More CAD drawing last night. Up until about 12:30.
Started off with the site plan. That actually went fairly well.
I got the front elevation done, and realized that I needed to make a couple of changes to both the side elevation and the plan view that will make the construction easier, and I ran into a funky problem that puzzled me all last night... and this morning in the shower I figured it out. So I have to do more fixes tonight.
It's not your basic stick-built construction-- it's all post-and-beam, so it's a little trickier. And I realized last night that the design is much more of an evolutionary process than I had thought it would be: as I do one drawing, it may affect how the pieces go together in another drawing, or I may find a better way of doing something.
Like dealing with a shallow-pitch roof. In this case, the roof slopes something like 4 inches in 10 feet, or a 1:30 slope. Trying to frame that slope is a real nightmare of calculations, so what I ended up with is designing all the framing flat and level (MUCH easier to cut and build), and dealing with the roof slope separately. All it really means is that I have to cut wedges that are 10 feet long and 4" high and attach them to the two side beams, and believe me that is a LOT easier than trying to cut each post to the exact length with a shallow angle.
The boiler update: as it turns out, the boiler ignition is indeed triggered by the thermostat. Technically, the thermostat opens the vent damper and the vent damper triggers the ignition, but the end result is the same. I think I need an aquastat to measure the return temperature and trigger the boiler from that.
While the boiler has a safety feature to shut down the ignition if the temperature goes too high, I'd rather not rely on a safety feature as a part of the normal operation of the boiler.
I could trigger it through the thermostat, and just leave the zone circulators to run continuously. I think I may have to do that for the time being, and just have a lot of faith in the tempering valve to work and not overheat the house during the "warmer" months.
I probably could have designed the system better with a heat exchanger between the boiler and the zones. It would have been a little less efficient, but it would have been much easier to control. The boiler would have been in its own closed loop, and each zone would be in its own closed loop.
Ah, well... remember this for next time.