Should I use my wood fireplace?

Question

I live in a relatively modern (built 1983) home, which has a fireplace in the living room. How should I decide if I should use the fireplace for heat, or strictly use use the natural-gas central heating system?

I have an open fireplace, situated roughly in the center of the living room, which in turn is in the center of the house. The fireplace will not completely replace the central heating system, but if it will help reduce my environmental footprint, I'd love to use it to reduce my NG usage.

And although I think it's slightly tangential, in response to some other comments/answers, I will only be using free firewood.

Answer 1

I tend to think renewables (like wood) are a more sustainable heat source than natural gas. There are tradeoffs of course. Most fireplaces are pretty inefficient and can result in a lot of particulates. A wood stove (sometimes mistaken for regular fireplaces) or a pellet stove ensure much more complete burning of the fuel (wood), but require an extra up front investment and represent some embodied energy. If you're not burning enough wood energy to make up for the embodied energy of the wood insert, that's probably not worth the investment.

Another thing to consider is the positioning of the fireplace. Is the fireplace in a central location? If it's off to one corner of the house, you may have more heat radiate outside the home than you actually benefit from inside the home.

Finally, do you have a source of good dry wood? If you're buying wood that gets shipped from somewhere other than your own property, the fuel required for transportation may offset the relative carbon savings of using a biofuel.

Answer 2

Open fireplaces provide minimal heat to a house, as the warm air heads out the chimney, while cool air is sucked in to the house to replace it. This is a great feature when cooking over wood in the summer, but it's not helpful for staying warm in the winter.

You can buy a woodstove insert that will improve the efficiency, keeping more of the heat in your house.

If you are interested in a major project, look at high thermal mass stoves, which can be extremely efficient when burning wood.

As rethinktag mentions, moisture content of wood is extremely important. All the latent moisture in wood must be evaporated before the wood can get hot enough to burn. Wetter wood means more heat devoted to drying the wood out, which means burning more wood. Wetter wood also means cooler fires, which means incomplete combustion, leading to increased air pollution.

Answer 3

A fire in a fireplace is pretty to look at but is probably the most inefficient way to heat a home. Not because wood is a poor fuel, which it really isn't, but rather that it is an incredibly poor design for a heating source. A huge amount of the heat goes straight up the chimney.

If you really want to use wood as a fuel source the most efficient way to burn it would probably be a rocket mass heater.

If your main concern is decreasing energy consumption you can accomplish this more easily by focusing on heating the people rather than the house. A blanket or a well placed heat lamp can decrease your heating bill far more than lighting up the fireplace.

Answer 4

There's two things to consider when looking at the efficiency of a wood stove:

• Clean, complete burning - wood stove rely on natural convection to supply air to the fire. This usually means in practice that the stove is most efficient when it's burning "full throttle", meaning most of the wood in the fireplace is actually burning.

• Form of the heat - in an open fire (with flames) most of the thermal energy is conained in the exhaust gases. In most cases, this will go up the chimney - though I don't know your setup.

This makes it hard to efficiently heat a home with fire - though pellet stoves (where a small fire is maintained automatically) or stoves with huge thermal mass (that evens out the heat output over time) are good ideas.

In your case, I would suggest conducting an experiment - assuming you can see and access your gas counter, you can monitor how much gas you use with and without using the stove to augment your heating, at the same time measureing (weighing) your wood consumption. One week with, one week without wood stove (given roughly the same weather and daily/weekly pattern of living) could give you some data to base your decision on.

Answer 5

Be careful with wood fireplaces — most emit A LOT of very bad particulate matter!

Burning wood in a common type of stove may result in more particulate matter than a diesel truck and may carry more carcinogens than a diesel or petrol exhaust. In the United Kingdom, where many people have such stoves or even open hearths, wood burning generates twice as much PM2.5 as all traffic combined. In many urban areas, burning wood is prohibited (I don't know if those bylaws make exceptions for modern, cleaner stoves). Globally, biomass is estimated to be responsible for 250,000 casualties per year, as the overwhelming majority of biomass burning takes place with open fire or primitive stoves.

From an environmental point of view, burning solid fuel at home may be much worse than you think, depending on the type of fireplace you have. Wood may be (at least potentially) be carbon neutral, that does not mean the exhaust is anywhere near healthy to breathe. Check the characteristics of your fireplace before you assume that wood is carbon neutral and therefore environmentally friendly.

See this article in The Guardian:

Wood smoke is thick with the tiny particulates, known as PM2.5, that are linked to heart attacks, strokes, cancer, dementia and various other ailments. What’s more, the claims about a climate benefit from wood use are questionable.

Cars and trucks get more attention but nationally, domestic wood burning is the largest single source of PM2.5. According to one analysis of government data, it produces more than twice as much as all road traffic. While concerns about diesel vehicles focus largely on the nitrogen dioxide they produce, the evidence tying particulates to death and disease is even more powerful.

According to Leigh Crilley, an atmospheric chemist at the University of Birmingham, wood smoke also carries more carcinogens than diesel or petrol exhaust.

The increasing popularity of wood fires, scientists warn, threatens to erase any progress big cities might achieve in reducing pollution from traffic. “It’s overtaking the gains we’re making,” Crilley said.

One study from 2014 found that wood smoke was adding more particle pollution to London’s air than the first two phases of the city’s low-emission zone were expected to remove. In London and Birmingham, King’s College researchers reported wood accounted for up to 31% of locally produced particulates. And across Europe, wood burning is worsening pollution in capitals such as Paris, Berlin and Lisbon.

Cities are moving toward it:

The mayor of London, Sadiq Khan, asked the Department for Environment, Food and Rural Affairs (Defra) in September for the power to ban solid fuel use (wood, coal and the like) in high-pollution areas of the city, starting in 2025, which would require amending the Clean Air Act.

If you live equatorward of 60°, there is in theory no need to actively heat your home. The most sustainable thing you can do, if you can afford it, is to upgrade your home to passive house standards and you can dispense with any sources of space heating altogether (you still need hot water, of course, but most wood fireplaces are impractical for this purpose).

There may exist specialised high pressure/temperature or perhaps heavily filtered wood fireplaces that exhaust much less or no particulate matter. If you insist on burning wood, investigate the particulate matter exhaust of your technological choice. Being carbon neutral is not enough; air quality must be part of your sustainability budget, in particular if you live in a populated area.

NB: This answer is focussing purely on what is best from a sustainability point of view. Of course, many people around the world cannot afford any other source of cooking or heating than wood fires, just like they cannot afford access to clean water, access to sewage, or the only vehicle they can afford is a very dirty scooter. Sustainable solutions often cost more out of pocket, which puts policy makers in a very difficult dilemma. Humanity must all work together to improve the economic situation of rural and urban people around the world such that we can all sustainably stay warm and cook. However, if you are purely asking from a sustainability point of view, there are far better alternatives than burning wood — in particular if your fireplace is typical.