Clay pipes for AC ducts?

Hi there,

I know that this is an odd thought. I have an unusual house, it was an old mechanics garage built in 1934 and now we live in it. You can see it here:
http://1923mills.blogspot.com if you are interested. Anyway, much of the house requires exposed ducting for A.C. (heat is in-slab radiant) and I don't really like any of the standard duct options from an aesthetics point of view. As you can see if you check out the blog design is very important to me. I was thinking about using clay pipes as ducts for the AC. Clearly there are drawbacks compared to metal for a regular situation (namely weight and extra time) but my structure can easily handle the weight and I would be doing all the duct work myself and I don't mind some extra work. Does anyone see any problems that clay ducts might cause? I would think condensation would not be a problem. Would the ducts themselves have to cool down leading to an inefficient system?

It sure would look pretty but obviously function is most important.

Thanks you so much for any insight or thoughts.

Drew