Plumbing and cold weather (Re-post)?

I posted the following a couple of days ago but I think everyone took advantage of the wk'nd. :) Thanks. Plumbing and cold weather? We're rehabbing an old brick school house (circa 1908) in central Mn. Many years ago a large addition was added to one side with a block foundation crawl space and 2x6 floors and the plan is install a 1/2 bath and laundry room into a portion of the addition. Currently there is no heat, never was, (we've got a hvac people coming out to analyze this and several other issues) and we don't know yet if we'll be using forced air, baseboard heat, or another method. I finally convinced my partners that the sink and washer will go on interior walls. Because the crawlspace has no entrance once the floor is put back in it'll be basically sealed. Since I'm the amateur plumber that has to make this work and I'm starting to get hammered about getting started I thought I'd get some opinions about my concerns. My main concern is how avoid freezing pipes. (It gets cold (-20) up here) I can route through a 14" foundation into the crawl space or possibly go thru the main building at a higher level with minor modification to the kitchen plan. Would it be recommended to run the pipes down from the ceiling or under the floor? (Only 2x6 floor so I don't trust the insulation to keep warm) Heat tape? Run lines thru the cold air return? I keep hearing ... "they do to mobile homes all the time!" to the point I'm ready to snap.:) Should any special attention be paid to the drain lines? I'm ready to listen even to unconventional ideas. Thanks Yes, this has a basement and we could go either straight thru to the crawl space or by going up to main floor and then over into the addition. The number and size of the holes needed at this time are not a concern. thanks