permaculture

[Mark <mpludwig@facstaff.wisc.edu>]

Hi Misha, nice to see your still spunky!
At 01:34 PM 11/21/02 -0800, you wrote:
> Howdy, all--
>
> Based on my experience with wood fuel for heating in Pennsylvania, 
> Wisconsin, California, and here in Oly, I'd say Mark's comments on wood 
> stoves contain dangerous oversimplifications and some outright misinformation.
>
> I'd say, Frank, that you should talk to as many people as you can ***who 
> actually use wood as the main or only source of heat for their homes, 
> workshops, etc.*** Abstractions or guesses are not what you need.

I have heated with wood throughout my childhood and in several rentals with 
varying success.  I agree with a lot of what you wrote, I'll comment a bit 
as I go along...


> > The biggest source of trouble with wood stoves in houses are old chimneys 
> > catching fire or poor installation decisions causing trouble (ie- 
> > flammable floors and walls to close.
>
> Arguable at best. Dangerous and misleading at worst. The biggest source of 
> trouble with woodstoves in houses is indoor air quality and outdoor air 
> pollution, with carbon monoxide poisoning sickness and death a huge issue. 
> That happens regardless of the age of the stove or the chimney.

A matter of perspective perhaps?  I'm much more concerned with burning the 
house down than sucking a little smoke while working the bugs out of a new 
system, and I know how poor many old chimneys are, especially if they have 
been unused for years.  Smoky fires also tend to spur people to action, 
while ignorance of chimney conditions can continue indefinitely.

> Chimney fires can cause property damage. But the Journal of the American 
> Medical Association estimated in the late 80s that 1,600 people a year 
> died from CO poisoning.  Countless more people go to hospitals for the 
> nausea, headaches, and other problems caused by CO buildup in indoor air. 
> Not all of this was caused by woodstoves. My point is that there's a big 
> difference between property damage and mortal injury.

Having been a victim of CO poisoning ( in someone elses house) from a badly 
vented gas furnace I can agree it's a problem (tip o the day - check the 
chimney for squirrel and raccoon nests before you fire it you for the 
season).  However, unlike a gas furnaces exhaust which is more less 
orderless, a badly vented wood stove is pretty apparent.  IMO you have to 
be pretty unobservant to miss that.

> Chimney fires can happen in new chimneys and stacks as well as old ones. 
> It's a matter of how the firings are managed, and how much creosote builds up.

True, I was more concerned with broken tile in the old flue or loose 
mortar.  Another factor is that many farms people move to may have suffered 
some degree of neglect due to declining health/wealth of the previous 
owner, hence the need to inspect the flue, preferably by a professional 
before you fire it up.

> In most places code takes care of installation decisions that would lead 
> to fire of the kind Mark alludes to.
>
> Following code for wood stove installation WILL hugely reduce the 
> likelihood of fires of the sort mentioned above (combustible surfaces too 
> close to the heat). But many more fires and poisonings are caused by 
> things that can't be controlled by code--the layers of common sense and 
> attention needed to use a wood stove so it combusts cleanly and vents gases.

Again, true.  How many folks will look at the code though?

> --Creosote buildup, which results from cool firing temperatures, burning 
> unseasoned wood or trash
> --Poor drafting (which can be caused by a user too inexperienced or lazy 
> to adjust the damping as needed)
> --Packing the firebox and letting it smolder, rather than making serial 
> small, hot fires

all good advise, especially adjusting the damper.  Stoves are all basically 
regulated by manipulating air flow and fuel size.

> >   Catylist or no?  A catylist wood stove should burn cleaner and more 
> > efficiently, and I think they are supposed to keep the chimney cleaner.
>
> A catalytic wood stove will only burn cleaner and more efficiently if used 
> properly, and with good, seasoned fuel.
>
> All wood stoves require the user to have more sense than the log in the 
> stack, and  some attention to the firing. Low firing temperatures and poor 
> fuel will creosote up any stove--catalytic or not--or stack, and will 
> release particulate (smoke) which otherwise would be combusted at proper 
> firing temps. All the catalytic converter does is heat up, to reburn the 
> smoke. If the converter isn't hot enough, it can't do that, and in fact 
> gets fouled, then ineffective. Just like in your car.

true again, though frankly you can cheat a little, get the fire temperature 
up and then retard it a bit once the fuel is hot during the day if you 
can't be home to tend it.  Just make sure you get it hot enough regularly 
(2-3X daily) so the flue gets cleaned out and make sure you get the chimney 
cleaned annually or better.  A lot of folks do not like the catylist stoves 
precisely because the catylist can be temperamental.

