Terri

I am in zone 5.

The first time I wintered over my basjoo I covered it with a cardboard box (I cut the top off the plant so it would fit) and then I made a large heap of leaves over it. I uncovered it in the spring.

This actually worked quite well! The top was like mush when I uncovered it and I thought that I had lost the plant, but it did successfully break dormancy. Since your plants are against the building they will be better protected than mine were: mine were on the far side of the vegetable garden!