don't go up in smoke! Gasification boilers vs outdoor boilers

When it comes to cheap, easy heat in rural areas, there seemed to be a continuing trend towards outdoor boilers. These "garbage disposal" type wood burners are touted as being able to burn "anything" from freshly cut wood to scap lumber. Unfortunately, these "wood doctor" type boilers are anything but cheap and easy. They are notorious smokers that never seem to offer an efficient burn; efficiency rarely above 50%. Combine that with household garbage that is sometimes disposed of in these units and you have a particularly toxic and polluting heat source.

Then comes the gasification boiler or furnace. These newer boilers use the latest in combustion technology; beyond the "secondary burn" technology offered in woodstoves which has been a huge benefit in home heating.

Where the difference lies between "secondary burn" woodstoves and "gasification boilers" is the temperature at which the fuel is burned. In standard wood burning appliances, it is well known that higher temperatures = cleaner burn. Hence the catalytic converter inserted in some woodstoves. The problem with woodstoves and most outdoor boilers is that they cannot effectively raise the temperature of the combustion chamber without damaging the firebox itself; not above 800°F in a woodstove and 500°F in an outdoor woodboiler.

Gasification boilers operate with a slight difference. First they combust the fuel source (wood) in a low temperature primary burn chamber. This releases all the fuel from the wood in the form of smoke and other gases. Then fresh "super heated" air is injected into this "smoke" as it enters the secondary burn chamber which is lined with refractory brick. This allows the burn temperature to rise above 1800°F offering a clean and efficient flame. All fuel that has been released from the wood is being burned without the use of a catalytic converter. These boilers/furnaces can reach efficiencies above 95% vs 70% for top quality wood stoves and 45-50% for the average outdoor wood boiler. This can equate to a fuel wood savings of hundreds of dollars or many, many cords of wood. If you burn 5 cords of wood in an outdoor wood boiler, you would use 3 1/2 cords with an efficient wood stove or just over 2 cords with a super efficient gasification boiler. Now you see why "cheap and easy" isn't so "cheap and easy"?

choosing a wood stove

So you might be considering a wood stove to heat your house. Assuming you have an abundant source of wood, it is a reliable and satisfying source of heat for your home since it does not rely on electricity to operate as does many wood pellet stove or liquid fossil fuel furnaces. (oil or gas)Also, it is one of the cleanest ways to heat your house using a consumable fuel source.

Contrary to popular belief, burning wood does not add new greenhouse gases to the atmosphere as the CO2 that is released from the combustion process is the same quantity of CO2 that would otherwise be released by wood decomposition if the tree where allowed to rot on the forest floor.

There are many factors to consider when choosing a stove: colour, style, pedestal or legs, size etc. The most important factor is to properly size your wood appliance to make sure it delivers the most efficient heat, cleanest burning and not to either overheat or underheat your home.

The most common error that people make when choosing a stove is to buy one that is too big for the area that it is going to heat. Having too big a stove is actually a bigger problem than too small a stove for the following reasons. With a stove too big, you will need to make a smaller fire to prevent overheating the house. By doing this, efficiency is sacrificed since the firebox temperature is not raised high enough to ensure complete combustion creating a potentially dangerous buildup in the chimney and offering sporadic comfort. A stove too small will mean more frequent refueling, potential overheating of stove or chimney if overfired and insufficient heat for the house. The up-side to undersizing is that combustion efficiency is increased and there is a reduced amount of deposits in the chimney. The ideal size of appliance offers adequate heating, low maintenance and minimal chance of overheating/underheating.

To get more detailed info on heating with wood, download this free publication from CMHC. It is a wealth of information to help you choose your wood burning appliance.







http://www03.cmhc-schl.gc.ca/b2c/catalog/z_getpdf.jsp?pdfkey=2367912238736807498957944372812017562117778745946569768/66067.pdf

Down the drain!

One source of heat that we often forget about is the waste heat from the hot water that we use in our house. This "extra" heat can be recovered very easily and put back to use to reduce our energy requirement for heating. One system uses a simple coil-over drain pipe to recover wasted heat.


As the water goes down the drain, it coats the inside of the stack and transfers the heat to the incoming cold water on it's way to be heated. This system works great for end uses that use water as it is draining such as a shower. It does not however work if you are taking a bath as the waste heat only occurs at the end of the fill cycle, not during.


The best way to recover heat from a bath, or if you don't have a recovery heat stack, is to leave the water in the tub until the temperature has equalized with room temp. Of course, you only want to do this during the heating season as otherwise you would be taxing your A/C unit (if you have one). A second benefit of this is the additional humidity this provides during the "dry" season.