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.
Replies
Please, do a LOT more research before going forward with this. Follow local codes. Have it inspected. Buy extra insurance.
I wouldn't do it in a million years.
Mini splits are great. Much more heat, plus AC and dehumidify. Cheap to run. Won't burn down your house.
I would strongly recommend an alternative heating source.
Since you ask, most wood stoves come with instructions. I have two in my home - both professionally fitted - and they have specific fittings for where they pass through the ceiling which ensures the flue is kept separate from the potentially flammable surroundings.
You can usually put the stove closer to a non-flammable surface, but it's not much. A properly designed stove won't put out much heat at the back and sides - most comes out the front and top.
If you were considering a home-made option, you should also bear in mind that they are horribly inefficient, and waste a lot of the wood thrown in them.
As you have free wood, the heater does make economic sense, but I'd still go for a heat pump.
Agree with the other posts. This is not a job for amateurs. You want to have a 90 degree bend in the flue? Wood burning stoves creates creosote, especially if you control air input for burning rate. I presume you will have 4" flue, you will have to get the clean out brush around the bend. Don't want to clean out creosote? Well you don't want a chimney fire do you? Triple wall pipe above the roof and high enough for local codes. I ran ours for many years until it got to be too much work and replaced it with a pellet stove, much less maintenance. In my shop I have a mobile home furnace, runs on propane. I have good insulation, probably only use 100-125 gallons a year, heats up quick, almost no maintenance.
Many alarm bells here. "cheapest way" "Frankenstein" "90°" + "1/2" plywood" all add up to a fire IMO.
Free firewood is my favorite kind, build a nice firepit a safe distance from the shop (and house) and go with a mini-split.
All excellent advise above. Don't ever try to jury rig your chimney. Even if you don't have a fire, you may get the silent killer, carbon monoxide. At the very least you'll probably need cement board behind the stove, and an air space between that and the plywood wall.
I heat my house with wood, with the exception of a small wall heater in the bathroom that's all I use ,but not in my shop! I was involved years ago with a woodshop in an old farmhouse. Heated with wood eventually it burned down. A new shop was built "fireproof " construction, semi solar heated and it did have a woodstove -but state of the art ,masonry wall behind , masonry hearth, masonry flue. It was a beautiful shop! 40 years later it burned down! Neither fire was on my watch.
It makes sense, right?, woodshop scraps plenty of kindling, cheap to run. Sounds practical!
Why it doesn't work: for certain operations you need a consistent temperature. Gluing, finishing. Maintaining a constant temperature( warm ) for say 24 hours( read the back of the can) means maintaining a fire that long. That's a fire going while your not there. Reading the back of the can, you know those open flame warnings? Hummm!
Your somewhere that freezes? Not maintaining above freezing in your shop will kill things like glue,and many finishing products.
Your shop is only 400 sg. ft. A small electric space heater will easily heat your shop. I tried one of those Mr. Heat propane heaters but discovered that a by product of burning propane is water and the humidity in my shop went to unacceptable levels so I switched to a infrared ceiling mount heater that works quite well.
Another story: A flue story. I lived once upon a time in a cabin in the mountains. I had one of those Ashley woodstoves and a masonry flue. You can shut those things down so that it smolders away and being spring that what I was doing. One fill up and it could take a day or more to burn. One middle of the night I woke up to this incredible noise,like an f16 taking off! It was the woodstove and a chimney fire! I went outside and there were 20' flames blasting out of the chimney! Inside the white hot stove was huffing and puffing and the pressure imploded the stove! It ended up looking like a dressmakers manikin! A metal flue would not have survived that and I would have burned up in my sleep! So, the bit about cheaping out on the flue.....
I'd suggest plenty good, not those Walmart versions, fire extinguishers!
Ok. Now I'll never sleep again in my old farm house with a wood stove (we tend it religiously).
I agree though. I have a 400 sq ft shop. In the morning I run my propane fireplace for about half an hour to get it up to a workable temp for the day. The rest of the time I let a space heater keep it around 50. Not ideal, but it's what I have.
Oh, where y'all getting the money for these minisplits?!?!?
I have an addition that had electric baseboard heat. Several years ago it cost 550 bucks a month to heat, just during the day.
