Fireplaces, Heating Stoves, Flues and Chimneys - Do I have to use insulated chimney, can I make my own

I am currently building a house, my wife and I have done all the work paying as we go. Now, we have a woodstove upstairs and a wood furnace in our unfinished "basement" (8ft crawlspace)We're going to run 2 chimneys, was originally going to have them share one but have since read that that isnt safe. Anyway, Is there anyway around buying the outrageously expensive insulated chimney pipe? I live in TN and the winters arent usually very cold. One chimney will be about 10 ft long (after leaves house), the other will be about 24 ft long. i remember reading somewhere that you could make a crude insulated pipe using a 6 inch pipe inside of an 8 inch pipe, screwed together with 1 inch copper pipe pieces as spacers. Has anyone ever heard of this or used it. I also thought about adding some ceramic insulation between these if it isnt too expensive, but i dont know where I can buy it. (since the building sits 8 ft off the ground a stone chimney would be very impractical, not going to happen)