I have air bricks to the front and rear of my property just below the level of the dpc, at the front they are in a solid wall , at the back i have one each end of a sliding double glazed exterior wood door approx 2.5 mtrs wide, the floors of the house appear solid with 1" chipboard laid in some way above, unsure of this bit cause i dont really want to rip it all up . my question is what are the vents for and what would happen if a dozy builder blocked them in with a solid floor when building a extension