Wow, I never thought a house could be that air tight!
New construction homes here are that tight. Too tight if you ask me. Unhealthy air too tight. A house needs to breathe alittle. They seal every little opening as the home is being built. The holes the electrcian drills to pass wires through sills, walls etc all get a shot of expanding foam.
My house is 60 years old and even with efforts to make it more sealed, it still has lots of opportunities to breathe. I have a 4" pvc pipe through the band joist in the room with my boiler to bring in combustion air. Your home doesn't like a vacuum. If you are exhausting air outside, it's got to made up somehow. Better to manage it by purposely bringing it in where you need it rather than through every bath and kitchen fan, around windows and doors, etc.