I was looking for a thread like this, but a couple searches didn't turn it up, so...
As I listen to the Permies Podcast the question often comes up of why there aren't more RMHs in the world. I figure a thread detailing the reasons people who know about them, yet chose something else, might be helpful in identifying the barriers. I fall into that category.
My parents built a house with a masonry heater (kind of like a batch box RMH, except a millennia old design that works beautifully, though perhaps a tad less efficiently), so I was already familiar with the idea of super efficient wood heat, and took what I read online at face value. I got the Better Wood Heat DVD, and watched enough of it to get an idea of how they work and what is involved in building one. I've never actually experienced one in action as nobody I personally know has one, but like I said - I believe they work as advertised.
A few years ago, we bought a house. It is split level, meaning the "first floor" is a walk out, mostly above ground basement, while the second floor is the living space. It is in an unincorporated US town, and the county has pretty normal regulations - meaning you are supposed to get a permit for structural house modifications and anything fire related inside your house. The house already had a a working open fireplace on the upper level and an old timberline stove in the basement - so two chimneys for wood burning, plus an oil furnace.
At this point, I started looking more seriously at my wood heating options. The house came with 5 acres, and in procuring some woodchips from local arborists, we sortakinda accidentally ended up with a flippin ENORMOUS pile of wood for free.
So; what was my perception of the barriers to building an RMH?
1) I didn't know if the upper floor would handle the weight. I am a pretty advanced DIYer, but I do call in pros for things that might actually break my house. So, in order to overcome this, I would hire a structural engineer to assess. And then, possibly, rip out the basement ceiling to install bracing/sister joists. Added complication: the ceiling paint is textured and has asbestos (WTF 1980s???), so we'd have to push up the plan to hire a decon company to take that out. So likely a fairly pricey remodel.
2) I have a mortgage, and so am required to carry home insurance. I didn't look too into how an RMH would be viewed by Geico, but I had read on the internets that this is a problem, so it was definitely an added barrier.
3) County permit. I hate paperwork with a passion, and the thought of trying to navigate this practically makes me break out in hives.
4) The actual build. I know there are books and videos, but my experience in DIYing tells me that each situation is unique, and since I've never built one or even seen one running, I was not confident that I knew what I needed to do to ensure it would work in my context. Would it work to install a stovepipe in the chimney and have it go out that way? Or would I have to cut a separate hole in my ceiling and roof? I felt like I needed to put a lot more time into researching it to more fully understand it, and even then I would be nervous, as it just seems like such a huge project, and hard to fix mistakes.
5) Prepping the barrels. I picked up two 50 gallon drums for free early on, but burning off the paint in a non-toxic way seems scary. Yes, I know this is a ridiculously small obstacle, but there it is...
So; all of this added up to the feeling that it would take a lot of time and money to install a rocket mass heater. With everything else going on around here, the time component meant it would probably take years. The alternative was to get a fireplace insert that slotted into the existing upper floor fireplace. This is what we did. For ~$5k, we went to a local stove store. They came out and measured the fireplace, and told us what would be required for each insert we liked the look of. They installed a chimney pipe down the chimney, applied for the permit, carried the insert up the stairs, and installed it. Within two months, we had wood heat, with the stove and installation guaranteed for a year by a reputable company with all the relevant certifications. In our climate, we've had the oil furnace turned off for the past week, and been completely comfortable. I seem to live in an area where I can get all the free wood I'll ever need, though I need to cut and split it.
An RMH, if I'd gone with that, would have reduced the amount of wood I have to cut and split. It also would have reduced or eliminated the need to clean the chimney every year, and reduced my guilt about running a stove that is releasing global warming gunk into the air. But building an RMH felt like it would mean another couple of years on oil, possibly be more expensive, and with no guarantees that it would work at the end. I know I could have paid someone to come out and consult, but that is not the same as having a company that will just come out and fix it if something isn't working in the first year.
So, there it is. I haven't totally given up on building one eventually - we've always meant to turn the lower level into an in-law suite, and the concrete floor down there seems much more likely to handle the weight, so the trouble an expense of the home renovation wouldn't be there. I don't know when it will happen with all the other projects around the land, but I'm hopeful in a few years I might have time to start attacking the other things on my barriers list.
Anyone else want to share their barriers to building on of these things? Hopefully it will be helpful to those wanting to move the technology further!