Differences in thermal results of simple room, can someone please explain?

[Anonymous]

Attached is a zip file with three almost identical simple models of a single room and the three image files (jpg) of the thermal results.



The single room is 22ft high and 40x40ft.

The other two models replace the top 4ft with an 'attic' zone, so the room is now 18ft.

All materials are kept identical in all cases except the 'room ceiling to attic floor' which is either VOID or PARTITION.



When I use a VOID between the room and an attic space I get different results than just the room without the attic, I believe these should be identical since the overall height of the room has not changed and the attic uses the same wall material.



But the weird thing is that when I replace the VOID with PARTITION I *do* get the results as just the room itself without the attic (what I would have expected from the VOID).



I believe there is something fundamental I am missing here, if anyone can clear this up. The models are extremely simple and only take a minute to run thermal analysis.



thank you.

Jeff