How to Create Floors (Storeys) Inside a Generated Volume??

Hi there, 

I am doing research on solar envelope zoning. Essentially, the solar envelope is a volume that is generated on a given site based on the movement of the sun. Grasshopper has great tools for this. 

Now that the envelope volume is generated, I would like to generate floors inside this volume (height of 4.5m ground floor, 3m for subsequent floors) so that I can evaluate the maximum floor area, and compare to other zoning techniques.

I have am now stuck. I have generated the floor planes, and I have generated the envelope volume. Currently, my model will "trim" the floor area out of the floor planes, but I want it to do the opposite - keep everything in the volume and remove the rest. 

Any help is very much appreciated. See attached .gh