Hi Bob; welcome to permies! Yes you can heat your garage with a RHM . Recommended to build a core & riser outdoors to get the hang of it but then you would build your RMH in place. The builders guide by Ernie & Erica Wisner readily available on amazon will have all the tech info your wanting. Two different burner styles , the original J tube design or the newer batch box version. Both are outstanding. J tubes are quick and relatively easy to build , batch boxes are much more technical to build but burn slightly longer and hotter than a J tube. There is currently a batch box core built with ceramic fiber board and stainless steel that is available on Ebay , produced by a permies member. As your first rmh I recommend a J tube ... you can always upgrade to a batch box later.
Not all who wander are lost... J.R.R. Tolkien
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