Wood Stoves/Heating

[BlueBirdman]

I was in the wood stove/solar business for years, right up until the economy crashed in 2007/2008. My favorite jobs were for the off-grid folks, and I got a lot of referrals in that market.

I was always a stickler for safety and have a lot of knowledge in that area. I'm starting this thread to try and pool ideas and experiences for everyone who wants to heat their conversion with solid fuel.

[BlueBirdman]

The first thing I'll address is stove location. I saw this under discussion here: http://www.skoolie.net/forums/f13/ou...-no-10520.html and would like to add my two cents worth.

I have three thoughts regarding that discussion, and they apply to everyone who heats with wood:

First, INSULATE. I'm a big believer in energy efficiency as the best path to comfort. The most important surface to insulate is the roof, followed by the walls and finally the floor. You can't neglect any of these surfaces and still be comfortable.

Even if I was on a very tight budget, I'd still use closed-cell spray foam in the roof. Besides being the best R-value per inch where it matters most, it completely eliminates air infiltration, adds rigidity to the structure and really dampens outside noise. The up-front investment in good insulation will pay lifetime dividends in comfort and fuel savings. (The comfort aspect is year-round, too, so it slashes your air conditioning loads as well...)

Second thought: a centrally located stove is no guarantee of comfort. It should help, but because the bedroom area is rather closed off, plus the fact that it has a ton of outside surface area relative to its interior volume, I suspect that bedroom will still be chilly. Go to the link and look at the revised floor plan if you can't picture what I'm saying - I suspect you'll agree.

Third: it is quite easy to distribute heat evenly with small blowers, except that it doesn't work in the way one might first think: I do not, ever, try to circulate warm air!

Rather, I pull cool air from the furthest reaches (which in the linked thread would be the bedroom) and blow it directly onto or as close to the stove as possible. This causes the warm air mass to "ooze" all the way to the furthest parts of the house or bus, resulting in surprisingly even temps.

I haven't done this in a bus yet, but I know it works. I've been able to achieve very even temps throughout my own homes and also many clients homes using this method. For homes, I use insulated flexible ducting and inline blowers available at Home Depot, Lowes, etc.

For a bus, I'd use the exact same idea but find an efficient 12 volt inline blower, which could run directly off house batteries without running an inverter all night long. Putting the blower in the middle of the run of ducting minimizes blower noise.

Moving air in this way works wonders in keeping the area the stove is in from becoming uncomfortably hot, too. If you do it right, your comfort level should rival that of a well-built home.

In my own plans the wood stove is going right behind the driver's seat. I'll most likely have an attic in my raised roof, so I'll use a run of small diameter (4-5 inch??) flexible ducting up there. It will be inside the insulation envelope, so it doesn't need to be insulated.

If you don't plan on raising the roof, you could always run a duct underneath the bus, in which case I'd use insulated flex duct and protect it from the elements by running it inside some flexible stainless steel chimney liner.

At the very least, one could put a blower in the bedroom wall that pushes cool bedroom air into the "living room" where the stove is. That would draw warm air into the bedroom, and should work pretty well with the centrally located stove in the revised floor plan. You'd probably have some blower noise, but you'd be a lot warmer!

You could always regulate the blower with a thermostat, too.

[Kcklr74]

Thanks for that information!
I gather from it that if I do it right, it is possible to have the wood stove in the original location?

[BlueBirdman]

In a skoolie, space is obviously at a premium. While manufacturers don't do the testing or provide the measurements, I believe it is fairly easy to SAFELY install many wood stoves with extremely small clearances to combustibles.

The basic concept of heat shielding is called a "protected wall" and is addressed in NFPA 2.11 (National Fire Protection Act Section 2.11, which governs all solid fuel appliances). I put a lot of stock in this stuff, because the insurance industry drives NFPA standards based on real world claims experience. Basically, whenever a few houses burn down due to a particular issue, they try to raise the standards to prevent any more houses from burning down in the same way. This beats the heck out of theoretical BS from legislators all day long!

Any "protected wall" is combustible, and the insulated wall of a school bus is ABSOLUTELY a combustible wall, even if it is still covered with interior metal. To be safe, combustible walls must be protected by non-combustible shielding with air gaps for cooling. NFPA 2.11 specifies a 1" air gap between the shield and the combustible wall, and a 1" air gap at the bottom, top and sides of the shield to allow for convection cooling. If you follow this, any wood stove can be installed within 12" of a combustible surface using a single layer of heat shield.

