
The problem is usually intermittent and would occur in windy conditions or a gust of wind from a certain direction blows down your chimney and you end up with a room full of fumes.
This problem can be eliminated by fitting an Anti Down Draught Cowl. They act in a similar way to an aircraft wing, which creates an updraft, the cowl sits on top of the chimney pot and pulls the fumes upwards.
These act like a fan drawing or sucking the fumes up the chimney/flue liner using wind power, if you have a day without wind, obviously the effect is greatly reduced. My view on this type of cowl is that they are a bit gimmicky and rather expensive.
Static Cowls – These come in two forms:
also called an anti down draught cowl with pot hanger. This type of Cowl incorporates a clamp to secure your chimney liner to your chimney pot and hence stop your liner falling back down your chimney
If you don’t have a chimney pot – Just a standard Anti Down Draft Cowl will suffice, make sure they come with a plate to fix the the liner to it. You can also fit these types of Cowls to chimneys with pots, it is then just a case of removing the pot to fit the plate and then replacing the pot.
Obviously it’s better to get the Suspended Anti Down Draft Cowl and leave you chimney pot in place plus it will reduce labour charges.