Rush at Idaho is before school starts and women move in on Bid Day as they are temporarily housed in the dorms during rush. In the past women have lived in the dorms if there is overflow, but having the freshmen fill the house makes it easy for older members to move out into apartments and it isn't hard to find an apartment in Moscow at all.
All of our current nine houses have sleeping porches, and I assume Delta Zeta will design their forthcoming home the same way. Delta Zeta has their own space in the dorms until they have their building constructed, and I don't think they have broken ground yet. Though I don't know the inner details of every chapter, as far as I know it was common for new and some current members to change rooms every so often during the school year to get to know more women and I secretly think to make them clean their rooms regularly
As of fall 2010 all freshmen at Idaho are required to live on campus, which includes Greek housing.
In previous overflow situations it wasn't only new members living in the dorms, some older members would go with them, and meals were eaten at the house, the meal plan was waived. Though dorms have people sleeping in their rooms and not porch style, one dorm had suites where the beds were in between with the bathroom. There would be a rotation of women into the house from the dorms and usually at semester/mid year women would move out for study abroad, practicum, internship, flunking out, and graduation. Though there may be individual organizational rules against it, being in the dorm wasn't completely undesirable as one could legally have alcohol if they were 21, sometimes less people fighting for the bathroom, and in some cases closer to classes. I'm sure there are probably stricter alcohol rules than in the past if it is a designated sorority floor or a mix of upper and lower class women.
Unlike a lot of places there is no housing crunch on campus or in town for traditional undergraduates so older girls can willingly, easily and happily get an off campus apartment and make room for new members to move in. Students are told to not sign housing contracts if they plan to rush, and since freshmen are required to live on campus there are not left homeless. If any student leaves Greek housing after school starts they will be given on campus housing if they are freshmen, or like I mentioned, can move off campus. There was a massive resort like complex built on the south edge of town that is fully furnished and rather popular, so there isn't a problem of living without furniture until it can be bought or brought from home.
I'll honestly say I am not a fan of rush before school starts nor freshmen moving in on bid day. I see a lot of benefit to having all freshmen (men and women) live in the dorms the first year and then move in as sophomores if delaying rush would be an unacceptable idea. As a campus we're damn lucky that the administration will include and allow Greek housing to be approved for freshmen as many places it isn't.