[Janet Flair]

Janet Flair  asked the Naked Scientists:

Hello,
I recently got into a discussion with someone about the various articles that discuss the effects on the environment heating your home with a wood burning stove.

There are many articles online and in print that argue both sides of which method of heating your home is the environmentally friendly way. This spring we had a few large trees come down during a storm, we split the logs ourselves and are now burning them in our EPA certified wood burning stove.

The stove is in the centre of our house and seems to warm it very well, burning little wood at a time. We always burn everything down to nothing and there seems to be almost no smoke coming out of the top. Is this an environmentally safer way to heat my house or am I doing more harm? If it is not, which is the best way to heat a home?

Please help!

Janet
Virginia, USA

What do you think?

[blakestyger]

You can't keep warm without combustion and wood is, in theory, sustainable if more trees get planted. It would be better if the trees were allowed to rot so the invertebrates could benefit, and ulimately the birds, but most gardens don't have that amount of room so you have to do what's practical. I'm a bit surprised that you're able to burn this year's wood as it normally takes a year to season.
I get 4 m³ of logs from a landscape gardener each winter and they last us for open fires in one room till the spring - you can't beat it.

[Bored chemist]

You have to do something to heat your home and I think a wood fire is as good as any. It's renewable and, while the trees are growing, they provide an environment that will benefit other animals and birds.

[paul.fr]

If you happened to live in a valley then it would not be too healthy to you, your friends and family.

[dentstudent]

You can't keep warm without combustion and wood is, in theory, sustainable if more trees get planted. It would be better if the trees were allowed to rot so the invertebrates could benefit, and ulimately the birds, but most gardens don't have that amount of room so you have to do what's practical. I'm a bit surprised that you're able to burn this year's wood as it normally takes a year to season.
I get 4 m³ of logs from a landscape gardener each winter and they last us for open fires in one room till the spring - you can't beat it.

Blakestyger - ash is a very good wood for burning in the same year as felling. Here is a good way to remember....

(http://www.surreycc.gov.uk/sccwebsite/sccwspages.nsf/LookupWebPagesByTITLE_RTF/Firewood?opendocument)

Beechwood fires are bright and clear
If the logs are kept a year,
Chestnut's only good they say,
If for logs 'tis laid away.
Make a fire of Elder tree,
Death within your house will be;
But ash new or ash old,
Is fit for a queen with crown of gold.

Birch and fir logs burn too fast
Blaze up bright and do not last,
it is by the Irish said
Hawthorn bakes the sweetest bread.
Elm wood burns like churchyard mould,
E'en the very flames are cold
But Ash green or Ash brown
Is fit for a queen with golden crown.

Poplar gives a bitter smoke,
Fills your eyes and makes you choke,
Apple wood will scent your room
Pear wood smells like flowers in bloom
Oaken logs, if dry and old
keep away the winter's cold
But Ash wet or Ash dry
a king shall warm his slippers by.

[Karen W.]

very cool wood trivia.. YAYYYYYY! Thanks Stuart!

[JanetCarol]

I really appreciate all of the feedback. I love our wood burning stove! In fact our boxer sleeps on the brick in front of it pretty much non stop.

[Andrew K Fletcher]

Our Log Burner saves us around £700.00 a year. The logs we burn cost £10.00 a load and many times we get them for free. So even if they put the gas prices up by 100%---- 100% of nothing is still nothing

My family plant many trees for the future using "A pocket Full of Acorns" project and we have encouraged many thousands more to plant trees. We don't cut any trees down except for rhododendrun which are highly invasive. In fact if I see saplings I pull them out while walking the dogs. Something we should all be doing in the UK.

The logs we burn are from trees that have fallen or become dangerous and required a bit of TLC. Trees are a renewable resource. The smoke from the wood once the fire is hot is clear and much better than the old coal fires. But most of al it keeps the greedy energy companies out of your pockets.

