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Old 03-18-2015, 02:35 PM   #1
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Wood Stoves/Heating

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.
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Old 03-18-2015, 03:35 PM   #2
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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.
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Old 03-18-2015, 04:38 PM   #3
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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?
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Old 03-18-2015, 05:02 PM   #4
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Clearances/Heat Shields

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!
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Old 03-18-2015, 05:09 PM   #5
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Quote:
Originally Posted by Kcklr74 View Post
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.
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Old 03-18-2015, 05:48 PM   #6
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"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.
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Old 03-18-2015, 07:45 PM   #7
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Quote:
Originally Posted by dond View Post
"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
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Old 03-18-2015, 09:03 PM   #8
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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.
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Old 03-18-2015, 10:28 PM   #9
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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

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Old 03-18-2015, 10:40 PM   #10
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Quote:
Originally Posted by nat_ster View Post
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.
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