Heating Water with Fire (2019)
homewoodstoves.co.nz
homewoodstoves.co.nz
It was a big cast iron contraption, with what I remember as white powder-coated sides and trim, and she knew how to get the temperature just right for whatever she was cooking.
I remember walking downstairs on cold winter mornings to the smell of ham, eggs, and biscuits, all prepared on that thing.
One more thing I remember. It was positioned about three feet from the wall. There was enough room to walk behind it (if you ducked under the pipe), and our dog used love napping there.
According to this article from 1993, it was a toss up in terms of cost savings then:
https://nasdonline.org/1359/d001154/do-you-waste-money-by-he...
Since that time, heat pumps have become much more efficient at a wide set of operating temps, and the cost of wood has gone up, so it's unlikely that a wood stove is cheaper to operate, unless you have your own forest, and are willing to fell trees and chop and dry firewood yourself.
I've got one of these https://pyroclassic.co.nz/ - it's not a new design but is quite clean (it's usually impossible to tell if a fire is going by looking at the chimney) and efficient as far as these things go.
The lifetime cost of the equipment itself must be lower for an efficient wood stove+flue than an efficient heat pump, in both dollars and environmental impact. The initial install cost here in NZ is a little bit higher for the fire, but annual maintenance (flue sweeping) is something an average homeowner can do in an hour or so, where heat pumps need regular cleaning from the homeowner, and are supposed to be checked on by a technician periodically. The fire can reasonably be expected to last half a century with a few minor repairs. When it eventually does need a full replacement, that's just some steel and ceramic - no electronics, refrigerants, or plastic involved.
Electricity here is expensive - last bill was NZ$0.42/kWh - and wood isn't so much. My last batch of primo firewood was IIRC NZ$100 per tossed m^3, and yes that takes some time to stack and such (firwood warms you twice!), however there's also a fair bit of free wood to be had.
To use round numbers, say the heat pump is 250% efficient making heat, and the fireplace is 50% (after writing most of this, I see that fireplace is claimed to be 74% efficient). That tossed m^3 of firewood is about 0.2 (stacked) cords and contains about 1170kWh energy from some quick searching, so $100 in firewood gives 586kWh heat in to the house. The same heat from a heat pump would've cost $98.45 - the difference is a decent pint or two per year in heating the house...
But, the biggest argument is that you don't actually use a heat pump in the same way as a fire. It takes a while for the fire to start cranking out heat, so I only build a fire if it's worth having one going in an hour or so. If I had a heat pump, I'm sure we'd have it turned on in the morning as well as evening, so it would be used to put out substantially more heat than the fire does.
Heat pump cooking isn't really a thing either...
I miss the smell of the oak from the old boiler, but not the smoke or absurd amount of wood we were going through.
I understand it takes a fair bit of experimentation to learn how to cook on one. :)
I was talked out of it by the fireplace guys and the plumbing guys. Now I regret it every time I light the fire.
The main problem is that wetbacks fall into a gray area, they are mainly plumbing, but plumbers are more used to dealing with standard components and materials. Architects are usually not familiar with them so don't push for them.
In a video they show their home setup and how the stove is used as a stove, oven, heater and water heater. I wish I could have one of those.
I'm curious about this. Around here the carbon from the wood (less emissions from a relatively small amount of petrol to cut and transport it) would've been taken out of the atmosphere in the last 20-ish years, where the natural gas carbon is in the millions of years (and additionally a much longer supply chain). I understand that smoke particles are not great in the short term, but assume we're talking about modern equipment.
First and foremost - at a time, when every bit of CO2 not emitted counts, we should be happy about CO2 being fixated in trees - once it's released, it doesn't matter whether the it is coming from jet engines or wood - the effect on climate change is the same. Furthermore, burning wood is quite inefficient in terms of mass/energy gain - even worse than coal.
But besides that, there are a lot of systematic effects which make wood a non-neutral source of energy and making use of it as energy source comes with a lot of issues. Even if wood would be completely neutral, it would still be negative due to the energy required to harvest, process and transport it.