We also cook on ours by wrapping food in kitchen foil and placing it in the ash pan. Cooked fish, vegetables, jacket potato, chestnuts, corn on the cob (add butter before cooking tastes lovely) Crumpets on a fork, marshmallow, toast. And our particular log burner has a twin boiler on the back so could heat up the hot water for free and run the rqadiators, although the home is warm without this. But certainly going to hook it up to the central heating and install a 4 wat CH pump.

If people wake up to this we could certainly hurt the greedy gas companies.

[dentstudent]

Andrew - I agree. The use of wood for heating and cooking is I think a mind-set thing, but I think that all the while that there is an "easy" option, people will take it.

There are many villages around here that don't have gas, and so use wood, mainly beech, spruce and fir, but with some cherry, birch and oak mixed in. There is a big market for fire wood, and forest owners can receive as much if not more for seasined fire wood as they would for timber. This means that many of the forests are reasonably well managed and have sustainable structures. It is because of the historical small-owners that systems such as the "plenterwald" (single-tree selection forest) and "dauerwald" (continuous cover forests) were created in the first place, which can be used adaptively in today's forests to create "close-to-nature" forest systems.

But then here in Germany, there is a much broader tradition of forest use and integration of the forests with society. It may take some time to rekindle that in the UK.

[Karsten]

Hi there:

I live in Quebec, Canada and teach in Vermont, USA and many people here use a wood stove. Wood is still the least expensive way to heat your house.

There are (at least) two points to consider when it comes to environmental impact.

A wood stove is pretty much carbon neutral. That is a good thing. The CO2 that is released into the environment is not more (or less) than the CO2 that was consumed by the tree when it grew to become a tree and then firewood. Fossil fuels are not carbon neutral (for all practical purposes). They have stored the carbon several hundred million years ago and the release today adds CO2 to our atmosphere when we do not want it. So, if you are worried about greenhouse gases, you are better of with heating with wood than with any fossil fuel.

The other issue to consider is the pollution with particles. Wood smoke contains a lot more dangerous particles than the smoke of fossil fuels. According to this document http://www.burningissues.org/pdfs/WoodSmBroharris.pdf, wood stoves are between 500 to 1000 times more polluting than oil or gas furnaces in regard to PARTICLES. If everyone in Boston or New York city heated with a wood stove, you would not see the city and people would die as a result of respiratory diseases. EPA approved wood stoves burn wood better but only by a factor of 4. And you still have to know what you are doing. A smoldering fire that lasts through the night creates a whole lot more particle pollution than a brightly burning fire that burns out fast. In some places in the USA heating with wood is not permitted. At other times the heating with wood is restricted due to air pollution issues.

Your pick:  If you burn something it is either CO2 pollution or particle pollution. Sometimes both.

BTW, of course it is possible to heat your house without combustion or fire. In many places on this planet you can use simple passive solar principles to heat your house and even make got water. Superinsulation can go as far as heating your (small) house with body heat and a light bulb. Heating with electricity is inefficient, but if the electricity is made with water power you don't have to feel too bad about that. Geothermal residential heating systems are available. Those houses don't even have a chimney. You run a liquid several hundred feet into the ground, it gets warmed (or cooled) by the earth, and a heat pump does the rest. Nothing burned to heat the house - 20 degrees warm/cold in winter and summer here in Quebec.

Hope this helps,
Karsten

[Andrew K Fletcher]

Hi Karsten, Happy New Year and welcome to Naked Scientists.

Another point to consider about having an open or closed solid fuel heater is the draw of air from the living space to the atmosphere. This has a beneficial effect on air circulation in the home providing adequate ventilation is provided to enable the exchange of air.

In bedrooms on the same level as the stove, vents and windows should be closed, this allows the warm air to move into the cold rooms and the cold air is drawn out. Again it is important to have ventilation so make sure you have an adequate open vent in the same room or a room connected without a door to the fireplace. Failure to do this will prevent gasses rising up the chimney and make for a very smoky living environment and a poorly performing stove, which as Karsten says is a greater polluting stove.

