10-03-2009, 10:13 AM
Wood burning appliances in general and open fireplaces in particular can be very polluting and often are so, but they do not have to be. Whether or not they are depends to a huge amount on how they are operated. Shockingly, in the 70 when wood burning stoves came on the scene in large numbers, many people actually would cram them full of wood and choke down the air so that there would be a few embers left in the morning. Think of filling your tank every evening then letting the car idle overnight with the choke on full just so you wouldn't have to start it in the morning. Car or woodstove, the results are the same; clouds of greasy black smoke, terrible waste of fuel, and a filthy exhaust system that will eventually impair the operation of your appliance, if not actually catch fire. Nevertheless there were those who were proud that they could do this and would describe with satisfaction how their stove would burn (smolder more like) all night. Modern clean burning wood stoves are so well designed and automated that they make it difficult for the user to screw things up. However any old metal box can be operated relatively efficiently and cleanly if your wood is properly seasoned, if you build several small hot fires, and if you never choke the air down. All the bells and whistles on modern stoves are there to help the stove burn cleanly under part load conditions. Don't ask your stove to operate under part load or less than ideal conditions and it will burn cleanly. For the operator this means a lot more stove tending, being nearby to feed it wood in modest amounts when it can handle it, getting up at night if need be or just tolerating the cold till morning. Frankly a lot of this is a lot bigger deal in cold climates. Here, light a fire in the evening then let it go out overnight.
Fireplaces are a much different animal. I define a fireplace as being open. Fireplace inserts or other airtight appliances are merely wood-stoves with big glass doors. Frankly, fireplaces will never compete with any kind of airtight appliances as far as efficiency is concerned as long as we are talking the standard enclosed family residence where we expect the air to be warm. This is because of the vast amount of air that goes up the chimney, which must be replaced by air that leaks in from outside. Wait a minute, I am thinking of the frigid northeast in winter again. Here in Hawaii, and here in this thread, we are actually looking for a way to ventilate the house. I can't recall where I read this (decades ago) but I distinctly remember reading that the ancient Romans in Italy used a fireplace in a back room where nobody went to cool and ventilate the house in the evening when it began to be cooler outside than inside. As long as you were not in line of sight with the flames the fire did not heat you, and everywhere the air leaked in it was obviously the same temperature as the outside. To this end these Roman fireplaces were made especially deep with small openings so the heat couldn't get out and again nobody went near them unless they wanted to get warm.
In the American Colonies in Benjamin Franklin's time fireplaces were used for heat in the winter. Keep in mind that there was no central heating. I read an article in the Conservationist magazine published by the DEC of New York State about what it was like to live in New York in the 1700s. Houses were build of logs or rough clapboards. Tyvek house-wrap did not exist and houses were extremely drafty. People relied on foot thick down quilts and occasionally woke up with snow on their beds. Yes, there were snowdrifts indoors. It was the fireplace or nothing. Some brave soul would get up and start the fire and everyone would cluster around it. The old wingback chairs were not just a style. When facing the open fire they kept the inevitable draft of cold and recently outdoor air blowing toward the fireplace off of your neck and created a little microclimate within the confines of the chair where a certain level of comfort could be achieved.
Benjamin Franklin did research on enclosed wood stoves because of his concern over American dependence on "sea coals", coal shipped by sea from England of all places. A contemporary of his, Benjamin Thompson, later known as Count Rumford, a loyalist who left in a hurry during the revolution, also spent a lot of time thinking about fireplace efficiency and went on to invent the Rumford Fireplace. Like the roman fireplace, it was a simple open fireplace. Unlike the roman fireplace, it was extremely shallow and designed to capture the smoke with as little air going up the chimney as possible while putting as much flame in line of sight with the living space as possible. It is fascinating to think of the same device, a fireplace, being optimized to do two diametrically opposed tasks, one being to provide as much ventilation with as little heating as possible and the other to provide as much heating with as little ventilation as possible.
