In Sept we moved into a new house (built in the 1920's, we think). We had the chimney swept and we've been successfully using the open fireplace ever since. But on a couple of evenings smoke has blown back into the room which is pretty unpleasant. Tonight this has been really grim - big sooty wafts billowing in. We've had to move into another part of the house.
The chimney is in OK condition as far as we can tell. The house is not on a particularly exposed spot.
What can we do???
GF
We've had to move into another
By some rods and do it yourself.
I don't trust chimney sweeps after my dealings with them.
When I did it myself after there attempt, I got loads of crap out of the chimney. All they did was to punch a hole through the middle of the crap
We get the whole 'room full of smoke' thing when lighting our open fire if the air pressure is high (such as during the still, foggy weather before Christmas). I always make sure to test whether the chimney will draw by holding a lighter flame inside the top of the fireplace. If the flame is blown downwards, I torch a sheet or two of newspaper held just in the bottom of the chimney to send some warm air up (making it draw upwards), then light the fire lighter and small sticks. It just has a plain chimney pot on top - that doesn't get afftected much by the wind once the fire is lit. Chimney pot design?
Buy a cowl
Sounds like good advice - but don't really know what you mean. Are there different kinds of cowl? How do I decide which kind is best? Will this solve the problem for sure?
G
What's the weather like where you are? Been a bit blowy up here, gusts to mid 50's mph but settled down now with only a 30mph mean wind speed (F7 Near Gale). It might be the affect of a particular strength wind, from a particular direction, with certain doors open.
Our open fire will smoke out of it's exterior piped air vent under some conditions (particularly affected by which doors are open) and just occasionally the chimney will give a puff of smoke but that is normally only just after lighting it before there is any heat in the fire.
EricP explained on 29/12/2006 :
rotated to always face away from the wind. I have no idea how effective they were - possibly not so good in less windy conditions where the wind was unable to turn them to face down wind.
Our blow-back problem was solved permanently with the fitting of a Colt Cowl. Got it in Gibbs & Dandy, fitted it myself. Must have been up there about 11 years, now.
There are many reasons for blowback. Is your chimney situated above your roof ridge? It should be, if not, adverse pressure effects and turbulence can cause trouble.
Your fire opening should be about 5-6 times the area of the flue throat otherwise problems can occur. Fireplace surrounds that are poorly designed can also exacerbate problems ( an arched surround that is too high for instance ).
Another problem can occur when the wind blows from a particular direction and creates low pressure on the side of the house the room that the fire is in: having a leaky window or vent on that side can conspire to suck smoke into the room.
Best to start with a cowl to deflect downdrafts: if your chimney is in the lee of some tall turbulence causing obstacle or if it is below the ridgeline of your roof that may be the only solution.
Andy.
I had a similar problem with wind gusts, which was finally fixed with the fourth design of cowl, which used the Venturi effect. This was like two large horizontal stainless steel saucers facing each other with a small gap between them. The total area of the gap should be the same cross-section as the chimney flue. There's a hole in the middle of the lower saucer where it's attached to the chimney. The cowls that didn't work as well were the Vacu-Stac and another two non-Venturi types. I didn't want to use movable or spinning cowls to avoid maintenance in a remote area.
Smoke will not exit the chimney, and will blow back, if the air at the chimney's top is warmer than that at the bottom. You'll have this situation if you're trying to start the fire in the afternoon or evening of a day when the outside air warmed the top of the chimney more than the air at the bottom-- in stone houses this is almost always the case. If you start the fire in the morning, this won't happen. To get a fire going later in the day without chimney blowback, you can (must) first the chase the warm air at the top of the chimney by torching a newspaper at its very base.
Very interesting, but I don't think this is our problem because the smoke mostly goes up the chimney - but (some evenings) every few minutes it blasts in for a few seconds.
Other suggestions about turbulent airflow over the chimney and about wind gusts creating lower pressure (and drawing air down the chimney and out of the room through badly sealed windows and doors) seem consistent with our problem.
The solution seems to be a cowl and the choice appears to be between the ones that look like spinning cheesegraters and ones that look like top hats.
That seems to be where I am.
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