How to own a wood stove

[brad hays]

I'm gearing up my little 400 sq ft shop to be heated with a small wood stove this winter and thought I'd ask some advice since this will be my time first owning one. I think even a small stove would be enough for the shop, as I'll have a fan on it. I just need it to be long enough to take in unpredictable lengths of firewood. I've got a small log splitter so I can control the thickness you could say, just not the length. I've got a couple free sources of wood, just have to take it as is.

I'd like the top flue pipe to turn 90 deg parallel to the floor very soon after exiting the top, and then exit through a 1/2" sheet of plywood that serves as the wall behind it.

First, what kind of clearance do I need to keep away from the plywood wall it's nearest to and exiting through?
Can I put the stove closer to that plywood wall if I put a sheet of say corrugated metal roofing between it and the wall?
What's the cheapest way to frankenstein my exhaust pipes together, including the through wall piece?
Does the pipe needs to be a certain length in order to create a good updraft?
What size stove should I look for, length wise?
And lastly, any and all extra advice appreciated.

[Kevin Jenness]

Check your local fire regs. 18" clearance to combustibles with a metal shield spaced off the wall, 36" without. Insulated metal shield over a wood floor. Use metalbestos insulated pipe through the wall with 2" clearance and a wall flange, a tee with a cleanout at the bottom supported on a wall bracket and enough vertical metalbestos pipe to reach 2' above the roof with a cap on top. Get a chainsaw to cut firewood to length or use a bandsaw. Use dry wood, don't let the fire smolder and keep the chimney clean. Have a fire extinguisher on hand or at least a couple buckets of sand. Make sure your insurance is ok with wood heat. Consider a heat pump (mini-split) as an alternative.

[Scott Winners]

First you need to pick your contenders, then you need to read their manuals, typically available on line for new reputable stuff. Even the really inexpensive stuff like at team blue and team orange homestores are reputable enough to have online specs for clearances to combustibles. Sidewall of stove to nearest combustible, rear wall of stove to nearest combustible, minimum flue heights, that sort of thing.

I am burning 6-8 cords annually in a 2400 sqft house in Fairbanks, Alaska, in a very modern woodstove that would be much too big for your shop. You do need to put on your green accountant's visor and look at the insulation and air leaks in your shop as if you don't own it yet. Air leaks cost BIG BIG money, at least up here. Remember a small slow leak can sink a great ship. If you can feel cold air coming through the wall, around windows, receptacles and light switches on the exterior walls, those are costing you money every minute you are heating the place, no matter what fuel you are using for heat. Electric, natural gas, cord wood, doesn't matter, air leaks are costing you money.

I cannot think of a single stove that will work well with a 90 degree elbow in the flue pipe within 48" of the stove top. Sort of like having a section of straight pipe coming into the cyclone on your dust collector, you (we, I) really need predictable airflow for the equipment to run dependably. If you really really MUST install a through the wall flue, a better choice is the tallest pipe possible coming up off the stove, then a pair of 45 degree elbows also with straight pipe between them and then heading to the wall exit. This is a suboptimal installation and will be a bugger to keep clean.

I fully recognize folks down south can "get away with" a lot of compromises in stove installation down there that are simply unacceptable up here. I used to fell my own trees and buck my own logs and bring the rounds home in my truck and then split and then stack, it is a LOT of work to pull 200 million BTUs off the stump every year. And my install and system is adequate to keep my homeowner's policy in force in case of a fire.

You literally asked "What is the cheapest way to frankenstein my exhaust pipes together?" I am really making an effort to stick to the "be nice" guidance that is supposed to guide all our posts on this website, but realistically you are asking for guidance on how to set your shop up for a total loss in event of a nearly inevitable fire.

If you truly own even two tools that you really like from good brands we all have heard of; I think your time and money will be better spent on sealing air leaks and improving your insulation. Or take your tools into the house, burn the old shed down now, and build something with good insulation and good air sealing to put your tools back into.

[Scott Winners]

Make sure your insurance is ok with wood heat. Consider a heat pump (mini-split) as an alternative.

Both awesome ideas. I haven't lived in KY since the 1980s, but I remember it was hot and humid a lot longer than it was cold and dry. A minisplit could be brilliant if airleaks are minimized and insulation is not very thick at all by Alaska standards.

