That's a LOT of firewood!!! Your boiler must really go through it on bitter cold nights...
It's heating the house, farm shop and well house for a total of around 10,000sq/ft. When it's -25f and windy it'll eat a cord in 4-5 days. Granted it's mostly poplar, elm, cottonwood and boxelder with a few pieces of ash mixed in so it's not on the most efficient diet.
I've been debating the cost of a building too. On your farm it must be hard to justify if it's not a money-maker. Could you think of it like this: how much $$ have you saved by not paying to run your house furnace? Is the boiler making you money by allowing the profits from your business to go directly into your pocket, rather than into the furnace?
The wood boiler offsets around 2,500gal of LP a year so this year it saved around $4,000. It'll take a while to pay for it all even saving $4k a year. I figure between the stove, pipe, concrete pad, pumps and everything to make it run I had around $32,000 invested. Then it gets a little iffy with expenses ... such as ... does the $5,200 grapple I bought for the skiddy count against the stove ? The $4,000 wood splitter definitely does. What about the probably $3k in chainsaws and wood cutting stuff .... or the $17,000 dump trailer ..... or even the loader on the lawnmower ? If you count it all in it'll be a 17yr payback with todays LP cost. Not horrid but I want things to cash flow in 7yrs or less, ideally 3-4yrs or less.
The shed adds value to me in the way that I won't have to stand in the cold and wind to load it. That's about it. The stove doesn't really seem to care about a half inch of ice on the wood when it goes in. It'll be a little less efficient of course but I have lots of wood here so the lack of efficiency would have to offset the amount of wood it burns. If it burns another cord or two a year that isn't big a deal really. I can have a cord of wood cut up pretty quickly and I pay nothing for the wood. There are two people and two tree services bringing wood here all year long and I don't honestly know if I can get it all burnt each year so another couple cord if the wood is snowy isn't a big deal at this point.
Plus I'm tight and don't like spending money unless I see a direct benefit to more than just convenience for myself or others.