I've only heard about external water pipes when somebody wants to rant about how bad some british houses are. Pipes on the outside, separate taps for hot and cold, carpeted bathrooms, poor insulation with drafts. I've never seen it done in reality even in houses several hundred years old, and in Michigan they would freeze as soon as winter arrives.
You can put insulation and siding over the pipes outside what is currently the house (and remove insulation inside if necessary). That way the pipes will stay at the same temperature as the inside of the house. Or, as https://news.ycombinator.com/item?id=30878006, heat tape. As an extra bonus, if they do freeze, they'll leak outside the house instead of flooding inside the house.