Trees don't only sequestrate carbon in wood, but also in the forest soil through their roots. Decaying wood is processed by microorganisms and mycelium in the soil, so it's not only about the tree itself capturing CO2, but also about it being part of a more complex sequestration system which is disturbed by removing the tree.
Cutting down single trees from an otherwise intact forest as part of a "sustainable forestry" strategy is actually often quite problematic, as the sudden exposure to sun & weather leads to decreased survival rates of fresh growth, but also soil erosion and thereby CO2 release - not even taking the damage of harvesting machinery etc. into account.
Those "wounded" forests decrease the Earth's Albedo which also adds to climate change.
Last but not least are forests not simply something that can be "renewed" by replanting trees, but are extremly complex ecosystems which might take millenia to build up.
Right now, we're cutting down massive amounts of old growth around the world which can never be properly restored - we're far from managing wood like a crop on designated "farms".
With technologies available like Passivhaus construction, heatpumps, solar and/or geothermal energy, there's zero reason to add to our systemic issues by using wood as an energy source.
When it comes to particle and toxic emissions, there isn't a single non-industrial wood burner that would only come close to the emissions of a gas or oil furnace (not saying they're good, as they're using fossil fuels). The best even modern filters will get you is still worse by factor of ~400-500 compared to oil.
You're a landowner and need to decide how to use your land (ed: which has already been cleared of native bush). Practically, the usual choices are something like:
* Dairy farming
* Subdivide and build residential sprawl
* Crop farming
* Forestry (introduced tree species)Or, you're a homeowner and need to decide how to heat your existing, likely built to a low/nonexistent efficiency standard, house. Your choices are:
* Heat pump, usually poorly located/installed
* Electrical resistance heaters where needed
* Burn wood
* Burn coal
Woodstoves are not widely used in major habitated areas (cities and suburbs) in advanced countries. They're a primary heating source principally in rural areas, where population is sparse. Or, of course, in developing countries where other heating options aren't available.
When woodfuel was a principle fuel source, forests were indeed being cut down faster than they could regrow just to provide fuel. And some of the oldest enviromental regulations and restrictions in the world address the sustenance and conservation of woodlands. The aphorism that "forests preceed mankind, deserts follow" has a great deal of truth to it. It was exhaustion of fuelwood throughout Great Britain, Ireland, and mainland Europe that lead to the adoption of coal, and the burning of coal which largely lead to the resurgence of European forests.
In developing countries, fuel avaiability and woodstove (or other solid fuel, often animal droppings) particulate emissions are major energy security and health concerns.
At small scale, and for occasional use, in areas with abundant tree growth, fuelwood is viable. Given present human population densities, at a large scale, it is not.
Unfortunately, that's not the case for large parts of Western Europe, where wood-based heating is considered eco-friendly, due to it being classified as "renewable". For example. in Germany you'll get 40% of a wood-pellet burner subsidized. Many villages and also towns are plagued by heavy air pollution. Emissions from those by now have surpassed those by cars, according to the German federal environmental agency. [1] Scientific findings and political action don't match up at all here - some other European countries slowly start to address this issue, but then again UK is pushing for the Drax power plant which runs exclusively on wood pellets whose wood sources are highly problematic [2].
[1] https://www.umweltbundesamt.de/daten/luft/emissionsminderung...
[2] https://www.biofuelwatch.org.uk/2021/draxs-pinewells-case-st...
I'm contesting that it's widely used.
Wood / pellet stoves in dense urban environments are a small fraction of total cooking and heating load.
And I'm also arguing precisely your point: that woodstoves widely used are a major pollution and deforestation issue.
There may be some variation based on pricing any given day, but my understanding is that this is pretty common when harvesting mixed forest (as opposed to a monoculture forest).
We got three cords delivered last year that was mostly black birch, red oak, and white ash, and we burned two, supplemented by propane that kept the overnight low around 50F/10C inside. Our hot water, incidentally, is tankless propane.
OK, but making complete use of the wood is hardly the same as harvesting timber specifically for firewood.
