My guess is it will be "check with your tax advisor " type of question. Reportedly there was a lot of latitude allowed on solar for support systems like roof replacements, household panel upgrades and trench excavation that could be used for other purposes other than solar. My speculation is its one of these things that you might get an inquiry from the IRS to give them further explanation but it will not result in fine rather they just disallow some or part of the credit and you get to write them a check. I would make darn certain that it was a single purpose structure not used for anything except the wood boiler components.What is the thought on if this credit would apply for building a "boiler house" to house the equipment? I don't have space inside to install a gasifier, tanks, controls, and I would want/need to build an adjacent boiler house.