I came into my build with the same goals and concerns as you. I have three kids ages 4 and under, so I didn't put anything into mine that I wasn't sure was safe. Every bit of research I did lead me to believe that the hardiboard is safe. The only real dangers is during cutting, when you have a risk of breathing in the particles.
As for plywood, I found some at Home Depot with a soy based glue. It doesn't have any of the nasty stuff that regular plywood has.
But mine was also a multi-use build. Its roughly 2'x2'x6.5' and runs off charcoal. It worked great for bbq-ing in August and September, but got very hard to control when the weather started to get cold. I haven't bothered to run it in a few months. Its just too hard to keep the temperature up. In the next couple weeks, I'm going to throw a propane burner and pellet tube in there to try to make it usable.
So to answer your question, there are safe materials to build it out of. But don't bother to make it both a smoker and bbq-er. Its just not worth it. Once I get enough use out of this to justify it, I'll be designating it for just a smoker and find myself a nice offset for cooking.
Hi
@Nate52, after doing more research myself, I agree that the hardiboard is safe once you are done cutting it. As far as the plywood, I looked at the product you are describing. Unfortunately, there is no Home Depot anywhere close to me (one of the disadvantages of living in South Dakota), and they don't deliver this particular product.
After doing even more research, I have come to the conclusion that I am going to use wood boards, insulation, and drywall for my construction. I have fiberglass insulation from a roofing project that will otherwise likely go to waste, and I will sandwich that in between the wood and the drywall, so I don't have to worry about any fiberglass getting into the smoking chamber. Why drywall vs. hardiboard? Roughly the same price, MUCH lighter (1/2 the weight) per square foot, better thermal mass, and lower U-value/higher R-value. Why wood vs. drywall? Same reasons - for 1" thickness for both products, wood is cheaper (by about 1/3), lighter (by about 1/3), ever so slightly better thermal mass (planning to use pine, so it has a better thermal mass than a hardwood), and lower U-value/higher R value.
There was one other major factor that went into my thought process. To me, it's an indication of a product's safety when certain items such as plywood and hardiboard have Safety Data Sheets listed on their websites, and products such as pine boards and drywall have none. It's an assumption on my part, but I would think that the latter two products would need them if safety were a major concern.
If I want to take safety to another level to virtually eliminate any chance of the smokehouse catching on fire, I can line it in aluminum or steel.
Is this going to be heavy? Without a doubt, this will be a beast of a unit, likely coming in at around 300-350 pounds if I stick to my original specs. It would be even worse if I use plywood and hardiboard. I was originally thinking of making this a portable unit, but I am more interested in temperature stability, leading to a better finished food product, than portability. If push comes to shove, I can always move it with a 2-wheel cart.
indaswamp
. If I were to go with a hybrid system, this is essentially what I was thinking. The main issue I have with lining the inside with hardi board is the reason for the title of this thread. All of the cement board / tile backer / hardi board I have looked at contains silica. I have been unable to find any definitive evidence regarding the safety of the different types of cement board. For that matter, I also wonder about using plywood. The binders in that can be an issue. Obviously, I would never get the smoker to the point of needing to worry about the melting point of the various substances. I am just concerned about the potential for off-gassing of any product. Perhaps that can be taken care of by doing a couple burn-off sessions.
