Wall vents are so passé.
*They are essential in rooms that have an un-flued gas heater or open fire, and in hot and steamy areas (bathroom, laundry and kitchen) to allow good ventilation but are just drafty holes in all other rooms.
If you are using energy to heat or cool your house it is a good idea to draught-proof these vents to stop the precious air escaping. This GIY job is a good temporary solution.
If you want some fresh air you have to take control of it - windows that open and close are great. Permanent wall-vents are bad (except *).
Trickiness Rating: EASY