Chimney Breast Ventilation Question.

[derekpara]

Situation : 1930s semi. Original fireplace removed and opening bricked and
plastered. Corresponding chimney pot capped with vented cap.

Question: Is a vent necessary/advisable in the bricked up fireplace ?

Cheers.

D

[KARL]

If you want a draughty room then fit ventilation to the fireplace. If you want the best way to seal off the archaic feature then fill the pipe with expanding foam, at least from top and down into the wall as far as reaching heated areas of the building. The ultimate is to remove the external chimney structure altogether (top bit that sticks up) and complete the roof to leave no trace of its existence. The current arrangement can, under adverse circumstances, cool down the wall where the fireplace was and, at very worst, therefore cause some build up of dampness on/in that part.

[The Builder]

Derek, you don't say whether the chimney breast is on the internal, separating wall against next door, or on the gable end.

If it's internal, then this wall is unlikely to become cold. It's often advisable to provide "through-flow" ventilation with a sealed off fireplace, but in this case, I don't think it's terribly important.

A different story for an outside wall. This wall will become a cold surface. As an alternative to Karl's foam, temporarily removing the pot and pouring "Vermiculite" insulation beads would be a lot easier.

If you don't want to go to that trouble, fit a vent on the OUTSIDE of the wall by drilling though into the flue near ground level. This will adequately vent the flue without causing an internal draught.

[derekpara]

Thank you both for your answers.

Builder, the chimney breast is on an internal, separating wall against next door. I don't have the means, practical or financial, to fill the cavity so I assume that a ventilator is not absolutely essential.

[The Builder]

Yes, a 1930s semi is likely to be cavity wall construction on the three other walls. A flue void is really similar to having a cavity between the houses.

Cavities are sealed, and not vented. Nothing to worry about.

[derekpara]

Cheers, B.

Derek