Is it at all sensible to fill in this vent? Maybe with expanding foam or similar?
This is a 23cm by 23 cm vent in the cupboard in the corner of my kitchen, it goes through the entire wall, and it is covered by a thin plastic vent on the outer wall, it makes the whole room freezing. I live in a 1960s build 3rd-floor apartment with central heating, what is the need for such a gaping hole in the wall? I only just discovered it, it was completely taped up and had been for at least 6 years.