I bought an 18,000 but minisplit, learned how to install it, and did it myself. It was 1,400 bucks, including the couple of specialty tools I lacked. It's really not difficult at all, and it's fun learning new things. I've done two more since then.
It was actually money in my pocket before the first winter was over.
Fear not Ben. I've heated my 200 year old farmhouse for 20 years with a wood furnace and have two fireplace mounted wood stoves that we've always used for supplemental heat when it's cold enough to want heat but not cold enough to fire up the furnace. All are masonry flues into which I installed stainless steel liners. Many of my neighbors heat with wood stoves and have done so safely for decades. Keep your chimney clean, burn dry hardwoods, and be smart.
My rule of thumb (and it's the one that came with the instructions for the furnace and stoves), make sure to get the wood stove and chimney good and hot before letting the temperature drop. And did I mention keep your chimney clean? :)
FWIW, I tried heating my shop (~2000 square feet 1 1/2 stories) with wood. Eventually gave up and went with radiant propane which I love.
Hey Ben! The mini-splits are pretty cheap these days, at least in Canada. There also several grant programs in place to encourage people to retire old furnaces and replace them with split-units. For my Shop (710 SQft) I use a mini-split. I got mine through a rental program. No up front cost, install included. I pay a very small amount each month, and I barely notice the electricity cost it adds to the bill. I recommend looking into it. There is likely something in your area that also makes sense. You have 100A out to your shop if I recall. Mine only needs 15A at 240V.
Hi Ben,
I paid through the nose for mine. The two things that made it less painful was saving up and paying "cash" for it and secondly, when it's near tripple digits outside, I am in my shop in the mid to low 70s and happy.
Sincerely,
Joe
Hey, I just wanted to let everyone know that I really appreciate the discussion on mini-splits. I have a 400 sqft woodshop (garage, but no cars allowed) that I air conditioned and heated day and night for 27 years with a wood stove. I just had the concrete floor replaced and had every intention of buying a new wood stove. Well, I bit the bullet on a mini-split and so far, could not be happier. I still need to cut and split wood for our fireplace insert (upstairs) and wood stove in the family room (downstairs), but the stove in the shop consumed most of the firewood. At 70 I figure I can cut back a little now.
Lol. My father used to love to split firewood for his fireplace in the living room that he used a lot over 50+ years in that home. He started to slow down at splitting the wood in his 70s as well.
All very good advice, that. But there are two major problems with wood stoves nevertheless ....
The first is that keeping the chimney and stove very hot internally does stop tars forming in the chimney, which tars are often the stuff starting fires via secondary ignition in the chimney. But so-insulating also reduces the heat put out into the room; and throws away enormous amounts of heat up the chimney and off to elsewhere.
This amplifies the second problem, which is that a wood stove creates enormous amounts of greenhouse gas and micro-particle pollution. Each woodstove, it will be claimed, is a small matter. But when there are millions of them nationwide because it's less expensive (in cash terms at least) than other heating methods means that each stove is part of a very big problem.
Those highly damaging particulates, by the way, are not just a problem for your neighbours. The small particle pollution inside a room with a wood burning stove is far greater than it creates outside. The smaller inner space concentrates them before putting them into your lungs & elsewhere about your body, where they slowly kill you.
*******
Greener and cleaner alternatives are expensive. But then so are all household gubbins performing major tasks. Moreover, electricity supply and it's vulnerability to worsening weather, as well as commercial collapses of suppliers, means that you can invest in solar panels, heat pumps, batteries and the like and (despite the hoots of various oil&gas lovers) get your money back in a decade to a decade and a half .... whilst having some resilience from grid outages after weather and/or commercial trashings of the supply.
We've done that in our house. Currently we generate more electricity than we need over the year and also manage to get around £1000 back from the suppliers for that excess over and above what we pay them for grid electricity during low sunshine days (loaded and stored overnight in the batteries at a price 1/3rd the day rate).
Since the house and car are all electric, the green gubbins saves us £4000 a year in electricity costs (currently; it'll be more each year). This saving will pay for the gubbins in 10 years or less.
The woodworking shed is integral to the house (a built-in garage) and gets insulated/heated just like the house. But you could connect a safer and cleaner electric heater to you electricity supply even if the shed is a goodly distance from the house. Perhaps it's a handy place for some solar panels; or even a windmill!