A few modern wood stoves have a lot of built-in heat shielding and can be installed with perhaps just 10" of clearance to side walls with no additional shields. The only closer clearances I know of are a few marine stove manufacturers who have tested their specific stoves with much smaller clearances. (Marine wood stoves don't put out a lot of heat, but would be a viable choice if you insulate well.)

Most of the time with most other wood stoves, the best way to reduce clearances from 12" is to use two layers of heat shielding. No accepted testing agency has experimented with this, so anything we do to install a stove with less than 12" of clearance is at our own risk.

I have played a little with two layers of heat shielding, Here's what I've come up with: First, I use metal with low thermal conductivity. That means stainless steel. I follow NFPA 2.11 and use another 1" gap between the first and second layer of shielding. The shield closest to the stove is bare metal, while the shield nearest the wall is backed with a 1/2" layer of Micore flame resistant insulating board. I keep a 1" gap between the Micore board and the wall.

For the non-combustible floor (the "hearth pad") I use two layers of Micore board under a single layer of stainless steel. This addresses the threat of radiant heat igniting flooring, which has happened more often than you'd suspect. No air gaps are needed, and I stick with the stove manufacturer's suggestions for hearth dimensions.

You MUST test this concept in each specific installation. I use a laser thermometer to test, and burn a hot fire for several hours on a cool day to get realistic readings. I shoot for less than 70 degrees Fahrenheit difference between ambient air and combustible wall surface temp. That will determine how close the stove can be to the wall. I would keep that thermometer around, and keep taking measurements in my bus under actual use until I was sure everything worked well.

Use double wall connector pipe between the stove and the ceiling, and Class A chimney from there on up, just like any other installation.

A smoke detector and a CO detector are mandatory, whether you have a wood stove in your skoolie or not.

Finally, have a functioning emergency exit in every room. Don't ever set yourself up with a wood stove between you and the only exit!

[BlueBirdman]

Originally Posted by Kcklr74

Thanks for that information!
I gather from it that if I do it right, it is possible to have the wood stove in the original location?

You're welcome.

Yes, you could have the stove in the original location and still have a comfortable bedroom. A blower in the dividing wall might be enough, but a duct/blower that pushed bedroom air forward to the stove would result in the most even heat distribution.

[dond]

"A smoke detector and a CO detector are mandatory, whether you have a wood stove in your skoolie or not."


Amen.

I had a close one with CO, don't go there.

[bansil]

Originally Posted by dond

"A smoke detector and a CO detector are mandatory, whether you have a wood stove in your skoolie or not."


Amen.

I had a close one with CO, don't go there.

We have 2 smoke detectors (also just 2 rooms) they are mounted on the plastic escape hatches, the highest spot for smoke to collect

And CO detectors at sitting level in front of bus and sleeping level in bedroom area

$100 for 4 life saving detectors ( 2 of each )is an awesome investment

[BlueBirdman]

Thanks for chiming in on the safety aspect, dond & bansil.

Continuing in the safety vein, I'd like to address a comment that was made in the other thread about the possibility a stove could come loose in an accident. I strongly recommend that everyone install a stove designed to be anchored. You have two choices - a marine stove or a stove that is US HUD (Housing & Urban Development) approved for mobile homes.

The thinking is that a mobile home is quite susceptible to high winds and tornadoes, so they want the stove to be anchored well enough to stay attached if the house blows over.

I like having factory provisions to bolt the stove firmly to the floor. I would expect most of those to be strong enough to survive the g loading of an accident, although I'd look at the mounting provisions of any stove I was considering to see just how stout they were. You can always weld something out of heavier steel if you aren't satisfied.

HUD approved stoves must also have a provision for an outside intake for combustion air, which I would strongly consider anyway. FWIW, in the legs vs. pedestal debate, most of the pedestals I've seen were both very stout and built to conceal the air intake plumbing.

[nat_ster]

Kcklr74

I know why you want the wood stove up front, it's to keep the wood hauling through the bus to a minimum. Hauling wood is a dirty chore.

I too wanted the stove near the door. I however moved my door to the center of the bus. Wood stove is right in front of it.
Since I originally drew up my plans, they have changed. Living in my shed this winter has taught me that no stove I can buy meets my needs. I need a stove I can load from the outside of the bus threw a door on the side. This keeps the ash, smoke, bugs, bark and dust out of the living space.
I will still have a glass front door on the inside of the bus for a occasional poke of the fire in the night.

Ash pan will also be under the bus in the storage bay. It will be large enough to hold 200 pounds plus of ashes and have wheels to make emptying simple.

Nat

[gbstewart]

Originally Posted by nat_ster

Kcklr74

I know why you want the wood stove up front, it's to keep the wood hauling through the bus to a minimum. Hauling wood is a dirty chore.

