Not thing to worry about the fresh air, there is no any house are 100 % "Air Tight", Whenever, outside averment have low wind or strong wind, the air in the house also will be carried away this called "Air Drift", so the air in the house will not be as "old" as you think.
Go around your house, check to see there is always a "hole" at the bottom of the Brick, which is helping the "Air Drift" even it is not design for it, actually the "hole" is for moistures can be escape from house, it doesn’t fezzes up in winter
Go around your house, check to see there is always a "hole" at the bottom of the Brick, which is helping the "Air Drift" even it is not design for it, actually the "hole" is for moistures can be escape from house, it doesn’t fezzes up in winter