Hello. Soon to close on this house in Boston area
http://tinyurl.com/laef824

You can see the 3 season porch on both first and second floor. There is no bathroom on 1st floor, and we would like to convert the porch to a 4 season as well as add a half bath. The porch is outside the foundation and basement footprint. Here is photo inside the porch
http://tinyurl.com/lsfh53h

The issues of converting to 4 season (structural, heating, windows, etc) I believe I understand, but plumbing the bathroom I need some help / opinions on. What are my options for getting the plumbing in / out of the basement? I don't believe I can slope into the adjoining room (dining room) and down into the floor, so it seems my other option is through the foundation. What then of pipe freezing issues?

It would seem this problem is somewhat common (additions outside the original structure with a bathroom), but google searching is nearly impossible, returning 1,000 ideas on basement bathrooms.

Thanks!