Rich and others will give you more specific and better advice but I will start off and tell you what I do here in western NY which may be a little colder in winter depending on the area of PA you are in.

I don't have a basement at all and my garage is detached from the house and gets way too cold. I do have an unheated mud room on the north side of the house but it is too small for more than two or three decent sized plants but it gets good light. My best natural light is in the living room but it stays a bit too warm. My sewing room also gets great light in winter but it also stays a bit on the warm side. Both face directly south.

I have overwintered Salvia guaranitca and a couple of small greggiis in my kitchen which has french doors on the west side of the room. I have tip pruned the larger plants just a little. I put them in front of the windows which also have UV glass but worked well. I closed off the heat vents in that area completely. I watered lightly as the soil began to dry. I also overwinter my Gartenmeister fuchsias there and they did beautifully. I took cuttings of those over the winter and had a dozen new plants by spring. I lightly watered those also. I have overwintered a manettia in the same window along with passion vines The only plants that didn't do as well inside were my agastaches. They were stressed but they did survive. I even overwintered my Baja Fairy Dusters in an east facing window and watered when the soil was dry.

Oh for the plants in the kitchen (salvias, fuchsias, etc. I mist them occasionally to help counteract the dry air and prevent white fly.

This year I am doing more cuttings of my plants rather than bringing the full size plants inside as I think they will be much easier to maintain.

Penny

I cluttered my kitchen with some tender plants and one salvia. It lost most of its leaves and I kept it on the dry side and in spring, it bloomed profusely- I think it was La Trinidad Pink.

Would they survive in northern Indiana in my unheated but well insolated attic? I have windows facing all directions too.

One option instead of trying to keep the plants unfrozen and more or less green all winter is to let them get frosted then winter them in a dormant condition. This could work for the Salvia greggii, S. elegans, and the Gartenmeister fuchsia, I am not sure about the others. To do this leave them outside to experience increasingly shorter and colder days. I might choose a sheltered spot to delay frosting them as long as possible without bringing them inside. Eventually a frost or two will kill the tops, them you will take them to shelter before the ground in the pots freezes. I'd put them in a cool but not freezing location, keep them dry but not bone-dry, and try to delay their resprouting until April by keeping them consistently in the 40s or so if possible. Once they begin to sprout they'll need bright light but can still be cool as long as they don't freeze. Cooler conditions will make them grow more slowly and help prevent you having to deal with three foot tall indoor plants in March. One way to accomplish this same thing is to place the pots up against the house and bury them in a very large pile of leaves to keep them unfrozen but cold all winter. They should resprout in the spring.

All three of these species can survive in the ground just a little south of where you live, so you're trying to take the edge off of the winter weather without having to provide suitable conditions for active growth all winter. Sustaining active growth in a normal house is kind of tricky through the darkest months of december, january, and february, but becomes a lot easier in march and april.

Thanks, everyone, for your help! I was terrified that I would not get my plants in before it frosted. It's great to know that I still could have saved them if it happened. I thought it was an all or nothing situation (ie frost = death).

Everything is now inside. Of course, most are blooming and look spectacular. It is soooo hard to cut them back. The upper attic like room seems to be staying right around 55, so I plan on moving most of them up there. Luckily, I have several pots of each variety, so I'm going to try some in the sun room, too. Plus, I took cuttings. Hopefully, redundancy is key :).

Thanks again,
Bellatrix