Anti Down Draught Cowl

I had the same problem with my coal effect gas fire in addition to having fumes come ino the room when we used the fire. Unfortunately I have a galvanised flue instead of a proper brick chimney. I ended up calling the fire manufacturer who told me to get an Aspiromatic rotating cowl.

On another note the cowl is virtually silent until it gets very windy and then it rattles so much it keeps us awake at night. Not sure if it's the wind being too fast for the cowl to cope with or it's the flue rattling around due to the load.

There's a dense column of cold air in the chimney, the house is warmer than outside and has vents to the outside. The flue exit is low down in the room so a thermosyphon exists, allowing the cold dense air in the chimney to push warm (often moist) less dense air out of gaps in the house fabric at a higher level.

The rotating cowls only have an effect if it's gusts of wind causing high pressure in the chimney, not a draught caused by static pressure differences.

AJH

I think I recall an idea of putting a (special) balloon in the flue - to stop a down draught. If you lit the fire it would burst so there was a safety aspect in the concept.

Notice during the recent cold weather that

It's not possible to use these ballons when the exhaust vents for some coal effect gas fires consist of four or five square holes 3x3cm in size like ours does.

It seems there's a gap in the market (no pun intended!) here.

Check with the manufacturers of the gas fire what terminals are suitable.