How do you handle the seams on exposed (no additional cladding) metal SIPs?  I would guess that tape would be a bit ugly, but maybe not if done carefully and given a good paint job.  Is it rather overlapping skins screwed together with caulk or adhesive?  Same for horizontal and vertical joins?

rnortman;

there are no fasteners in seams, all seams are vertical and if they are to be left exposed they need to be caulked as shown on the picture below

I went to the Museum of Modern Art (MOMA) in New York yesterday and spent a while looking at the Jean Prouve steel panels. He had three types, A full steel wall, the exterior had mini-corrugation, the inside was smooth steel. One had a window in it, and the other was a door.

I can't find any images on the web, but a modern version could be an option for a low cost house.

I am curious of how you connected the Hardie to the soffit. Was it nailed and glued? With the lack of solid wood members to nail into, was the soffit attached in a manner that would pass inspection/code? I am working on a project now that will have the OSB SIP panels and the Hardie-Soffit. My concerns are about attaching the Hardie-Soffit to the OSB. Hardie doesn't have an answer nor do they want to help. Way to stick by your customers! Anyone have some input on this? I really appreciate it.

Chris,
In your last pic I'm assuming the seam is the narrow channel? Why the giveaway, can you get panels in which the installed seam matches the width of the grooves in the field of the panel?

Nope;

but they are perfectly acceptable for exposed soffit, the prevoius picture was taken just 1 foot away.
Stand back a little like this picture :)

slenzen,

Most Metal SIP manufacturers use metal skins that have what is called a "stucco embossed" finish. It is like a low relief "pebbley" finish. This is good for hiding small imperfections, dents and maring on the metal's surface that may occur when they are handeled. It looks somewhat like stucco but is a little too regular of a pattern. From 30' in the sunshine you could not distingush between cement stucco and the embossing, except for the panel joints every 40-48"