Exterior scenes need time to be planned if you want to minimize any issues and have a smooth workflow. Although you may be working with small buildings in some situations, you still need to plan ahead how to build the scene.

One of the first things you have to check is whether the client wants a still image or an animation. Why? For one, with a still image, you don't have to worry too much about what is behind the camera and you may only have to add some geometry to be reflected on the windows. However, when working with an animation, the camera may move to a position where you need to add some objects; otherwise, it will be just an empty green field.

On the other hand, just because you are working with an animation, you cannot simply fill the scene with everything in terms of 3D models to Lumion. Your workstation has limits, and the same applies to Lumion. You can obviously work with layers, but there is something else that can help you work with big and complex scenes...