1) Don't think I want to add a lean to on the shedCould you take part of the $12,000 you were going to spend on the new boiler and build a lean to off the side or back of your current shed/barn/garage for more toy storage?
Would you consider removing the DHW from the garn and use a heat pump water heater or on demand propane water heater? Add Outdoor reset? both will reduce wood usage.
I have a Garn 2000 and it does take up almost a 1/4 of my barn. I picked the garn after the barn was built. I would have put the garn in the lean to or built the barn bigger. I still can use the space over the garn for storage. (12 ft walls in barn)
A good friend of mine and his brother both have outdoor non gasser boilers and use 10-12 cord of wood, while we used 5 , we all have the same amount of people and similar heat loads. I am assuming the heatmaster and polar are probably more efficient than these older two non gasification boilers.
As already mentioned that would be some expensive square feet for "toys". Are you on a small lot or why not build a small barn? 12,000 would build a decent barn even in today's market. The space savings can't be that significant.Would like to free up some shed space