I am in the planning stages of building a chimney for my garage. I haven't figured out how many flues I am going to put up yet, but it will be at least 2. The chimney will be of masonry construction. The garage is 2x6 balloon framed, built in the 1930s, i.e. well seasoned. I plan to be heating the garage primarily with coal, but I would like to have the option of burning wood as well.
I want to build something that not just meets, but far exceeds any safety requirements. I'm talking about the chimney that is so robust, that if you have a roarin' chimney fire, you sit around, drink beer, and make youtube videos of it, instead of having to call the fire co and worry that your shop is going to burn to the ground. I'm exaggerating a bit, I wouldn't sit around and watch a chimney fire for fun, but I want a very high margin of safety built in.
I've been trying to think of ways to do this. One thing I thought of, would be to put some type of insulation (vermiculte?) between the brick and a 12"x12" liner, then put an 8" round liner inside the 12x12 and put more insulation between the 2 liners. Any other suggestions?