The vent regulations over here often lead to them being intentionally blocked due to that fear of draughts!
They require a vent in the outer wall of every room at ceiling height. Sometimes these are louvers types, sometimes they're a panel with an opening at top. These can be partially painted / papered over and are less visible.
They're almost always replaced with hit and miss slid to open/close louvers.
There's also a requirement for vents under the floors (radon / other nasty gas accumulation prevention measures)
Some places also have vents BETWEEN the rooms and the hallways to allow for maximum circulation! Without exception those are blocked up!
There's a major risk though that you can just cut off all the oxygen to your home and end up with sick building syndrome if you take some of those environmentally friendly measure too far.
They SHOULD require a centralised ventalation system that contains a heat-exchanger. Ventaxia do a nice one. You can vent the house really effectively and still retain the heat.