Tag Archives: wood burning

Is a pellet stove right for me?

First firing of the pellet stove at the UAF Sustainable Village, which serves as a backup heater in the northwest house.

Pellet stoves are a relatively new wood heating appliance, similar to wood stoves in concept but they have automated operation and burn processed biomass.

Pellets are manufactured from compacted sawdust, wood chips, agricultural crop waste, waste paper and other materials. They can also be made from biomass fuels such as nutshells, corn kernels, sunflowers and soybeans. Pellets are about 1 inch long and look like rabbit food. The pressure and heat created during production binds them together without the need for glue. Pellets are manufactured in Alaska, including at Superior Pellet Fuels in North Pole, and are available at local hardware stores and by delivery from manufacturers.

How it works

Stoves are designed to heat a space directly. The stove consists of a combustion chamber, ashtray and flue to vent exhaust gases. In a pellet stove, the flue can be direct-vented through a wall, meaning that no chimney is required. Pellets are stored in a hopper near the stove. The hoppers come in various sizes, but generally can hold enough pellets for the stove to run for more than a day.

Pellet stoves use electricity to run three motorized systems:

A screw auger feeds pellets into the fire at a controlled rate
An exhaust fan vents exhaust gases and draws in combustion air
A circulating fan forces air through the heat exchanger and into the room

The motorized systems are controlled by a control system and allow pellet stoves to operate automatically.

Pellet stoves do not have a distribution system. The fire inside the combustion chamber causes the stove to warm up and radiate heat throughout a room. Pellet boilers are available that use a hydronic distribution system.

Maintenance

As with other wood-burning devices, pellet stoves require frequent maintenance, yet less than a wood stove. The stove should be inspected regularly. Also, the hopper must be filled and the ashtray should be emptied on a weekly basis (though this depends on the size of the hopper and ash tray and the frequency of use).

Additionally, the stove should have a yearly check-up. Heating professionals can check that the doors, gaskets, electric connections and seals on the stove are in good condition. They can also check the chimney for creosote, rust, and corrosion.

Efficiency Range

Pellet stove efficiency ratings are published by manufacturers. The efficiency ratings combine electrical efficiency, combustion efficiency (a measure of the heat produced from burning fuel), and heat transfer efficiency. Efficiencies can range from 78–80%. More efficient stoves lose less heat up the chimney and deliver more heat into the home.

For more information on home heating devices check out these resources:

–Consumer Guide to Home Heating:

http://cchrc.org/docs/reports/Consumer_Guide_Home_Heating.pdf

–Your Northern Home: http://cchrc.org/yourhouse

How long does it take to cure firewood in the Interior?

Firewood can dry in a single summer if split and stored properly.

While we won’t mention the dreaded “W” word, it’s never too early to start thinking about the heating season, when many Interior Alaska residents burn wood for heat.

While wood burning is a cheaper and more renewable alternative to heating oil, it also contributes to the air quality problem in the Fairbanks North Star Borough. Burning wet wood produces excess smoke and PM 2.5-sized particles, which disperse into the air and can be harmful to health. These emissions can be lessened by burning dry firewood. Fully cured wood — moisture content of 20 percent or less — is not only cleaner but also produces more heat.

How long does that take in this climate? It depends on the species of wood, when you harvest it, how you cut it and how you store it. A study at the Cold Climate Housing Research Center shows that wood can dry rapidly during a single summer — no matter when it’s harvested — but takes quite a bit longer over the shoulder seasons or winter. No matter what wood or method you use, firewood harvested in the fall won’t be fully cured by winter.

In our study, split wood harvested in the spring took anywhere from six weeks to three months to dry during the summer, depending on the storage method. Split birch and split spruce, for example, dried in one and a half months when stored in a simulated wood shed or left uncovered. In general, the fastest way to dry split wood was by storing it in a wood shed or leaving it uncovered, although uncovered wood is at the mercy of the weather and could be wet again by fall. When stored under a tarp, the wood took three months to cure.

Unsplit wood, on the other hand, didn’t cure during the summer in any storage scenario. Though it neared 20 percent moisture content by the end of the summer, it required another summer to reach a full cure.

Firewood harvested in the fall didn’t cure by springtime no matter how it was cut or stored. While it dried out somewhat in a wood shed (to between 30 and 40 percent moisture content), some samples got wetter under a tarp during the winter.

Several other factors should be considered when seasoning your wood. Spruce and birch tend to dry more quickly than aspen. Your drying times also will vary based on exposure to sun and air circulation (the more, the better).

The good news is that it’s possible to harvest firewood in the spring and cure it during a single summer — so you can stay cozy and burn cleanly during the winter. Just make sure to split it early and store it so it can dry.

The “Ask a Builder” series is dedicated to answering some of the many questions Fairbanks residents have about building, energy and the many other parts of home life.

Read more: Fairbanks Daily News-Miner – Ask a Builder How long does it take for wood to season

Why are masonry heaters so popular?

How is wood burning different in a masonry heater than in a regular wood stove?

A masonry heater is designed to burn a large charge (amount) of wood in a short amount of time at extremely high temperatures, upwards of 1800 degrees F. The heat from the combustion process is stored in the mass of the stove. In order to effectively store heat, masonry heaters are quite heavy and weigh thousands of pounds. Because the heater is designed to be fired as hot as possible, it will consume a day’s worth of wood in a matter of a few hours, at which point the chimney and air intake are closed off. Once a burn is completed, the heater will radiate its stored heat for a period of 24 hours or longer at very comfortable and even temperatures.

Although masonry heaters have been common in Europe for hundreds of years, they have only begun to enter the spotlight in the US within the last 20 years. They are gaining in popularity for several reasons. The high combustion temperatures produce extremely clean burns with virtually no creosote buildup in the flue passages, which translates into some of the lowest particulate emissions attainable through wood burning. Since the heater will extract the most heat energy it can from a piece of wood, it uses less wood overall, important where firewood is a limited resource.

It should be noted that a masonry heater is a long-term investment and may command a price easily several times that of a top-of-the-line wood stove. The brick core of a masonry heater is carefully engineered for performance and it takes a skilled mason to construct the heater to insure that it drafts properly and can withstand the expansion and contraction of thousands of firing cycles. Since the heater is so large, the best time to install one is during the construction of the house, where it can more readily be incorporated into the home’s design and heating requirements. The good side to this is that a masonry heater can easily last a lifetime, or even several life times.

One of the best resources for more detailed information regarding masonry heaters is The Masonry Heater Association of North America www.mha-net.org. For local viewing, the Cold Climate Housing Research Center has a 12,000 pound heater in center of its lobby which heats roughly 3200 square feet of office space. The heater is fired Monday through Friday during the winter season, typically in the mornings, and burn times last around four hours.