Blocking up a redundant flue.. how? with what?

RainbowsInTheSpray

Hi everyone. I've had an old gas fire in my living room disconnected and removed, revealing a one foot square opening in the wall and a narrow vent type of flue leading upwards from that.

I won't need this opening/flue any more as I am getting out of fossil fuel and will be replacing the gas fire with a stove-lookalike electric, fan heater thing. I have a cut-to-size piece of 1cm aquapanel ready to mortar into the front of the square hole... but I assume I should be putting something in the void behind to block it and stop downward ingress of cold air from the outside. Can anyone advise me as to what to use here? I was thinking of just loose laying of house bricks and maybe a bit of glass fibre insulation stuff.

Any thoughts very welcome.

Doozergirl

You actually need to vent it, not block it.  You want an air brick, of sorts, at the bottom, and a cowl on the top of the chimney that still lets air through.   Older houses need to breathe.  

You need airflow top and bottom to keep it dry.   Block it up and you will end up with damp.  

RainbowsInTheSpray

Vent what? The gas combustion fumes are history.Thanks but the house is only 40 years old and has air bricks aplenty elsewhere. I don't want an unnecessarily cold wall right behind where a fire will be located. This strikes me as perverse in the extreme.