Open fire ventilation / draw

[Estrella]

Hi ,
I have a small open fire in a small sitting room - 13ft square .

When their is little wind outside the smoke when initially lighting the fire comes back in the room. If i open a window the smoke screams up the chimney at a great rate of knots and the problem is cured. Other than the fact any heat whilst the fire is lit is lost as the window is open

Once the fire is established the window can be shut without any detrimental effects.

There are two air bricks which sit beneath the wooden suspended floor. presumably to stop the suspended floor rotting. There are no other air bricks in the room.

The house was built in the mid 1800's and has always had this layout as far as I am aware , so is it a case of additional ventilation required or a chimney that can shift more smoke ?

EDIT: the chimney is swept regularly.[/b]

 

[Symptoms]

Cleva - does it happen everytime you light-up or just when it's a little windy. Sometimes weather patterns can affect the behaviour of chimneys - the most common one being an Occluded Front where the surface of the cold front catches up with the warm front, and the warm air is lifted off the surface. Basically, the air pressure above the chimney is higher than below preventing the smoke from exhausting, but once the fire is blazing the hot gases drive up the chimney taking any smoke with them.

You say you can minimise the smoke effect by opening a window, what happens if you open the room door (keeping the window closed)? Victorian houses always were leaky (draughty) so venting was usually not a problem ... then we swapped the rattling sash windows for 'hermetically' sealed PVC jobbies & draught excluded the doors and then wonder why the fires don't 'draw' anymore. Have you got placka windows & doors?

 

[Estrella]

Ahh some good questions there Symptoms.

The smoke doesn't always come into the room , but it is a fairly regular occurrence. Opening the internal door does help.

The front elevation (the room in question is at the front) has UPVC windows.

You are correct when you say the fire is fine when it is raging, never had an issue when it is established.

The only true constant is that when it is raining the smoke always comes back into the room until the fire is raging. I put this down to the fact that there was no cowl on top of the chimney

The other reason for the questions are that I am considering having a multi fuel stove put in its place so I was wondering if additional venting would be required.

Thanks for your info , most interesting

 

[Symptoms]

Cleva - a cowl might help. When I moved into my place one of the open coal fires smoked so I fitted a cowl ... fantastic improvement. When I converted to gas/coal effect I took the cowl off 'cos it wasn't required anymore. It was a square, galvanised job that clamped on the inside of the pot ... I don't think they're available any more, but I'm sure a supplier will advise you about something suitable..

 

[Symptoms]

Cleva - I just found the old installation note for that cowl I fitted, it was a Colt Cowl - Universal Type, made from non-corroding alloy.