> In any event all wood stoves should have their stacks cleaned regularly. 
> Some say every 90 firings.
>
> My goal in all firings is to go behind the house, look up, and see nothing 
> coming out of the stack but heat wiggles. No smoke AT ALL. I'm working now 
> on developing a kindling system that will achieve that state more rapidly, 
> reducing the smoky start-up cycle; it seems to be much easier with 
> well-seasoned Doug-fir and alder than it ever was with Wisconsin or 
> California oak, ironwood, or maple. I'll report on that as things develop.

Certainly a laudable goal, though many folks will burn what they have 
rather than search out the perfect wood.  Your idea of looking at the smoke 
is a good one, we all need feedback.


> > You may also want to make some provision to vent combustion air near the 
> > stove in order not to create negative pressure in the whole house with 
> > the stove's demand for air.
>
> This is misleading. As well as inaccurate--drafting isn't a simple matter 
> of "venting combustion air near the stove" (what does that mean?).

What I mean is that the stove will draw air from the house and vent it up 
the chimney.  There is some advantage IMO to supplying this air from the 
outdoors close to the stove, rather than drawing it from the house as a 
whole.

> It isn't combustion that creates negative pressure in a house. Strictly 
> speaking, a stove can't draft, and therefore can't burn, with negative 
> pressure in the house. When negative pressure happens inside, relative to 
> outside, you get a downdraft. By definition. And your fire goes out. Older 
> houses have lots or cracks, and sometimes don't need a draft window. Newer 
> houses tend to be tighter.

Agreed.  I think we're really on the same page here.

> And regardless of how strongly a stove is drafting, you can get a 
> downdraft under various conditions. That's caused by external changes in 
> air pressure relative to the indoor air pressure OR changes in indoor air 
> pressure due to opening and closing doors and windows, turning on bathroom 
> vent fans, or starting up an externally-vented cooking hood. That can 
> happen whether a draft window is open or not.

Still much less likely if you have a source of outdoor air close to the stove.

> Downdrafts are more of a problem with taller stacks/chimneys. For example, 
> we had this EXACT SAME model and year stove in the townhouse we rented in 
> Berkeley for 10 months. I had a helluva time getting that thing to draft.
>
> Here, in a one-storey house, I can get a draft going in basically the same 
> stove by setting a wood match to a couple of alder twigs. There are also 
> geographical reasons for this.
>
> I find that our stove burns much more cleanly when the cracked window (to 
> support drafting) is AWAY from the stove, NOT near it. This also sets up a 
> movement of air that helps cycle the heat thru the room.

Interesting.  Any theory why this might be happening?  How far away are we 
talking here?


> It's not real windy here, but when we have serious swings in wind 
> direction (NW to SE or vice versa), I shift from opening a north-facing 
> window (library, front of house) to an east-facing one (over the kitchen 
> sink). If the wind swings to the opposite side of the drafting window, it 
> can create a pocket of negative pressure there.

This is an excellent point.  Perhaps if one wanted to try providing 
combustion air from one location you could box it in or shelter it from the 
wind to prevent problems.


> > If your chimney is junk you may be able to drop a tipple walled stainless 
> > steal flue down the existing pipe.  You may also find your home owners 
> > insurance demands this or at least gives you a better deal with one.
>
> This is dangerously oversimplified for those of us living in rural areas.
>
> Do not mess around with these retrofits without knowing code and talking 
> to your insurance people. You can literally render your house 
> "uninsurable" with a bad decision on this.

.

> Retrofitting furnaces is tricky and can be mortally dangerous--I would 
> never drop a stainless steel flue down a "junk chimney." It could easily 
> heat up and ignite layers/pockets of creosote already in there. The 
> chimney could lose structural integrity and damage the metal stack. Lots 
> of things. Bad infrastructure needs repair, not jerry-rigging, where 
> something as serious as potential fires and toxic gases are concerned.