Also, relatively speaking, little of the species you're burning are used for lumber. And you can't throw a rock without hitting a dead ash tree these days.
The reality is: huge amounts of protected forests (e.g. in Romania or Estonia) are cut down and sold as firewood in central Europe.
Also, if a dead tree is laying on the ground and your options are 1) use it to heat your home, or 2) leave it the to mushrooms and bugs and burn fossil fuel instead, then if the environment is your concern, I don't see how you could pick the latter. Keep in mind that one of the best things about heating with wood is that it takes a tremendous amount of effort on the part of the end user. Cutting, splitting, stacking, starting a fire, feeding the stove, adjusting the stove, taking out the ashes. Some of us enjoy it, but it's definitely a lot of hard work, and I'd argue all the time you put into it makes you far more in touch with how much energy you consume than someone who simply twists a dial on the wall and kicks back to Netflix. You might even choose a much smaller house and wear a sweater.
I've hiked in a forest in Romania. Despite the fact that it was a great place to be eaten by a bear, it was spectacular and a resource to be treasured.
Some of the wood I could buy in the U.S. is birch harvested in the Baltics. I've seen videos of harvesting operations that are definitely harvesting live birch and splitting it with equipment that's all designed with that in mind. But I've got no proof for you!
https://www.doc.govt.nz/nature/pests-and-threats/weeds/commo...
The notable invasive species where I live is ailanthus. I've burned some out of curiosity. It's better than pine, but not worth the trouble when you're tripping over red oak.
I should point out that there are plenty pine species that aren't considered invasive pests like wilding pines are; for example one of our bigger exports is radiata pine.
OP is right that it's dirty as hell, by modern standards.
Specifically particulat matter / PM2.5 emissions, the same factor that causes most concern in wildfire smoke.
My home for instance was built in the 1950s, and in the attic has a copper "header tank" which has an overflow/vent to outside and a float valve to maintain a set water level in it. That would've supplied one or two heat exchangers in the wood/coal fires, and cold water at the same pressure.
Now, the header tank is out of the circuit, the original fires were removed decades ago in a remodel (their water heating functionality replaced with a "low pressure" electric hot water cylinder which still vents through that same pipe), and we're now connected with city water. The current situation is like many homes of similar vintage and has a couple issues: the cold water is substantially higher pressure than the hot, and we now have an Ajax valve which occasionally needs to be checked on in case it's leaking through and pumping electrically-heated water out on to the roof.
How big is that pipe that goes up to the roof? I assume it's covered with something to avoid random debris or animals from getting in?
From memory, the pipe is just a piece of 1 inch copper. There's nothing on the top, it just points straight up to the sky.
Do you not use your stove for cooking as well? I guess most people with a wood-burning stove us it as an oven, a hob, a toaster, things like that, which they want to use during summer as well.
But even then I don't leave my oven on 24/7. This article runs under the assumption that your heat source is constantly running. In fact he advocates for large tanks that take a long time to warm up in most cases because of the assumption that your stove is always burning.
Yeah that's the way many of these combined heater / oven things work - the oven is literally on all the time. Starting it up can take a full day.
Maybe the small tank system would make sense for a bachelor who is ok with taking a shower only at night after cooking dinner. Maybe supplanted with a solar thermal setup to keep the water at an elevated temperature and only topped off with the stove?
I have to admit I thought to myself a few times while reading the article: "Is this better than a solar array and electric water heater?" I guess it has fewer failure points, although a solar panel failure doesn't flood your basement. If you are running a wood stove from trees you chop down on your own land this could be very low cost over the long term I guess. Solar is still fairly expensive, especially if you add battery storage, but it has been falling sharply in the past few years and the price for these systems is basically fixed. At the end of the day it's a decent chunk of custom plumbing and a specially designed appliance. Traditionally that combination would be fairly expensive and I wouldn't be surprised if the price has been increasing slowly as the plumbers who know how to do this retire and the wetback stoves become even more specialty equipment.
https://www.google.com/search?q=wood+burning+aga&safe=active...