I too wanted the stove near the door. I however moved my door to the center of the bus. Wood stove is right in front of it.
Since I originally drew up my plans, they have changed. Living in my shed this winter has taught me that no stove I can buy meets my needs. I need a stove I can load from the outside of the bus threw a door on the side. This keeps the ash, smoke, bugs, bark and dust out of the living space.
I will still have a glass front door on the inside of the bus for a occasional poke of the fire in the night.

Ash pan will also be under the bus in the storage bay. It will be large enough to hold 200 pounds plus of ashes and have wheels to make emptying simple.

Nat

Load the wood stove from outside the bus, you know that's really good thinking.
gbstewart

[Malkieri]

While you are at inventing a new style of stove, why not add a hopper type set up that you can activate from inside. Not a fully loaded type set-up or anything but maybe a couple chunks of coal or logs (depending on your preference) that you could use in the case of unexpected cold snap or such. You could set it up on a conveyor belt and load the wood sideways into the stove. (parallel with the bus) Then you could set up 5-6 logs/chunks and load it with a button press.


I would think the door opening timing might be a bit tricky, but that sure would be slick! If you could set it up with telescoping arms, it could fold pretty small for moving.

[taskswap]

I haul my wood in those blue IKEA bags. At the store they're $5 apiece, but I found a 10-pack on eBay for like $12. They're WAY more durable than canvas carriers, and have full sides so the mess stays in the bag. They're also waterproof (although the seams go after a couple of seasons) so it keeps melting snow off your floor. When loaded well they are also stackable. Huge fan.

Loading from the outside sounds great from a mess perspective, but I for one love being able to load it in my shorts on a cold morning or when it's snowing/sleeting out. We've dealt with the mess for so long that we're used to it, so...

[superdave]

the only problem with that is having to go outside every time to load the wood. the stove would be small so the fire box would be small so every few hours you would be going outside to stoke it up. to big a stove and it wont burn hot enough.

[nat_ster]

Originally Posted by Malkieri

While you are at inventing a new style of stove, why not add a hopper type set up that you can activate from inside. Not a fully loaded type set-up or anything but maybe a couple chunks of coal or logs (depending on your preference) that you could use in the case of unexpected cold snap or such. You could set it up on a conveyor belt and load the wood sideways into the stove. (parallel with the bus) Then you could set up 5-6 logs/chunks and load it with a button press.


I would think the door opening timing might be a bit tricky, but that sure would be slick! If you could set it up with telescoping arms, it could fold pretty small for moving.

Simple is better, and I dont have the space. I need the versatility to burn wood and coal of all sizes. Hand loading is the only way. Also the stove can't use electricity.

A automatic stoker boiler that uses electricity will be a much later ad on. Once I introduce electricity into the mix, there is no reason to have the stove in the living space of the bus.

Originally Posted by superdave

the only problem with that is having to go outside every time to load the wood. the stove would be small so the fire box would be small so every few hours you would be going outside to stoke it up. to big a stove and it wont burn hot enough.

Your understanding of wood stove sizes is inaccurate. Stove size has nothing to do with how much heat is produced. What your burning, the size of the fuel being burned, amount of intake air, how dry the fuel is, ect all play factors.

I load every 12 to 24 hours. My stove takes logs 24 inches long, up to 16 inches in diameter. Chunks of coal up to 75 pounds. Not a issue for me.

Originally Posted by taskswap

Loading from the outside sounds great from a mess perspective, but I for one love being able to load it in my shorts on a cold morning or when it's snowing/sleeting out. We've dealt with the mess for so long that we're used to it, so...

Coal is simply to dirty to load from the inside, period.

However, My bus will be air tight, so by turning on my fresh air intake blower on the front of the bus, it will pressurize the inside. When I open the stoves interior glass door no ash or smoke will escape into the living space. This will make poking the fire in the morning to flair it up nice and convenient.

Nat

[superdave]

if you dont burn a stove hot enough it will build up creosote in weeks so it can't be two big, too small and your constantly feeding it. thats what i know from the past 40 years of burning wood.b t w my stove takes a 31" log.

[nat_ster]

Originally Posted by superdave

if you dont burn a stove hot enough it will build up creosote in weeks so it can't be two big, too small and your constantly feeding it. thats what i know from the past 40 years of burning wood.b t w my stove takes a 31" log.

You just have to be creative, and burn dry wood.

In spring weather like now, my stoves fire grate stays half blocked by ash. This permits me to burn a hot, small fire in a large stove. Log size still stays large for a long burn time.

Burning coal with wood eliminates the creosote all together. My fires are far too hot.

I have never had a issue with creosote, ever. Even before burning coal.

