Sorry, It's been a while since I've checked this Site. If I'm heating my garage too, and the temps are below freezing, I have to fully load the boiler twice a day, (morning & evening). At the same temps, if I close or nearly close down the garage zone, I still load it twice a day, but each time it's only about half of a load instead of a full load each time. I was having some initial problems with my aquastat not triggering the blower, so when it began working, I had left the temp differential set at 5 degrees from before while I was trouble shooting it. A few days later, while inspecting everything to see why it was burning SO much wood and having really short burn times, I discovered what I had done and set it back to a 15 degrees, per the instructions. This decreased the wood consumption by quite a bit. I had a little bit of a learning curve, but I think that I've got it figured out now.
One of the 8 zones, (within the original structure), doesn't currently have an automatic zone valve on it. It has a thermostat, and wires that run into my water closet, but no zone valve. How silly is that... Anyway, as the seasons change and we turn the heat off for the year, I plan on installing one. Then we'll have thermostatic controlled zone valves on 7 of the 8 zones and my wood consumption should go down even more. I tentatively plan on installing a thermostat and zone valve inside my garage to operate the garage zone too, after I get the construction materials and tools moved out and I start spending more time in there working on my hobbies. My garage zone is controlled via a manual ball valve currently and it's tough to get a constant inside temp as the outside temps change.
I'm extremely happy with my choice to install a wood burning boiler! The propane bill would have broke the bank...