In CA, we have high costs for electricity and gas. If I had to average across 12 months, I'm likely at least at $400 a month. A back of the envelope calculation had solar on the roof at $30K (likely has dropped since I looked). Payback is under 10 years for me. Now just trying to sort out if we plan to live here long term when we retire.
There's no doubt that the purchase and use of modern solar panels, inverter and storage batteries can save you a lot in electricity bills. Add a small box that allows you to continue using your solar & batteries when the grid goes down, after the next bad storm or the supplier goes bust, and you can keep the light & heat on too, when everyone without such stuff is in the dark and cold.
The difficulty is the capital outlay - rather like the difficulty when wanting large and good quality woodworking machinery. :-)
But, if you can find that capital to buy the solar et al, you will get your money back in around one decade. If you come to sell your house before then, its slowly becoming the case that solar/battery installations can certainly make a house more sellable; and may also increase the viable asking price.
In all events, as well as getting your power for nowt, you also create less/zero pollutions of many kinds. There's still lithium mining and other gubbins-manufacturing environmental costs but they're far, far less than those of oil, gas and wood-burning technologies.
**********
At the beginning of this year, we added a 4k array, inverter and three 10KwHr (30 in total) batteries to an already extant 4k array. It cost £28,000 for everything including the installation. (Solar Edge technologies). After 9 months of use over winter-spring-summer, it's already reduced our electricity spend for that period to near zero.
The colder & darker months will see an increased draw from the grid - but at around 1/3rd the standard cost per KwHr as we draw cheaper overnight power to store in the batteries for use the next day.
One thing to look out for is a sell-to-the-grid contract with your supplier. In the longer and sunnier days, you generate too much electricity to use & store yourself. A good contracted price for selling the excess produced to your supplier will be another plus in the accounting balance of the system and its use.
Thanks for the specific details. At some point over the last decade, I have made the decision that for just about everything, I either pay fully for it or I wait or I do without. It certainly does slow things down in terms of what I can buy but I own it. I absolutely hate debt. Never was going to loose a house over debt but still stressed me out.
The emerging consensus seems to be that you should avoid burning stuff in places where people are. This seems to apply for space and water heating as well as cooking. Soot/particulates, carbon monoxide, and volatile compounds such as benzene all seem to be in play. There’s likely much more info on this at Fine Homebuilding for those who are interested.
Find one of these in good shape and go for it. It is efficient and safe and will keep your shop warm.
I'm going to be the contrarian here. But, then again I'm an old man and hobby worked in wood and coal heated shops for probably 20 years up 'til the early '90s. Wood heat can be safe and economical. It's a great way to dispose of those pesky endcuts that seem to accumulate around the shop.
So comments regarding your post. If you go with wood, please consult with a pro... or at least someone who's done it successfully for a period of time. For example, I don't believe you want your stack running through 1/2 inch plywood. You'll need to insure the plywood "behind" the stove is a safe distance and that it's insulated and fire retardant. You don't need much of a stove size wise to heat 400 sq. ft. In fact even the smallest of stoves would run you out (temperature wise,) on a cold, cold day with a strong fire.
Learn to manage the fire, safely. Use top quality insulated stack. A 90* bend isn't a big problem - it's done all the time, and often twice in the same run.
Check for a wood stove pro in your area and talk with them.
Warmest regards!
Creosote is a problem, but manageable if you use the driest woods and are cautious about the size of your fires.
In the house before the current abode, we had a garden room of cedar lined inside with plywood and insulation between the two. A small wood stove was installed to heat it in winter.
The woodstove was very small and sealed except for an airtight ash pan, a close fitting top lid and a small opening in the top beside the lid which was the only way air could get into the stove.
This stove was advertised as highly controllable and without any open fire ever being exposed to the room. The air inlet was a sloped vertical pipe going down to the bottom of the stove inside it's body, to under the grate. It had a fine air inlet controller on the top which would actually extinguish the fire if fully closed.
The vertical air inlet also meant that it was safe to burn sawdust and shavings, which are normally regarded as a potentially explosive risk in ordinary wood burners. Wood, sawdust and shaving were fed into the top plate of the stove, with the burn always at the bottom, slowly consuming the burnables at the required rate via control of the air supply.
