Keep Warm In The Winter With A Grizzly Wood Stove

Winters here in the Pocono Mountains of eastern Pennsylvania can be brutal, not Alaska brutal, but cold enough to kill you if you don’t have heat. (Actually, one can succumb to hypothermia when it’s in the 60s.) Those of us who call ourselves “preppers” or “survivalists” have dozens of disasters we prep for, economic collapse, mass riots, pandemics, famine, foreign invasion, or the less glamorous, and shorter-lived ones like floods, tornados, or hurricanes. However, the one disaster that many preppers don’t even want to consider preparing for, or even think about, would be nuclear war. The reasons are many. Cost is a huge factor as most pre-built, nuclear shelters, blast- and/or fallout-rated, cost around $100,000 before install. The other issue is knowledge, and it takes a fair amount of study to wrap one’s head around the science of surviving a nuclear strike. Many times, even preppers have latched onto to left-wing propaganda that nuclear war survival is not possible or worth it. This is the same propaganda that gutted our civil defense system in the USA back in the late 1970s. In contrast, many countries in Europe not only have a robust nuclear survival program but have also increased spending in recent years. However, this article isn’t about nuclear survival, it’s about my quest to heat a room which could be converted for use as a nuclear bomb shelter.

Having a farmhouse which is over 100 years old has its advantages and disadvantages. Watch the movie The Money Pit starring Tom Hanks and you will get my drift. The one feature I love about my place in the hills is an underground root cellar which was built with concrete, huge stones, etc. with a cement-slabbed ceiling (some of the construction was done with forms and seems to have been an addition in the last 40 years or so). Although I do garden and hope to do it enough in the future to start canning, I would have to turn this property back into a farm to fill up this 12’x24’ space. The ceiling also has about four feet of earth over the top of it. It’s an almost perfect natural refrigerator which is about 35-55 degrees Fahrenheit all year long – but I’m not a vegetable. If I’m going to make this a place a shelter to protect against radiation, then I had better figure out a way to heat it.  

Other Ways to Heat (Or Not)

ELECTRIC: Running 20 feet of extension cords to a 1500-watt portable heater with blower fan doesn’t work well. Initially, I made the mistake of not using a heavy-duty extension cord, so the lightweight cords got so hot, after about 12 hours, that the rubber-like coating around the wire began to melt. Even after switching to a heavy-duty extension cord, the heater still did not run at full output; only about 1,190 watts on the 1,500-watt setting (checked with a meter) – the heater was struggling. This was in part due to the long, thick extension cord sucking up much of the electricity. The result was less than acceptable as it brought the temperature up only about 15 degrees; from low 40s to mid 50s. Survivable for sure (with the right clothing, blankets, etc.), but one must expect the power will go out in a serious emergency, especially a nuclear one. A solar-powered system wouldn’t be an option either with its computer-controlled inverters and voltage converters as it would get fried in an EMP (electromagnetic pulse). Also, there would be no real safe way to go outside, due to radiation levels, to keep filling up a small generator or fixing a high-fuel-capacity diesel generator if it stopped running. I would never be able to store enough fuel and gas stations would be empty anyways. Next.

PROPANE: There are a lot of propane units out there and the one of the most popular is the Mr. Heater Buddy model. It uses small propane cans which every Walmart carries and is a great heater, but not for a closed in space. All shelters of this type should have a filtered air ventilation system, and I’m working on one. However, I wanted to test the “Buddy” out with everything closed up in order to get a baseline as to the carbon monoxide (CO) output. Now, these heaters are designed for low CO emission and people do use them indoors, but this is a 12’x24’ space with a seven-foot-high ceiling. The result was that after an hour, the space only went up two degrees and the CO emission was 21 ppm. I have a touch of asthma and although this is considered not to be a very high reading, my lungs detected the change as it became a bit harder to breathe although, my girlfriend and her older son did not notice. The levels would rise and eventually reach the danger zone. For example, nine ppm of CO is the maximum safe level for eight hours, and 200 ppm of CO is fatal in a couple of hours. Most modern propane heaters have a shut off switch if the CO reaches a dangerous level. That’s great, but not having heat puts you back at square one. Onward.

