Object Instances

Hi, I’m very new with swift 3d.
I want to create a small animation that involve various buildings. Each building will have several windows but I have noticed that each window count as an object then when I export the animation to flash I have a huge animation of almost 2MB.

I think there must be a way where you can say that it’s just one object but many instances of it to reduce the file size?

Can someone help me?

Thanks,

Juliana Castillo