It got down below freezing last night, and despite my excellent insulating job on 1/2 of the shop, the heater still needed a bit of help to make things reasonably warm in there. To that end, I'm planning on making my shop smalller this weekend. In addition to finishing my lathe stand and stuffing more insulation in the last remaining walls, I'm going to go pick up about 6 sheets of the blue ridgid insulating sheets and make a ceiling at about the 10' or so level. I'm going to screw them onto the bottom of the joists under the loft, and then put some cleats along the wall to hold up some sheets to keep the heat down where it is useful. I'm also going to be up and down my ladder a bunch, installing soffits and some 1/2" ply to cover the gaps in the upper walls where snow blew in last winter.
If I have any energy left, I'm also going to build a solar heater or two out of left over 1/2" ply. basically a two chambered box that pumps warm air into the shop when it is sunny, and stops when the sun goes down. A few 2x4's, some black paint and I'll be in business!