BODY HEAT: Yes, this is a thing within a small space with concrete walls. An adult male body will generate about 120 watts of heat (or about 250 BTUs) as long as the daily calorie intake is over 2,500. So, if enough people are in the shelter, body heat will bring the temperature up quite a bit. Another effect is that if the walls are made of concrete, the concrete will actually absorb body heat in a couple of days and start reflecting it back! However, this is not a reliable heat source. For one, I don’t want a bunch of people in here since that will sink my “lifeboat” (watch The Twilight Zone episode The Shelter), and I’m not even calculating carbon dioxide which would be expelled by every human in here. What if I wind up single in the future with no one to save but me? Just my body heat won’t be enough. Plus, the math to figure all of this out is not something I’m interested in. Moving on.

WOOD: A wood burner would be great for a few reasons. First, this isn’t Phoenix, Arizona – I have woods with enough trees to heat my whole house for the next 1,000 years. So, fuel is no issue, just the work to get it cut. Second, I can cook over a wood burner, as well as boil parasites out of water. Third, heat from a wood burner can put out more than enough warmth. Drum roll please…

Say “hello” to my little friend!

Enter the Cubic Mini Wood Stove. Being a YouTube junkie for anything about RVs and camping, I watched dozens of videos about these little square fireplaces for many years. Cubic Mini Stoves began showing up not only in tiny homes, boats, and small cabins, but also in RVs, especially do-it-yourself RV builds like converted school busses and U-Haul trucks. Thousands have used these little fireplaces in small, closed spaces on wheels without issue – my quest for a safe heater is over!

There are two models available: the Cub and the Grizzly Cubic Mini Stove. Having watched a lot of videos on these, I knew that the Cub was suited better for spaces under 200 square feet. Also, since the Cub is smaller, it needs to be fed wood more often as time to burn up the small load of wood, and future hot coals, is about three hours. So, to get you through the night, you will have to wake up in the middle of the night and put more wood in (not an issue if you are a guy past 45). If you have more space, up to 400 square feet, then the Grizzly, model CB-1210, is what you seek and that was my pick. Another advantage here is that the larger model Grizzly only needs to be “fed” about every five to seven hours depending on how you are adjusting your burn.

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This larger model measures in at only 11”x12”x10.5 inches, is constructed from 1/8” to 3/16” steel plate and produces 8,000 to 18,000 BTUs! That is the equivalent to 2,346 to 5,279 watts! There is no way I could get that level of heat from an electric heater after “the big one” goes off, and even in “peacetime” a heater with that output would require a 220v line long term. It also has a secondary combustion system which means that it pulls air from one air intake and mixes it with the wood gas (which is also flammable) and this keeps igniting the wood. Great design!

Although my space is just under 300 sq. ft., I have a much higher ceiling than a boat or small RV. Yes, ceiling height matters and when you order a stove from this company, and they have a fantastic, automated form to fill out online which asks a bunch of questions about the space you want heat. When you are done, it will recommend not only which model is suited for you but also how much stove pipe will be needed as well as any other parts such as wall heat reflectors, flue system, mounting brackets, etc.. I’m not going into every step regarding the install as my “space” is unique (and there’s an instruction manual available), but I will go over some of the highlights from my installation.

Getting Started

When my Grizzly arrived, I will say that the packaging is superb; all parts, including the 34-pound stove, were packed professionally to make the journey from Quebec, Canada to my front door. For my build, I received: seven sections of three-inch stainless steel double-wall pipe (six 24-inch sections, one 12-inch section), one five-inch diameter 24-inch long insulated pipe, four heat shields, wall mount, chimney roof flashing kit, fire bricks, hardware, fireplace kit, and a heat-activated electric fan. Now understand, each “package” is custom and what you get is not going to be what you see here – you may get more, you may get less depending on the type of space you want to heat. As you will read, I have a lot of leftover parts with my unique space as I didn’t know exactly what I was getting into. I also wanted to have a second location for the stove since it is small enough to be moved easily. First, I installed the legs on the Grizzly; if you plan to just wall mount it, you may not need these. The next step was to peel the protective plastic from the double-wall pipe. I figured on two 24-inch section to get the pipe up to my ceiling. Okay, now for the complexities of my install which you probably won’t have. Whoever built this root cellar-type room added a vent pipe which is going to be used as a chimney. Since there are a few of these, which were installed to circulate air and prevent mold growing on food, I can sacrifice one. My idea is to get the double-wall pipe just inside the existing pipe and couple it with a reducer which will go from three-inch diameter to four-inch inside diameter pipe. This way, I can use the existing air vent pipe as the rest of the chimney. Now that I have a plan, on to the next step.

