空房 would be pronounced kong1fang2, right?
It is interesting that we picked the tone subconsciously. Although we've been following some guidelines, we never noticed that. Even being asked, after thinking, few people can tell the guideline.Edit again (please disregard the above)- No, I was deceived. I just thought about 空碗 空瓶 空盒 空井 etc. and had to agree with Super XW. We use kong1 when referring to the physical status of a container, and kong4 when expressing that something is not occupied/used/claimed. Therefore 空房 can be pronounced either way depending on what you want to stress- that the rooms (房间 is better here) or suites are empty (kong1) or that nobody is living or using them (kong4).
That's surprising.few people can tell the guideline.