Here in the UK, trees often fall due to humans, disease, age, ivy, pollution, floods or storms. These are often mulched and composted. The decaying process of huge amounts of timber is also polluting to the environment during the composting cycle. The timescale is obviously greater, but is there any difference at the end of the day which process is used to return the particles to the atmosphere?

[Karsten]

Thank you for the welcome.

I read somewhere that a decomposing tree MAY create more pollution (greenhouse gases) than a tree that is burned. Don't remember where I read this. It had to do with the fact that anaerobic decomposition may create methane rather than CO2 and methane is a much more powerful greenhouse gas than CO2. Plant matter often decays partially buried or submerged and that creates more methane.

An energy efficient building has a rather tight building envelope. It should not let hot air escape much at all. Warm air escaping is the biggest contributor of heat loss of any structure. This said, if your building is too air tight, you may create an unhealthy indoor climate. You also may not be able to remove moisture that is created in the house well and it may be forced into the insulation. This reduces your house insulation dramatically and may result in mold problems. This said, the American Society of Heating and Refrigeration and Air Conditioning Engineers (ASHRAE)recommends whole house air exchange of not less than 0.35 per hour. Modern home often are more air-tight than this and you need to provide mechanical air exchange and ventilation. You cannot own a house that has too much insulation, but you can own a house that has too little ventilation.

To relate all this back to the topic here, some wood-stoves use outside air directly for combustion. Stoves approved for mobile home are even required to be installed that way since modern mobile homes are build so efficiently. That way you do not need to worry about getting a smoky interior even if your home is appropriately air-tight (which is should be to save energy).

Karsten

[lyner]

There are systems which allow reasonable ventilation yet reduce heat loss by means of heat exchangers which warm the inlet air with the exhaust air. It's an expensive capital outlay but can save a lot in the long run.

[elmejor]

i dont think it is good for the environment! at least i would like to believe that!

[lyner]

i dont think it is good for the environment! at least i would like to believe that!

Which?

[Karsten]

Believe???

[WilliamLaurence]

I bought one of these heat exchangers from [link removed] and it is Stainless Steel. The rest of the pipes in my house are Copper and some plastic. I get a tremendous amount of heat from this thing and I am worried that it will melt the copper or plastic tubing.

The heat coming out of the chimney heater is about 190f does anyone know if this is to hot for the copper or Plastic pipes in my House?

[CliffordK]

I have thought that we could do better with heat exchangers.
Most stoves use heated exhaust gasses for "draft" up the chimneys.  Cool the exhaust too much, and the stove doesn't draft properly.  It also has a potential to deposit more creosote in the chimney.

My design would be to cool the exhaust to room temperature, and use forced air input for drafting.  It would require a sealed firebox.  I'm not sure about the creosote problem.

As far as efficiency.  To a large part it depends on the access to wood.  I can get much of my wood needs from natural deadfall, which might otherwise be burnt in an open burn pile (which often is done much greener than wood used in a fireplace).

[peppercorn]

My design would be to cool the exhaust to room temperature, and use forced air input for drafting.  It would require a sealed firebox.  I'm not sure about the creosote problem.

Some gas fires with horizontal flues have air drawn out by an electric-fan, so it is workable.  And having a fan running would save having to ensure heat was left in the flue gases for draw. Wood creosotes are not going to do an electric fan any good but a vacuum is preferable to pushing cold air in through the fire, especially the need to load more wood.

[CliffordK]

My design would be to cool the exhaust to room temperature, and use forced air input for drafting.  It would require a sealed firebox.  I'm not sure about the creosote problem.

Some gas fires with horizontal flues have air drawn out by an electric-fan, so it is workable.  And having a fan running would save having to ensure heat was left in the flue gases for draw. Wood creosotes are not going to do an electric fan any good but a vacuum is preferable to pushing cold air in through the fire, especially the need to load more wood.

Perhaps if you could clean the creosote with a water bath or something, then a cool exhaust fan would be workable.

If one used forced air, then one could simply have a direct bypass to hit before opening the door.  I think the biggest problem is that a pressurized system would tend to blow bad air around the door seals.