That creosote is energy that your stove should have burned. The fact that your stove even makes creosote, shows your stove is doing a really poor job of burning the wood gasses. Your stove is highly inefficient.

Be more creative with your stove. By what you have said, you have not taken in the feedback your stove is giving you. Pay attention, and evolve the way you use your stove.

My shed is a really small space. I spend alot of time sitting right in front of my stove. I don't watch TV or occupy my mind with any other mindless junk. Therefore I spend alot of time thinking, and evolving the way I use and do things.
Out of pure necessity, I have leaned how to use my stove to suit my needs. Long burn time and cleaning on a weekly basis was a must. I have achieved both.

Winter is basically over now for us. I used 14 broken pallets, and 2 tons of coal all winter.
Cost, $100 for the coal, and $25 for gas in the truck to haul it to my shed.

Nat

[EastCoastCB]

nat definitely knows a bit about stoves.

I actually, despite growing up in florida, had a wood stove as the only source of heat in the winters until my teens.
Ours was from the late 1800's.
I *may* look around for a small one to use in the bus. It is good heat.
But the selection isn't very good here so I may have to make one if I want one bad enough.

[taskswap]

We burn 12 cords of wood a year. Creosote is overrated, and there are a million misunderstandings that came out of poor communications from various sources with best intentions but bad execution. An average homeowner burning a few armloads of wood a year in a fireplace would need a decade or two to see the kinds of creosote buildup to be a problem.

Creosote is condensed, un-burned combustion compounds and is primarily caused by a combination of incomplete combustion and cool flue temperatures. It can happen with any species of wood. There are lots of ways to deal with it. Hotter flue temps (insulating the flue, using an appropriately-sized flue, etc), damping down a fire less, using stoves with secondary air supplies and catalysts, burning dry, well-seasoned wood, etc.

Example miscommunication/misunderstanding: It is not bad to burn soft wood like pine. We burn at least 2 cords of it every spring and fall during our "shoulder" season. It produces no more or less creosote than anything else - because all of our other conditions are the same. The reason they advise people to not use it is because a lot of people are too inexperienced (or frankly, other, worse words about them) to understand that softwoods tend to have a high amount of resin, which makes them burn very easily (this is why they burn hotter and faster). That makes it MUCH easier to get un-seasoned softwood to burn in the first place, and the high water content makes for a colder fire and colder flue temps - perfect for forming creosote. It is NOT the resin that causes the creosote! It is the colder flue temps and inefficient / incomplete combustion from burning wood that should have seasoned longer. People think if it lights, it's seasoned. Totally untrue.

When I was young my parents/grandparents used to run a super-hot fire for a half hour every morning. You could hear the "crackling" in the chimney. They used to call it "burning out the flue". What it was, was a controlled chimney fire burning off the flakes of creosote that had built up over a night of burning a very damped-down fire. Gasp, a chimney fire. Every day. Whatever shall we do?

Knowledge and experience are priceless commodities.

A steel school bus with a stainless flue pipe is also one of the lowest-risk environments you can have, and super easy to clean if you're at all concerned. But sure, if you ignore it and pretend it isn't going to be a problem, burn wet wood and damp the fire way down, and never clean your chimney - you're going to have a problem.

Nat's point about pressurization is a good one - we have a similar situation and never have any smoke in the house. A good flue providing a good draft on a good (sealed) stove is all you need to avoid that. If smoke is pouring into your living space, something's wrong - not unfortunate, actually WRONG, with your setup.

The bugs and wood junk, I don't know - I guess I'm so used to it I don't notice. We vacuum around the stove every few days the same way we clean the rest of the house. I guess it is a little messy at times but it's not like we're walking on a carpet of wood dust and splinters. It's just some stuff that accumulates around where we set the bags of wood down, the same as around where we put our boots when we come in from outside.

If anybody wants more information about wood burning beyond just what Nat, I, and a few others here say, go hang out on arboristsite.com. There are forums there that are incredibly active with people who cut, process, and burn wood and have been doing so for decades. There's a huge amount of great information there.

[nat_ster]

Well written TankSwap.

Nat

[Roadrunner]

The front of my bus will be fairly open so no problem there. The back will be somewhat closed off. I plan to run a 4 or 5 inch duct from the a register at floor level at the rear with a duct fan inside of it. It does not have to move a lot of cfm. It will terminate near the stove. When you move the coolest air from the floor level it will automatically move warm air to the rear. I have a similar setup in my house and easily heat the whole house with one wood burner. You can run the fan on a timer relay or a thermostatic switch. You could also just run it manually. It should work very well for you. Good luck.