[August update] Just wanted to add that all my windows have "micro-ventilation" - either by design or simply because they are old and have gaps. So essentially, there is always some air coming in or out in the bedrooms.
So - do I really need those air vents in my bedrooms? Aren't they just a legacy and no longer needed? Please help. Thanks
[End of August update]
My 1950s house has air vents in some bedrooms. They are literally holes in the wall with a plastic grill on both ends.
I like to regularly ventilate my rooms simply by opening windows. The heating is via a gas boiler downstairs. Yes, there is a log burner in the main living room downstairs, but I use it once in a blue moon.
I would like to completely block off this air vent - basically to fill it in with the expanding foam, plaster and paint over.
The only question - can I safely do it? Any reasons why not to?