"DOWNDRAFT" & "SMOKEBACK" PROBLEMS
One common cause of downdrafts is the close proximity of tall trees or tall buildings. These present an obstruction to local airflow and can cause eddies and vorticies in the vicinity of the affected chimney. Not only can wind blow down the chimney, it can also increase local air pressure at the pot relative to the ground floor of the house, this can cause chimney draw to stall or reverse direction, sending smoke into the house! These effects are wind speed and direction dependant.
Tall trees creating downdraft Tall/close buildings causing downdraft
The aerodynamics of airflow over and around buildings is very complicated and unpredictable. Variable wind direction and intensity, local topography, vegetation, buildings and even your own house/roof/chimney design all play a part. The vast majority of houses don't suffer significant downdraft problems. The occaisonal, random puff of smoke from a fireplace during high winds is fairly normal but if it occurs regularly you may benefit from having a cowl fitted. If the problem appears to get worse and "smoke back" occurs even during light or no wind conditions your chimney most likely needs sweeping! We would never recommend fitting a cowl unless there is clear evidence that any "smoke back" is being caused by downdraft. We will always visually inspect the house, roof and nearby possible causes before even mentioning fitting a cowl.
In a lot of cases where "smoke back" is reported by the homeowner a thorough cleaning of the chimney solves the problem!!
If you suspect you have a problem call us to discuss it and your options.
Having your chimney swept regularly reduces the chances of smokeback and maintains optimum flue efficency!
Another common problem reported to us by customers is that a fire is "difficult to light" and smoke spills from the fireplace when the fire is first lit. The problem abates after the fire has been going for a while.
The cause of this is three-fold:
First of all, when you light the fire the chimney/flue is cold and it is much harder for combustion gases (smoke) to rise due to dilution in the cold air in the chimney. The principle of flue draft and draw requires the flue gases to be warmer (and hence lighter) than the surrounding air. Once the fire gets going and the air in the chimney is warm a proper chimney draft is set up and air is drawn into the fire from below. This is a self sustaining process. To aid the starting of the fire and initiate a proper chimney draft try burning several sheets of newspaper on top of the fire you have set. This will send hot air up the chimney and help initiate a proper "draw".
The second cause can be due to local weather. Sometimes a phenominon called "spring and autumn syndrome" occurs whereby the outside temperature rises whilst the inside of a building remains colder. (very common here in Scotland and is exacerbated by sturdy brick or stone building construction!). This causes air to sink down the chimney (hot air rises but cold air sinks!) making lighting the fire difficult as described above. A sign that this is occuring is the smell of "soot" issuing from the fireplace or in the room where the fireplace is. To overcome this problem the flue needs to be warmed up before a proper draw can be initiated (see above).
The third cause which can occur on it's own or in combination with the previous mentioned problems is a dirty chimney/flue. A dirty chimney not only has a narrower channel for flue gases to escape through, it also offers a rough surface over which the flue gases must pass, this causes considerable resistance to the gases. A dirty chimney is inefficient at removing combustion gases and makes initiating a proper draw on the fire difficult. It is also at high risk of a chimney fire!
The best way to reduce the effects mentioned above is to have your chimney swept regularly!
Another very common problem occurs when someone moves into a new house and lights the fire for the first time. Smoke billows out of the fireplace and very little (if any) draw can be started. The fireplace is useless!
Cause: Believe it or not most often the chimney has been capped off and is "disused"!
Estate agents are very keen to highlight that a house has an "open fire" but this does NOT mean that it is useable and/or safe to do so!! Several customers recently have been caught out by this and the only option to be able to use the fire is to have the pot capper removed and the chimney swept, see our PRICES for more details. One customer told us that the survey they had done on the house highlighted the fact that the chimney stack had lichen growing on it, however the surveyor failed to report that the chimney had been capped off!!
Be aware of capped off chimneys when moving into a new house!If in doubt call us and we'd be happy to come round and check for you.
Below is a photo of two capped chimney pots.
Do NOT use your fire if your chimney has these!
SMOKE IN THE HOUSE
Another fairly common problem, especially in old houses is the smell of smoke somewhere in the house, usually in an upstairs bedroom. The problem may be more apparent when a fire has recently been lit or will seem worse after the chimney has been swept. THIS IS A SAFETY ISSUE DO NOT IGNORE IT!!
The problem here is that over time the integrity of the maisonry and mortar of the chimney has become compromised due to age/corrosion. Put simply, flue gases (smoke and fumes) are escaping from the chimney into the house.
This presents a very real danger of carbon monoxide poisoning and is a fire hazard!!
A smoke test may prove that gases are escaping from the chimney but if you have this problem your nose will probably have already confirmed this!! The only real option here is to have the chimney relined by a builder or specialist chimney engineer. The usual method (and cheapest) is to have a metal flue liner fitted. The builder/engineer may well carry out a CCTV survey of the inside of the chimney prior to quoting for the work. Mamore Chimney Sweeping doesn't currently have the capability to do this but we hope to offer it in the near future.
Remember: If in doubt get it checked out