Before the Grizzly and the double-wall pipes are installed, the Grizzly must burn for several hours, and this can’t be done in your space. Why? Because the high-temperature paint on stove must be cured, and during this process, the paint will off-gas some nasty fumes. So outside, I prepped the stove by installing the fire bricks (these help insulate the fireplace walls from the heat), You will also notice in the photo the rope insulation around the thick glass window – just like any indoor fireplace. The next step is to connect the double-wall stovepipe. Don’t drink a lot of coffee while putting pipes together as this step sucks and is very frustrating. My first attempt to connect two pipes took 45 minutes. After watching a YouTube video from this company, I managed to learn a little trick. Some went together a little easier, but most do not – we are dealing with sheet metal here not precision-machined parts. After getting two sections together, I topped it off with the stovepipe rain cap/spark arrester. Now, I have to feed this bear. The wood from my woodpile will not work as its too big, so I got out a chainsaw and cut a fireplace log into pieces no more than about 6 ½ inches long (I split them a couple of more times as well). Once cut, I put in a piece of fireplace log starter and the dried wood. Soon the smell of cherry wood filled the air...along with paint fumes. Since I was outside, the fume issue was not a big deal, and I was enjoying the sight of beautiful orange flames. After about 10 hours of burn time (over a two-day period), I felt that the paint was cured as much as it was going to be.

The Install

My first issue was that the hole in the ceiling was too far away from the wall which I was going to mount the Grizzly. (And using some sort of elbow pipe was a bad idea in my option.) This was an advantage in one way, and a disadvantage in another. Bad news first. With new installs, most require cutting new holes in the roofs of their RVs or tiny cabins, not using an existing hole. Because I could not use the wall mount, I would have to make a platform or table that the Grizzly could sit on. The good news was that I didn’t have to cut out a ceiling hole, install any of the flashing kit, install the wall mount, install the wall-mounted heat reflectors, or use the five-inch diameter insulated pipe. I could save all of these parts for a second location which would be my dream RV!

The company’s representative did mention that the stove should be placed as close to the floor as possible as this would ensure a better distribution of heat. Since I do plan to use it for emergency cooking, I placed the cooktop area at 42 inches from the floor. I then came up with a simple design for the table using 4x4s, plywood, a 12”x12” piece of ceramic tile (as an insulator), and some adjustable table leg “feet”. The reason I wanted the legs to be adjustable is because the stovepipe crimped coupler end should be fully connected to additional piping and to the stove. By lowering the “feet”, I can separate the pipes and lower the table to remove the fireplace. If you decide to go this route, you now know which parts you can eliminate from your order.

After installing two sections of double-wall pipe into the hole of the ceiling, using a modified four-inch to three-inch sheet metal pipe reducer, I proceeded outside to install the rain guard/spark arrester. [NOTE: the one 24-inch piece of insulated pipe, which has a five-inch diameter, is not needed because the vent pipe in the ceiling is surrounded by concrete and soil and not through a roof made of flammable material like wood, or plastic, or shingles. Thus, no risk of fire.] A couple of weeks earlier, I realized that the stovepipe rain cap/spark arrester provided would only work with the pipes provided, and not with the existing air vent pipe on the root cellar. So, I went to a local hardware store and bought a stovepipe rain cap, but it had no spark arrester. A spark arrester is really just some “chicken wire”-type screening which looks like window screening except that the squares are much larger. I bought a roll of this screening, cut it with tin snips, and installed it in the rain cap – it looked like the big brother to the one I got with the Grizzly. This screening catches burning embers to prevent outside fires. The rain cap/spark arrester was then installed, and I was ready to light it up.