[Zachary Hoyt]

I heat my shop with a small wood stove in the Adirondacks, which is a much colder area than yours. My shop is 15x31 on the inside with a ceiling height from 8 to 11 feet or so. As has been said above stove manuals will give you clearances. The best chimney path is straight up from the stove outlet through the roof. Lowes sells a Class A metal chimney line that's pretty good, and not too expensive. When I put the chimney in the shop I bought a kit with the flashing, hanger, cap etc for about $150 and each 3 foot piece of double wall pipe was around $100. I used 3 on the workshop so it was about $500 with tax and all. I have a similar setup in the house but it has 22 feet of chimney instead of 9. You can shorten firewood using many kinds of saw, and I don't think there is a small stove that takes long wood. Mine are both 18" max, 16" preferred. I bought the stove in the shop used for $500 and the one in the house new for $950 or so. They're both about the same size. I wouldn't want a bigger stove in a small space, as it gets harder to keep from overheating the space.

[Tom M King]

Without a chainsaw and ability to sharpen a chain, and a stand of firewood, I would suggest a mini-split. I have plenty of the above, and I would still choose the mini-split.

[Bill Howatt]

If you are buying used, make sure that all components like stove, chimney, whatever are (still) approved. My neighbor ran into this problem when he tried to set one up in his shop/garage. The metal chimney had been OK years ago but was no longer allowed to be installed. His insurance company didn't like his stove, for some reason, so the whole project didn't happen. You have to contend with the rules in your municipality and the rules of your insurance company.

[Jack Frederick]

Back 50 yrs or so I had a stove shop. I also represented Selkirk, Dura-vent and Z-Flex for about 20 yrs. Wood heat is a hobby. A nice hobby if you choose. I lived in a yurt outside Ithaca, NY for 2.5 yrs with no power, no running water, well the creek, a beauty of an outhouse and a half mi walk to the vehicle in the winter. Wood heat is swell. In so many cases people look at a room and say they have plenty of space for a wood stove. By the time you figure the clearances (wall to stove or pipe 18”, can be reduced with shielding and clo$e clearance pipe, the body of the stove, hearth, pipe, etc, you end up doing a do-see-do with the stove every time you walk through the space. You could easily give up 10-15% of your shop to the stove. Prior to moving forward with any expenditure I suggest you draw all this on the floor and don’t forget wood storage. Wood is great heat, if your insurer will allow it, and in the insurance business today that is not a small matter. Check with your carrier. You can have a rear outlet stove or a top outlet. It is bad practice to come off the top with a 90. As much V rise as you can get helps establish proper draft. By the time you buy a stove, the class A pipe for it, the close clearance stove pipe you will be in this for about the same as you could buy a Rinnai EX-22 which you can install yourself in less than 3 hours. Propane or NG is your choice, but the vent comes with it. It has a programmable stat, takes out almost no room and has a modulating burner and blower. If it is heat you want that is the way to go. If you want the best year round system, get a mini-split. The other thing about wood is it is nice once everything is up to temp. All of you tools and the building are at ambient when the fire is out. It’s nice grabbing a 35* wrench, don’t you think Folks who frequent this site have a wood hobby, business or simply passion. Do you really want another wood hobby?

[Jim Becker]

I kinda think that Jack hit the nail with the hammer there. I had a woodstove at our old property and we ended up using it very infrequently and finally not at all. (it wasn't needed for heat but originally for emergency use, etc.) But it was a lot of work to "feed" and if you didn't use the "food" it spoiled after a bit. If it wasn't for the insurance implications, I might consider one of those tiny wood stoves for my shop to feed unwanted scraps to, but I'd still be reluctant to dedicate the required space for it and be constantly cleaning to insure that there was no flammable dust accumulating on things that get hot. I opted for a mini split, both at the old shop and here in the new shop. Super efficient and also provides cooling/dehumidification during the warm/hot weather, too. And by the time you figure in the cost for the wood stove, the required venting system (which is not inexpensive), the extra floor and wall treatments, etc., a mini split is attractive cost wise, too.

[Kevin Jenness]

I've heated both house and shop with wood for over 35 years. It's a chore and needs to be set up, run and maintained properly to be safe. It can make sense if you have access to free wood, and you can burn your mistakes. A few years ago we put in heat pumps and only burn about half as much wood (2 cords rather than 4). I don't miss ramping the shop up from 40 F on midwinter mornings, but it's nice to have a dependable heat source when the power goes out.

[brad hays]

Thank you so much for all the info. I knew I was at the very bottom of the learning curve on this one. I'm taking in everything.

Here's something I've been wondering about. So much of the heat from a stove fire goes out the pipe, and just putting a fan on the stove multiplies it's efficiency by possibly a magnitude. This means that small spaces like mine can actually be heated by MUCH smaller fires than are in even the smallest of stoves. Is there a way to build a fire that's much smaller. Tending it would be different. There would be smaller additions of fuel and added more frequently. Is that what these pellet stoves are I've been seeing advertised used?

[Scott Winners]

Thank you so much for all the info. I knew I was at the very bottom of the learning curve on this one. I'm taking in everything.

