Rhino file increasing in size during export to Obj / Fbx

My Rhino file is very large. I’ve separated it into “smaller” files and am trying to export each file so that I can bring it to twin motion to render. When I exported to Obj file a 560 MB file became 12 GB. I do not understand why. I have tried making things meshes, blocks, reducing mesh detail, etc. Does anyone know what could be causing this? My model is made up of many individual pieces. I’ve attached an image of one ‘hut’ model. Really at a loss here as I’m doing what I can to reduce file size and nothing seems to be working. Any help is very much appreciated. Thanks notent|465x499

Hello - a couple of things - one is that OBJ is a text format, not binary, and OBJ does not care about blocks. It might help to mesh all of your objects using custom, efficient, mesh settings ( see https://wiki.mcneel.com/rhino/meshfaq ) and Join the parts that should be the same into a single mesh before exporting, but the text format will be larger.