Chimney ventilation

[Nigel T]

Hopefully and easy solve.

My house has just been re-roofed and I asked that the two un-used chimneys (one on gf and another on ff) were demolished below the roofline and tiled over (they are on an internal party wall as its terraced).

Will condensation still be an issue and do I need to install an air brick where the old removed hearths were?

Thanks for your input.

[MarkyG82]

I'm interested in this for a slightly different reason.  Planning on capping the chimney to seal it to the elements and maybe even use it as a conduit for ventilation ducting.  At what point (vertically) should I add a further barrier?  You have chopped yours off.  Did you seal the top in any way?  I'm thinking of one of those inflatable jobs but nearer the top (accessed via loft space) so the cold region is limited to above the living spaces.  I'm probably nuts!!