Do unfermentable malts exist?

[jayhawk]

For some reason, I have a notion that Dextrine/Cara-pils, and Crystal malts are not fermentable. Is this true? Can yeast ferment the carbs derived from these malts?

The reason I want to know is I am trying to make a rich old fashioned rootbeer and I want it sweeeeet with lots of body. Alcohol is a low priority.

[fitz]

Don't use the yeast to carbonate.
I know it wouldn't be quite true to form of the old fashioned, but if you carbonate in your keg, instead of the yeast, you can use whatever you like. You could use lactose, to sweeten, but then it would be cloudy. If you go the keg route, make sure you change seals, and hose ect. before you use it for beer. You can't get the smell or taste of rootbeer out of them.