Houston, we have a problem

Anxious to get things going I, I put some wood in along with a few charcoal briquets and squirted on some charcoal lighter fluid. Once the fire started, smoke stared to pour in. I tried to adjust the air intakes, but that wasn’t the issue. My idea to use the existing pipe caused cold air to rush down, cool the smoke and send it pouring down. The double-walled pipe would have to run all the way through to the top of the vent pipe. Also, NEVER use any charcoal fluid or any type of liquid combustible in this fireplace. First, the instructions say not to and second, my room got filled with lighter fluid fumes. Learn from my error. So, I had to take everything apart and connect more sections of double-walled pipe. Did I say how I hate doing this? (I would like a few minutes in a boxing ring with the guy who designed this pipe.) After 30 minutes of frustration, I decided to take some tin snips and cut the inner crimped pipe so that it could funnel in. This is stainless steel and not aluminum so that didn’t work, but I was able to bend the inner pipe toward the center for the same effect. Eureka! It worked! They went slid in like butter, yet held firm. After the stovepipe reach the top of the vent pipe outside, I was able to “rig” the rain cap/spark arrestor on top, but I had to use the original one this time as this was now a different set up.

I loaded the Grizzly up with some cherry and other hardwoods at it the fire using wood shavings from the cutting. Wood size was about six inches in length and 10-12 inches in diameter. The primary draft/air intake is opened all the way and controls the speed of the burn, while the secondary draft/air intake allows air to be mixed with the wood gasses to reignite the wood continuously. When starting the fire, keep the secondary closed until it has a good burn. I did “play” with the primary air intake (opened about halfway) to get the right burn I wanted which was about a medium speed.The room temperature started at 53 degrees Fahrenheit, and the carbon monoxide (CO) level was zero. After one hour, the immediate area noticeably warmed up (within 10 feet) but halfway across the room it was only 56. The second hour was about the same at the halfway mark, but the area within 10 feet of the stove was warmer than before. Also, the CO level was still at zero which was comforting. I decided to load more wood and increase the burn speed which would raise the heat output. At hour three, I measure the temperature within 10 feet of the stove, and it was 72. Moving heat through a big room like this only requires people walking around or getting a large piece of carboard and fanning it about six times. The fan which generates electricity from heat, helped to move the warm air around the room continuously (buy one) – “set it and forget it”. As you can imagine, this room has humidity – a wood burner removes it so it will double-duty as a dehumidifier.

However, there was a bluish haze in the room, and it smelled of strong paint fumes – it seems I did not do a good job of curing the paint. I would have to stop the test and turn on an exhaust vent pipe fan to pump the fumes outside. Had I continued the burn (without this issue), the whole room would have heated up in time. Will this work for my nuclear bomb survival purpose? The jury is still out. Sure, the Grizzly is awesome and heats my space. However, for a nuclear, biological, or chemical attack, the shelter must be “buttoned up”. I will have to have “blast valves” installed on all air intakes and exhausts (available from American Safe Room, AmericanSafeRoom.com). What these do is immediately close when bomb overpressure is reached so that you are not injured by the blast effects. The other issue is that radioactive particles, pathogens, and chemicals could travel from your external stovepipe down to your stove thus exposing you. I will have to get back to you on this.

Did I mention that once installed the Grizzly can be moved to another dwelling or vehicle? If you want to move your Cubic stove from your small hunting cabin to your RV, you can. Just do another install and you can move it to wherever you want it. Remember RV owners, if you get stock in winter weather, and your propane is out and your generator is not working (or out of gas), your RV is a deathtrap without heat. Everything I received was high quality. About 15 years ago, I had a very good quality wood burner fireplace installed made by Bliss manufacturing, the cost was almost $9,000. Bliss is very respected in the fireplace industry, and I will say that the Grizzly Cubic Mini Wood Stove is every bit on the same quality level. But the Grizzly won’t set you back $9,000 for this mini fireplace and install. Currently, this Grizzly has an MSRP of $617 and you can install it yourself. They even have water heater and bread oven accessories! Go to CubicMiniWoodStoves.com to get yours.

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This article was originally published in Be Ready! magazine. You can find an original copy at OSGnewsstand.com. If you have any thoughts or comments on this article, we’d love to hear them. Email us at FirearmsNews@Outdoorsg.com.