I wish it were that easy lol. Passies actually are a bit more work to overwinter. There are some that I have that I have to bring in, even here in zone 9.
Passiflora need light to survive. If they were kept in the dark basement they would probably die. When I lived in a zone 4, I kept my plumeria and brugmansia downstairs (dark basement) and my passies upstairs (with grow lights).

If it is warm enough, maybe you could make a small area in the basement for them , and set up a grow light. They need to be kept above freezing and some of the tropical ones need to be kept above 50 degrees.
You will also have to watch for spider mites which love the warm dry conditions in the house. Misting the leaves helps with this.

Also although they need good ventilation, don't place them directly near or in front of heat vents because this will dry out the leaves too much.

Keep them on the dry side and only water when slightly dry.

I am posting the link to passionflow that has alot of info. on passies. You can also do a search of this site on overwintering for further ideas.
~SJN

Here is a link that might be useful: overwintering passiflora

Thanks for the link. I am just starting into passiflora and would really like to keep them as happy as possible.

Billy