The safest course would be to provide some root protection for them. May not be necessary in most Z6a winters, but no harm in having it. As for where... Fully dormant plants do not need light, so that condition does not disqualify the crawl space. Watering should also not be necessary. Wrapping each pot with bubble wrap or another type of insulation then placing the pots close together in the barn, then wrapping the whole should be fine, too. Placing a large carton - I've used rigid styrofoam to make a "carton" big enough - over everything to capture some ground heat is frequently recommended but would not be relevant if there is no ground contact between the barn floor and the earth. You also want to be careful of mice and voles. Some years they do not present a problem, but last winter I found voles to be a major headache. Trapping is probably most effective.

Jim Kohut describes Morden 9703 (S16) - A recently introduced (and as of yet unnamed) hybrid from Eastern Europe, this is undoubtedly the hardiest green table grape you'll find. Produces absolutely enormous clusters of large green grapes that are incredible for fresh eating, especially if left to ripen on the vine into fall - these will rival any table grapes you'll find in the store! Hard to find in the trade. Marginally hardy in zone 3 - may need some winter protection." Make it Green garden center lists it, whether it is what they say it is is another matter. The front here would be Prairie Star but I was busy and the vines co mingled together...I did trim a few times but the wet summer created a lot of vigor. The clusters look good but I will have to follow the cordons back as they should not be colouring. If they are they would most likely would be the Frontenac if the clusters continue to change colour. There was no die back anywhere but this was an unusually mild winter. Probably could be described as a zone 4 rating. Frontenac on the left.

Under the snow, my voles make little nests out of grass that look like mini-yurts. And they'll hide in them as the snow melts, and you can see them looking out at you. Their little trails in the grass are all greener in the spring from their urine, I suppose. They've wiped out two large grape vines, a swamp oak, two fruit trees, and they seem to do a number on several perennial flowers as well. Gophers do the serious digging and recycling, and there is one who moved into the raised garlic bed sometime yesterday, and when it stops raining, he will be flushed out by running irrigation water down the hole. The ground squirrels seem to find something nice, condo-wise, under the south house foundation. Busy busy busy. Across the fence we have a prairie dog colony. Yesterday, there were two large hawks on the ground, having one for breakfast.

That will be to warm in my opinion. I would bury them in soil and hope for snow cover. Most likely you will cut them back once planted, so of the vine gets damaged that's not a big deal. Protect the roots.