Ventilating chimney breast

TheCyclingProgrammer

We have removed the hearth and gas fire from our lounge and are currently left with the opening.

The TV is mounted on the chimney breast and the plan is to construct a false stud and plasterboard wall around the real chimney breast to conceal wiring etc.

The question is what to do about the chimney opening. It won't be visible once the false wall is built but is it worth blocking it up anyway? It doesn't need to look nice so I assume I could just stick a piece of hardboard over it?

And what to do about ventilation? I assume if I cover the gap up, I will need to cut a hole in the hard board and then a hole in the plasterboard false wall too, and fit an air vent over the hole? Would I need to link the two holes with some ducting to ensure the air goes up the chimney or is this not necessary? Presumably if the hole in the real chimney breast is left open then just a vented hole in the false wall should be sufficient?

Finally, what about reducing drafts and wind noise? Should we have a certain type of cowl fitted to the pots? What about stuffing a chimney balloon or home made equivalent (bin bag stuffed with paper) inside the flue? We have put one in there today to try and reduce wind noise - is it safe to leave in there permanently when the chimney breast is covered up? Maybe with a piece of pipe to ensure it can still be ventilated?

muckybutt

As an ex sweep myself - start by getting the chimney thoroughly swept to get rid of as much soot and tar as you can.

Chimneys and houses require ventilating at all times to allow moist air out and fresh air in. What I would recommend is block the chimney opening off with a sheet of hard board or ply wood, cut a hole in that towards the top of the opening, that way should debris fall down over the years it wont block the vent up. Always worth stretching an old pair of tights across the vent as well to stop any insects coming through.

On the studded wall you will also need a vent to keep the air moving, personally I would insulate between the stud and chimney breast with rockwool, leaving a gap for the air to circulate through.

Chimney pot / s should ideally be capped off as well with a breather vent cap, they don't want capping off air tight as some do !

TheCyclingProgrammer

Thanks for the reply. What is the benefit of having the chimney swept?

I must admit I considered insulating between the studs and the chimney breast but I wasn't sure what it would achieve. Maybe a small amount of sound isolation? Would this reduce the chance of condensation or damp?

Good tips about leaving a hole at the top of the hardboard and covering to keep out insects. Don't want them flying around inside the wall!

I don't want to have the visible vent too high up - would a foot from the floor, but lower than the hole in the hard board be sufficient?

TheCyclingProgrammer

Oh, and is it safe to leave our home made chimney balloon blocking the flue with a small gap for ventilation or would this cause a problem? I'd leave a note inside the chimney in case somebody opens it up in the future.

What would be a reasonable cost to have the chimney swept and a vented cowl fitted on the 4 pots?