My house is a 1930s built semi. All upstairs rooms have a vent built into the wall just below ceiling level.
I know I need air bricks at floor level but what is the use of these at eaves level? Don't they just allow heat to escape? A cold draught comes through one of them. If I want ventilation can't I just open the window?
The house would originally have had open fires downstairs - were they installed because of this? It now has a gas boiler with its own flue.
Am I able to block the vents in some way or would that be a silly thing to do?