No matter what, any open fireplace will produce a substantial draft. If optimized and operated properly they can also provide quite a bit of radiant heat. In fact they are a better source of heat for open areas than any other because radiant heat goes in a straight line and is unaffected by drafts, so if you want to heat an open area, there is no other way. I have seen LPG radiant heaters for sale at Costco for use on patios. Finally, if operated properly, they can also be clean burning, but this takes a properly designed and built Rumford type fireplace and extreme attention to detail. Heat from an open fireplace is like a salmon swimming upstream. The draft caused by the fireplace is like the current. The heat has got to rapidly get past the worst of the draft or it will simply get swept downstream and up the chimney. Radiant heat does this when it shines against the end user or against the opposite wall. Heat absorbed by the fireplace stones is like a feeble salmon. It never makes it past the rapids and soon winds up downstream.
Five paragraphs on how to burn wood. Gawd, I must be some kind of a pyromaniac. Anyhow it seems to me that an open fireplace could, if done right, be a classy way to get both warmth and ventilation, both of which are necessary for humidity control.
Fireplaces are a much different animal. I define a fireplace as being open. Fireplace inserts or other airtight appliances are merely wood-stoves with big glass doors. Frankly, fireplaces will never compete with any kind of airtight appliances as far as efficiency is concerned as long as we are talking the standard enclosed family residence where we expect the air to be warm. This is because of the vast amount of air that goes up the chimney, which must be replaced by air that leaks in from outside. Wait a minute, I am thinking of the frigid northeast in winter again. Here in Hawaii, and here in this thread, we are actually looking for a way to ventilate the house. I can't recall where I read this (decades ago) but I distinctly remember reading that the ancient Romans in Italy used a fireplace in a back room where nobody went to cool and ventilate the house in the evening when it began to be cooler outside than inside. As long as you were not in line of sight with the flames the fire did not heat you, and everywhere the air leaked in it was obviously the same temperature as the outside. To this end these Roman fireplaces were made especially deep with small openings so the heat couldn't get out and again nobody went near them unless they wanted to get warm.
In the American Colonies in Benjamin Franklin's time fireplaces were used for heat in the winter. Keep in mind that there was no central heating. I read an article in the Conservationist magazine published by the DEC of New York State about what it was like to live in New York in the 1700s. Houses were build of logs or rough clapboards. Tyvek house-wrap did not exist and houses were extremely drafty. People relied on foot thick down quilts and occasionally woke up with snow on their beds. Yes, there were snowdrifts indoors. It was the fireplace or nothing. Some brave soul would get up and start the fire and everyone would cluster around it. The old wingback chairs were not just a style. When facing the open fire they kept the inevitable draft of cold and recently outdoor air blowing toward the fireplace off of your neck and created a little microclimate within the confines of the chair where a certain level of comfort could be achieved.
Benjamin Franklin did research on enclosed wood stoves because of his concern over American dependence on "sea coals", coal shipped by sea from England of all places. A contemporary of his, Benjamin Thompson, later known as Count Rumford, a loyalist who left in a hurry during the revolution, also spent a lot of time thinking about fireplace efficiency and went on to invent the Rumford Fireplace. Like the roman fireplace, it was a simple open fireplace. Unlike the roman fireplace, it was extremely shallow and designed to capture the smoke with as little air going up the chimney as possible while putting as much flame in line of sight with the living space as possible. It is fascinating to think of the same device, a fireplace, being optimized to do two diametrically opposed tasks, one being to provide as much ventilation with as little heating as possible and the other to provide as much heating with as little ventilation as possible.
No matter what, any open fireplace will produce a substantial draft. If optimized and operated properly they can also provide quite a bit of radiant heat. In fact they are a better source of heat for open areas than any other because radiant heat goes in a straight line and is unaffected by drafts, so if you want to heat an open area, there is no other way. I have seen LPG radiant heaters for sale at Costco for use on patios. Finally, if operated properly, they can also be clean burning, but this takes a properly designed and built Rumford type fireplace and extreme attention to detail. Heat from an open fireplace is like a salmon swimming upstream. The draft caused by the fireplace is like the current. The heat has got to rapidly get past the worst of the draft or it will simply get swept downstream and up the chimney. Radiant heat does this when it shines against the end user or against the opposite wall. Heat absorbed by the fireplace stones is like a feeble salmon. It never makes it past the rapids and soon winds up downstream.
Five paragraphs on how to burn wood. Gawd, I must be some kind of a pyromaniac. Anyhow it seems to me that an open fireplace could, if done right, be a classy way to get both warmth and ventilation, both of which are necessary for humidity control.