Here's something I've been wondering about. So much of the heat from a stove fire goes out the pipe, and just putting a fan on the stove multiplies it's efficiency by possibly a magnitude. This means that small spaces like mine can actually be heated by MUCH smaller fires than are in even the smallest of stoves. Is there a way to build a fire that's much smaller. Tending it would be different. There would be smaller additions of fuel and added more frequently. Is that what these pellet stoves are I've been seeing advertised used?

I kinda got this one. As a wood stove becomes more and more efficient putting BTUs into your shop, the smoke going up the chimney becomes cooler and cooler. I wouldn't want to go up on my roof and try to breathe my own chimney's smoke, it is still pretty hot, but much much cooler that even 20 years ago.

Both of my last two wood stoves were about nominal 3.0 cuft firebox size. On the 1999 build I could turn it to the lowest possible setting and get about an 8 hour burn with the probe on my exhaust stack showing 450-550 degrees F for the rising gasses in the flue pipe. On my current stove, a 2014 build, I can barely get the flue gasses up to 600dF running wide open, about a 4 hour burn, but I can also with the 2014 stove, turn it down to the lowest setting and get 16 hour burns with the flue gasses running +/- 300dF.

On your chimney, you can go out to the back yard and look for an exhaust plume that is either attached, or detached. With a detached plume, you can see a gap (with maybe mirage-y heat wave illusions in it), but the visible exhaust plume is a few inches away from your chimney mouth. In this mode, all the water in your exhaust stream is still a vapor. You are not accumulating creosote in this mode, because none of the water vapor in the stream is cool enough to condense until after it has exited your chimney pipe.

If you see visible smoke right at the mouth of our chimney, somewhere in the chimney column the exhaust gasses have cooled down to 212 dF, so the water vapor in the plume can start condensing on the pipe walls. Where you got wet pipe walls, carbon particles can stick, and now you are making creosote in your chimney.

In real life even the best tuned and vigilantly operated wood stove systems are going to accumulate some crud in the pipe every season. There is a bajillion variables. The most important one is for the operator of the stove to brush out the pipe often enough to know how often the pipe needs to be brushed out to minimize the risk of burning down the house.

With an open fireplace, think colonial America, you can rule of thumb expect 90% of the heat made by burning wood is going up the chimney - and you got to have some cold air coming in somewhere to replace the hot air going up the stack.

There is not really good current agreement within the woodstove industry/ community about how to best measure efficiency. The most common measures currently bandied about are the low heat value efficiency and the high heat value efficiency. It is kind of like EPA ratings of gas mileage. There is probably only one person in America actually getting the actual EPA rated gas mileage out of their vehicle, but the folks in big SUVs are getting less gas mileage than the folks in Prius'. When you are comparing two stoves, the LHV and HHV are worth looking at for the sake of relativity, but it is extremely unlikely you (or I) will actually achieve the published numbers in reality.

I look at how much motrin I am taking to keep Mrs. W happy as a measure of stove efficiency, and my current 2014 stove kicks the slats off my old 1999 stove.

I have looked at building a standalone shop up here and using a woodstove as a heat source, and it just isn't worth it. One condensation event where I got water on all my sharp edges could easily cost me an entire summer spent on rust abatement and resharpening. I am pretty good about keeping the house warm with the wood stove so Mrs. W doesn't complain about the cold, but sometimes I get home from work late, the wood stove has burnt out and the oil fired boiler is chugging away. The more $ you got tied up in your tooling, the more interested you are going to be in automated HVAC.

If a minisplit is really not going to work for you ( I would require substantial AC to consider living that far south), you might look at pellet stoves. The vast majority of pellet stoves with the highest efficiency are clustered around rated for 1800-2200 sqft. Outside that envelope efficiency is going to drop off. Wood pellets are more expensive than cordwood, and pellets don't grow on trees. However, typical install is a 4" holesaw through the wall (but not through a stud) and a short (like 48") vertical pipe outdoors.

So before we dive into combustors, lets review. An "order of magnitude" to a physicist, in this conversation, would refer to increasing efficiency by 10x. Given a colonial era open fireplace is +/- 10% efficient, an "order of magnitude" increase would require a wood stove to be 100% efficient. This is not a reasonable goal for a physicist. Were a stove 100% efficient, the outgoing flue gasses would be at room temperature and the chimney would have to be cleaned daily or even twice daily. We are going to use some energy, some heat, to get the combustion products up the chimney and out of the house.

So catalytic combustor equipped woodstoves, in the right circumstances, can be incredibly efficient.

