Sensing open Windows

HI ,

I’m looking to create a setup that alert me if any of the windows in my house have been left open.

I don want to run contact sensors to each window and was thinking that a holistic approach to the pressure in each room might be the way to go.

Is there a sensor setup that could be used to achieve such a detection

A BMP085 will detect very small changes is pressure. (so in theory this should be possible) There will be a problem as turbuence will affect readings from outdoor sensor. I dont believe this is the smartest approach. My idea would be wires and micro reedswitces/magnets