The thing nevertheless burned hot and clean if the wood et al was dry (which it was from the offcut basket of the woodworking shed). The chimney was a double-insulated metal edifice that could be hand-touched when the stove was going full blast. Nevertheless, it was surrounded by fireboard rather than the plywood of the rest of the internal walls.
*******
As you say, get expert advice. Ordinary wood stoves are a risk in wooden buildings because they have exposed very hot parts and an exposed fire, both when loaded with wood and as part of the design to produce radiant heat direct from the burn. It only takes one glowing ember ejected unnoticed into a wooden building and it can consume the whole edifice in no time.
When setting up a wood stove in your small shop, safety is paramount. You'll need clearance from combustible materials like the plywood wall. Typically, a minimum clearance of 18 inches is recommended, but it can vary depending on the stove model and local regulations. A sheet of corrugated metal roofing can add extra protection.
To connect the exhaust pipes and ensure good updraft, use stovepipe sections and elbow joints designed for wood stoves. The length of the pipe depends on your installation and should provide a proper draft.
For a small shop, a compact wood stove with a length of around 20-30 inches should suffice. Consult local experts or authorities for specific advice on your setup. Regular chimney cleaning and proper venting are crucial for safety.
As the weather gets colder I'm worried for Bradley's well being. It would be nice to hear from him one last time.
Free firewood is my favorite kind, build a nice firepit a safe distance from the shop (and house) and go with a mini-split.
Here's a summary of a study into the relationship between indoor wood burning for heating and the incidence of lung cancer. A sobering piece of information for those using a woodburner.
https://www.sciencedirect.com/science/article/pii/S0160412023004014?via%3Dihub
Lung cancer is unlikely to be the only human ailment exacerbated by wood burning gases and particulates.
Lataxe
I know little about wood stoves, but had an experience 40 years ago that left an impression. Three of us were returning from a hunting trip in the N GA mountains, tracking wild boar in the snow - with pistols . Picture us, dirty and dressed in wet hunting gear, with empty shoulder holsters, the .44 mag pistols in the car trunk.
As we neared home, something caught my eye at a house on a side street to the right. There were flames shooting 15 feet out the stovepipe, and large sparks landing on the roof. I turned into the driveway and we pounded on the door.
The door opened with a lady standing in shock and I'm yelling that their roof is on fire. I looked to the left and in the next room was a wood stove, glowing red hot, as was the stovepipe, and I do mean bright red. I pushed her out of the way and ran to the stove, and was trying to close the damper with a piece of wood. Somebody yelled to look out, and I turned and her husband was coming with a pan of water to throw on it. I managed to block him and the water went everywhere.
Meanwhile, Ken was yelling about we needed to check the attic, and Dave was yelling about fire on the roof and we needed a ladder. Several kids are screaming.
Complete pandemonium. Had he thrown the water on the hot stove it would have shattered and it would really have been a disaster.
Bottom line, the stove cooled quickly after the air was shut off. No fire in the attic, some burned spots on the roof. We apologized profusely for disturbing their family dinner. They had been trying to get the new stove started all afternoon and had finally left it with the damper wide open, not visible from the dining room. I detected a faint odor of gasoline.
Fast forward a few weeks and I was to interview a lady for a job opening. In walked this lady. She recognized me and muttered that she didn't think she was interested and walked out.
Shop heating with wood/pellet stoves: Best better to check with your insurance agent. Some will provide coverage, others will not.
About 5 years ago I checked with several carriers about increasing my homeowner’s policy coverage and the coverage for my detached shop. Several asked if I had any type of wood/pellet burning stove or fireplace in the shop. If I did, they would decline coverage. Was told the same several years earlier when we first moved into the new house and shop.
All good opinions on this topic. I’ve heated my home with wood for 50 years, and my woodshop for 6-7 years. It was a 24’x24’ 2 story building with a concrete slab. The 6” stove pipe went up to a metalbestos chimney and through the metal roof. No creosote buildup, ever, but 2 things made me switch to a gas space heater, one, lightning hit the chimney while I was in the shop, and the stove jumped a few inches and turned 5-10°. Yikes! Two, the amount of space the stove took up, especially the big radius around it that I couldn’t use. I gained a lot of square footage.
Amen to the space that a wood stove takes up. I didn't realize how much until I removed it and had a mini-split installed. Huge improvement.