@Benjofen - Nice view from your balcony. The fog makes it hard to tell what direction you are facing. I'd guess you are up north near Loyola, Sheridan Road and Petersen or Devon, or you are down near University of Chicago. You could be just south of the Loop. Am I right on one of my 3 guesses?
For wintering, all the azaleas have enough "sub-tropical genes" that wintering them in your unheated room might be better. The 50 F will hold them semi-dormant for much of the winter. If you use modern LED, you should have enough light intensity that if they do start growing, you can keep the foliage compact. Leave them outside until temps are cold enough that you are getting frosts regularly. Move them to the unheated room when night time temps are supposed to go below 28 F. The hardy Girard azaleas should actually do okay freezing solid. The ground normally stays quite a bit warmer than air temp, I really would not allow the roots to freeze below about 28 F. In the Chicago area, most of the azaleas sold for landscape use are the Deciduous types, and I have found they do not survive our winters unless the pot is buried into the ground.
Myself, I gave up on trying to winter azalea outdoors. So my collection is mostly the more subtropical, zone 7 & 8 azalea, I winter mine in my underground well house, in complete darkness. They come out in spring when the leaves of landscape maples (street trees) are about 25% to 50% unfurled. They come out after the Norway maples have flowered, they flower while leafless, once the Norway maples start to unfurl leaves, it is usually safe to bring trees out from winter shelter.
I have also wintered azaleas, especially "florist's azaleas" under lights with my orchids. This light set up was in the basement, and temps would be in the middle to low 60's F when the lights were off (night). The lights would heat up the room a few degrees. Most azalea have enough "sub-tropical genes" that wintering in the low 60s is possible. they may bloom a month or two earlier than they would when wintered in the ground or a well house, but since you don't have any ground, and are not lucky enough to live in a 100 year old house that came equipped with a well house, your unheated room is a safer bet. The zone 5 hardy azalea are "barely zone 5 hardy".
I have found spruce, Black Hills Picea glauca var, and Picea orientalis and Picea pugens the Colorado blue spruce, Pinus sylvestris, Pinus banksiana, mugo pine, Canadian hemlock, Siberian elm, both American hornbeam and Korean hornbeam, Amelanchier, crabapple (Malus), and a fair number of other trees listed hardy into zone 4b or colder to be hardy enough that I just follow the "drop or plop" method of just setting their pots on the ground for the winter. No healing in, no fancy plastic tents, pile a few leaves around. Often leaves get blown away before spring. These species likely will do well on your balcony all winter. I would take some cheap beer coolers, set the trees inside, add a half filled with water plastic soda bottle or two for "Thermal Mass", then tape the coolers shut for the winter. Stack them against the outer wall of the building and forget them. The water in the pop bottles will slow freezing in the cooler, and slow thawing in the cooler. This will help lessen "Freeze-Thaw Cycling". Most trees do great if they freeze once, stay frozen all winter, then thaw in spring. It is rapid freeze-thaw cycling that is really rough on trees.
I have had good luck just setting a normal form "lacebark" Chinese elm on the ground. It has survived the last 5 winters that way. I got mine from Brussel's. But many have had trouble wintering Chinese elm in the Chicago area, so while "Plop or Drop" technique works for me, I have heard many have trouble. The Chinese elm cultivars 'Seiju' and 'Corticosa' do not survive my "Plop n Drop' technique. I found I have to winter them in my unheated well house.
Siberian elms are everywhere in the city, Ulmus pumila, and I found them pretty good so far for bonsai. Mine are still in Anderson flats. They form a nice rough bark relatively young (decade or so). They are "free" as they are a wildly invasive weed around the city. They do require full sun, sunrise to sunset sun, if one side of the tree gets shaded too long, it will drop branches on the shaded side of the tree, so rotate them often. Other than the need for full sun, they are super hardy, drought tolerant and decent, small leaf, twiggy elm.