Full disclosure, the VP/COO of Blaze King is Chris. He and I have each other on speed dial. We chat ehh, 3-4 times annually. My current stove is a Dec 2013 build Blaze King Ashford 30. Since then BK has come out with the 30.1 and the 30.2. BK corporate policy, written by Chris, allows one free beer from BK corporate to each BK owner (and their plus one) for life. Buy a second BK stove, no second free beer. The second time Chris wanted to buy me a beer he invited the Fairbanks BK dealer to join us for dinner so the second beer purchase for me would not show up on corporate's balance sheet, you would have to look at the local BK dealer's books to find that second purchase. I did order the most expensive beer on the menu both times. I have received $23-24 worth of free beer from BK in two separate pint glasses. I have not received a third free beer from BK, or any other renumeration. I did get a free BK hat from the local dealer, but I see those all over town, so not special or individualized. Having spilled, my next stove will be another Blaze King. BK stoves are a great fit up here, but I don't see designing (and certifying) a very small catalytic stove for 400sqft in Kentucky as something any stove manufacturer is ever going to break even on. The EPA certification process for a new design wood stove is about a million bucks.

OP Mr. Hays can look at the BK 24 series fireplace inserts, and the freestanding Boxer 25. All of the BK 24 and 25 series share the same firebox internals and ride around on the same EPA certification testing. The Boxer 25 would be a good choice for a new build 400sqft cabin in Fairbanks with 2x6 construction, small triple pane windows, outstanding insulation, owner accomplished absolute airtightness, at -50 to -60 Fahrenheit. If someone in KY or TN really needs that kind of BTU output, I am back at square one looking at insulation value and air leaks. And AC. Lots of AC. Tons and tons and tons of AC.

Sometime today another user pointed out the fire hazard of having sawdust laying around the shop, the wood stove loading door open, and (very likely) hot embers popping out of the firebox onto the shop floor. Not as dangerous as gasoline or toluene, but still unacceptably high risk for many. This is why I mostly work in hickory, white oak, american beech, and if I ever find it, apple. My shop scraps mostly go in my BBQ pits to cook food, not risk setting my shop on fire with an inefficient wood stove.

[Scott Winners]

Is there a way to build a fire that's much smaller.

Yup, catalytic stove. As above, I have been running a catalytic equipped stove for 9 winters now. Up here we see +80, +85 dF summertime routinely, and -35, -40 dF winter routinely. I personally have not noticed -50dF since Jan 2009, but I have a day job and don't spend my nights staring at the official thermometer at the airport.

With a catalytic stove, in the right season, I can turn my air intake, my throttle, down super low, so there is just enough air going into the stove to keep the wood in the firebox smoldering, about 600dF, to burn carbon. But not enough air to burn all the carbon right away, just enough air to keep the wood that is burning hot enough to ignite the adjacent wood in the fullness of time. This is a very smoky burn in the firebox, the glass gets all crusted over and you might look at my stove and think nothing was happening.

But all that smoke gets routed through my catalytic combustor. So even though the air in the firebox is at maybe 600dF and most of the walls of the stove will be even cooler, if you rest your hand directly over the combustor you will find very quickly that little brick of noble metals is sitting at 1400-1600 dF turning smoke into CO2. With thoughtful experienced fan usage I can distribute the heat coming off the combustor to ~1200 sqft of living space. As my weather gets colder I have to open my throttle and burn my loads down faster, but the combustor is still on the team turning unburnt smoke into CO2 for the chimney and BTUs for the house.

I do not know of a catalytic stove sized for 400sqft down in the middle latitudes, but the technology does work beautifully in cold climates.

[Bill Dufour]

The classic Russian stove burns small sticks in a very hot fire to warm up several tons of masonry. Then the fire is allowed to die out and the masonry radiates heat for hours. I guess it is similar to a pizza oven<br>
BILL D.<br>From the Fort Ross site.<br>https://programs.fortross.org/elp/co...ith_the_pechka

[Jim Becker]

Thank you so much for all the info. I knew I was at the very bottom of the learning curve on this one. I'm taking in everything.

Here's something I've been wondering about. So much of the heat from a stove fire goes out the pipe, and just putting a fan on the stove multiplies it's efficiency by possibly a magnitude. This means that small spaces like mine can actually be heated by MUCH smaller fires than are in even the smallest of stoves. Is there a way to build a fire that's much smaller. Tending it would be different. There would be smaller additions of fuel and added more frequently. Is that what these pellet stoves are I've been seeing advertised used?

The better wood stoves have a catalytic system which not only helps insure that the "bad stuff" is burned more efficiently, but they also slow things down so at least a little more heat stays in the room. That combined with a fan can help. If you get to really fancy, built in masonry setups (not gonna happen in a shop), the flue gasses are circulated through a loop or two within the construction so that more heat can be extracted from the flue gasses before they exit to the atmosphere. Bill eludes to a similar thing