An unattached garage might get much colder than you think. It will probably be too cold for most of the tender stuff (elephant ears and cannas). If you want to experiment try a tub with soil or dry peat moss and bury the pineapple lilies and glads in there. Maybe using a cheap styrofoam cooler will help protect them.
If its cold for more than a day or two it doesn't matter how well they are protected.... Insulation wont stop the cold from getting in, it will only slow it down.
you could bring them into the basement for the worst of the winter.

Thanks for the advice. I'm thinking the elephant ears will do fine at room temp, so those I'll bring in. Cannas - the coolest place I can think of in the house would be my attic, which probably gets in the upper 50s low 60s during winter.

As for the glads, I guess maybe I'll experiment with keeping some out in the garage and some in the house and see if any survive. If not, I guess I could just buy another pack of bulbs next year. Or, as you say, keep them outside in the milder weather and bring them indoors when we get a cold snap.

I have the same problems with cannas. We have an unheated, uninsulated chicken coop and a pool house that is insulated but unheated. I've put them in the poolhouse. Is that ok?Zone 7. (snow in winter)

I grow them in various places around the yard. I dig them all up in the fall, except the ones planted next to the South foundation of my house, which I dig up in the spring, mainly because they multiply so much that I have to thin them.