There is no difference between the air pressure inside or outside the
home. The only time it will change and only for a second is when you
slam a door or open a door quickly creating a vacuum or high pressure
cell.

If you are in a building - like the Empire State building - and go up
the elevator with a barometer. It will read lower as you go up because
it is always measuring the weight of the air in the atmosphere "above"
its location. A barometer can be used as an altimeter if it is
calibrated for feet instead of air pressure in inches of mercury.

Barometer are one of the best instruments for predicting the weather. If
AP rises - the weather will be dryer and nicer. If the AP falls - you
are going to have wetter and worse weather. If it goes down super fast -
watch out for tornado or hurricane :-)

Of course you "need" a barometer. Put in a place where you have good
light to read it.

Harry