Air brick too big

[tostaky]

Hello, we’ve converted the loft and now i am using the box room as my WFH office (1st floor, front of the house)
except there is tbis massive air brick which makes the room super cold. I can feel the cold air flowing as i am sitting in my office typing this message.
it doesnt even look like an air brick, more like a hole in the wall and two metal plates. See picture
how do i make my office warmer? I could use an extra eletric heater but the warm air will just get out. It is a very small box room.
i understand air bricks are important. But maybe i could update them with something more energy efficient?
TIA

Is this a proper box room with no window or a small bedroom? If no window you will need some sort of ventilation and this is it. If you don't need ventilation and can work with the door open you could tape cardboard over it temporarily. Longer term you could fit an opening/closing vent.

You can get plastic grilles to put over the front of them. Possibly with adjustable open/close levers.

Thanks for this. There is a drafty single glased window in the room.
i will look into thise plastic grilles. If not cardboard during winter. Thanks

You can scrunch up newspaper and fill the cavity, assuming you can get the inside grille off. It keeps the airflow but stops the draft. And I'd also fit a bit of insect mesh inside while you are at it.

These are quite common in older houses. You can get plastic covers/grilles that you can open and close.