marks reply...
> I believe this is the industry standard for saftey these days.  These are 
> three nested stainless steel tubes, essentially a double heat shield.  I 
> very seriouly doubt you could start such a fire, especially if you had the 
> sense to clean the chimny before dropping in the new flue.  BTW - Misha's 
> right about consulting local code and using pros to do this kind of work, 
> it is nothing to mess around with just for the insurance factor if nothing 
> else.  Another option for old chimnys is to use a long balloon to form the 
> flue and pouring special cement mix down the old flue to stabilize the 
> chimny.  This also reduces flue volume which can help with some of the 
> cavernous old chimnys you see in old farm houses
>
> > The out door furnaces are a matter of continuing controversy. Personally 
> > I like them, keeps all the fumes, bugs etc out if the house, lets you 
> > heat multiple building with one furnace, can't burn down the house.
>
> I take exception to the above. There are not fumes OR bugs in the house in 
> a well managed cordwood-heating system. Unless you mean the occasional 
> spider or cricket, without whom no home is complete.
>
> It takes very little attention to examine wood when bringing it indoors, 
> knocking each piece on the ground or against the pile. We take kindling 
> off of split logs while restacking it from the main woodpile to near the 
> patio door. This gives us ample opportunity to examine each piece for 
> infestation, and then again as we bring it indoors. We have a plastic 
> Critter Bin into which the occasional piece of infested-looking wood goes. 
> The creatures (termites, carpenter ants, wood borers) get knocked out and 
> squashed (with a prayer). The wood gets burned that night once the stove 
> is fired to 500 degrees plus.

Whatever.  Some people like wood in the house some don't.  When I was a kid 
we would throw 3 cords at a time into the house from our outdoor stacks and 
be inundated with critters for weeks.  Since we were all biologists, 
trained and feral, it wasn't so bad.  Would have driven some of the folks I 
know batty.

> In any event, when the soon-to-be-burned wood is seasoned the second time 
> in the stove corner, any critters quickly make themselves seen. One 
> pillbug, one cricket, and three spiders got in the house in the last two 
> weeks. Big deal. I picked them up and carried them back out, except one 
> little black spider, who I put in my office because I needed one there 
> after I kicked the hobo spider out.
>
> As for fumes--where on earth does it say that stove-burning of cordwood 
> puts fumes in the house? That's a symptom of a poorly managed or flawed system.

Well the door does have to be open some time to fill it up, I don't care 
how good you are you will get a puff there.  These outdoor units also 
frequently have very large fire boxes, capable of heating several 
buildings.  My in laws have one and really like it.

> Moving inattention outside is no answer. You can burn down your house with 
> an outdoor furnace as an indoor one--in part because you're suddenly 
> dealing with heat exchange issues and complexities in air and gas 
> movement. You can have fumes flow from your combustion source into your 
> house with an external woodstove.

Hogwash.  How would you burn down you house with one of these?  blow it 
up?   Where would the fumes come from?  All the units I have seen use hot 
water to do the heat exchange, though I suppose there could be a forced air 
model out there.  The rest of your post is very informative, but this is 
total nonsense.

> > There definitely is some loss of heat in the run of pipe from the furnace 
> > to the buildings, might be better if there was sufficient insulation of 
> > the pipes.
>
> My father designed and constructed ventilation for large ships for 42 
> years. He would say that heat movement and loss are NOT a simple function 
> of insulation, but of air movement, air and heat exchange, barometric 
> pressure, fuel quality, infrastructure features,  whether the captain 
> farted, and many other factors.

like insulation.

> Systems involving heat and cold, air movement, fire, and gases aren't 
> simple. "Might" is a dangerous answer.
>
>
> > remember to factor in your insurance savings on the outdoor furnace.
>
> If indeed there are any. It's dangerous to assume there are without 
> actually knowing.

I encourage people to call their agents.  Most of them don't like indoor 
stoves.

> This varies a lot from state to state, company to company, and even agent 
> to agent. The risk factors for various sorts of solid wood heating systems 
> in various sorts of structures and settings vary a lot. Our insurance 
> office required an inspection of our woodstove and stack, and we live on 
> rural land, outside of many of the bureaucratic complexities of city 
> living. However, there are also no hydrants here on Cooper Point; water 
> must be trucked in from the firehouse two miles south. A lot of a 
> cedar-shingled, frame house can burn in 15 minutes. Creosote stack fires 
> can get up to 2000 degrees F., quickly igniting surrounding structures and 
> melting metal parts.
True, I like metal roofs for this reason.
One last tip we both missed, look over any wood stove you buy for good fit 
of parts and rusted out fire boxes on used units.  Though durable they 
don't last forever.


> peace
> misha
>
>
>
> _______________________________________________
> permaculture mailing list
> permaculture@lists.ibiblio.org
> http://lists.ibiblio.org/mailman/listinfo/permaculture

Mark P. Ludwig
Poultry Research Lab
University of Wisconsin -Madison
608-262-1730 WK
608-846-7125 HM