Hello!
The air inside the building is easily pressed out the windows because the air is composed of widely spaced molecules in the gas phase.
The word "gas" was created by the Netherlandish scientist Jean Baptista van Helmont from the Latin word "chaos". The gas phase consists of molecules with high kinetic energy, that adopt the shape of the container and tend to expand. The molecules are essentially free, and the gravitational pull on them is negligible.
Have a nice day!