Tag Archives: Heating

Tips for Storing Wood Pellets

Pellet stoves are similar to wood stoves, except they burn manufactured pellets instead of cordwood. Pellet stoves typically use electricity because they are partially automated: An auger moves pellets from a hopper to a combustion chamber, an exhaust fan vents combustion gases and draws in fresh air, and a circulating fan forces air through a heat exchanger and into a room. The stoves also can be controlled by a thermostat.

Pellets are about a half-inch long and are made from compacted sawdust, wood chips and waste paper (they resemble rabbit feed). They can be made from biomass fuels other than wood, including nutshells, corn kernels, agricultural crop waste, sunflowers and soybeans. They are bound together by pressure and heat (no glue is used). Pellets are sold in 40-pound bags at local hardware stores, or you can buy them by the ton from a manufacturer.

Many homeowners store pellets near the appliance because the hopper needs to be filled occasionally by either the homeowner or through a separate automated system. For small appliances only used occasionally, you may only need a few bags on hand, but bigger or more frequently used appliances will need a greater pellet supply. Below are a few guidelines to follow for storing pellets:

1. Ideally, pellets should be stored near the pellet-burning appliance for convenience. The pellet storage location must be accessible for re-stocking as well. If you have pellets delivered, call the manufacturer to make sure a delivery truck can access the site.

2. Pellets must be kept dry so they don’t crumble, ideally stored in an area with a roof and walls. If stored on the ground, they can absorb moisture from wet soil.

3. Since they will be burned in an appliance, they should be kept as clean as possible — protected from dust and other contaminants. On that note, delivery trucks that blow pellets into a storage area can cause lots of dust, so the room should be sealed off from the interior of a home.

4. In Alaska, pellet delivery trucks typically use a direct auger system to transfer pellets into a storage system. If you order pellets from a manufacturer, ask how they will be transferred to the storage area and protect any fixtures, lights or pipes that could be damaged. Make sure the storage area can support the weight of the pellets.

5. Finally, the storage area should have ventilation and a carbon monoxide (CO) detector near the door, as pellets can release CO when stored. Another option to alleviate CO concerns is to store pellets in a silo (inaccessible to people entering it) outside of the occupied building, with an auger feed system into the pellet appliance hopper and a CO detector near the


This last point is important because CO is a clear, odorless, and tasteless gas that prevents red blood cells from carrying oxygen. It is extremely dangerous because people cannot detect it. Typically, CO is associated with burning fuel in a combustion appliance, such as wood, pellet, oil or natural gas furnaces and boilers. CO can enter a home if a combustion appliance backdrafts, releasing combustion gases into a home instead of up the chimney.

Stored pellets can release CO, according to recent studies, though the amount depends on several factors, such as the age, content and exposed area of the pellets. This is especially a concern for enclosed storage areas that contain large quantities of pellets and are accessible to humans, such as for district heating systems or on cargo ships.

Not all pellets release measurable amounts of CO. Preliminary testing at CCHRC found no detectable CO emissions when the pellets were stored in a 30°F storeroom. Although when we sampled a plastic bag filled with pellets, sitting inside an 85°F room, the CO concentration in the bag was 60 parts per million (70ppm would trigger CO alarm if sustained for 1 hour). While the room may not have reached the same level as the bag (as the gas would have more space to diffuse), this shows the pellets have the potential to produce CO.

Be sure to take the proper precautions for a pellet storage area by ensuring the area is vented, installing a CO detector near the storage area, and being aware of the symptoms of CO poisoning. All homes with any kind of combustion appliance should have a CO detector in the living area to ensure combustion gases are not entering the home.

How can I use thermal storage in my home?

 A 5,000 gallon tank acts as thermal storage in a home heated by a solar thermal system. Photo Courtesy Reina LLC.

A 5,000 gallon tank acts as thermal storage in a home heated by a solar thermal system. Photo Courtesy Reina LLC.

CCHRC recently completed a study on how you can use thermal storage as part of your home heating system.

Thermal storage has recently gained interest in Alaska as it has the potential to increase the efficiency of heating appliances, enhance the use of renewable energy in cold climates, and reduce emissions of certain appliances like wood boilers. It is most suited for renewable energy systems such as solar thermal, geothermal and biomass, but can be adapted to a wide variety of heat sources. The report looks at different design considerations and describes several examples in homes around Alaska.

Thermal storage is a common concept. Many households use water storage tanks to provide domestic hot water, which can range from just a couple gallons to more than 100 gallons. Thermal storage also can be used in space heating systems to store heat for a certain period of time. For example, storing the heat from solar collectors in a buffer tank to use at night; storing heat from a wood boiler in a water tank to allow for a hotter, more efficient burn; or storing heat in the ground to harvest later with a ground source heat pump. In each case, thermal storage can be thought of as a “heat battery” because it holds energy to be used later. In this way, it can enable a heat source with intermittent delivery (like the sun or wind) to still meet demand.

Every thermal storage system needs three basic components: a heat source, a storage medium to store the heat (such as a tank of water, rocks or soil), and a discharge method (heat exchanger) to distribute the heat. Technically, any heat source can be used to charge a thermal storage material, however you should select the fuel and storage material based on availability, cost and compatibility with your home’s needs.

Also, many factors will drive the design of a thermal storage system for your home — such as your heating appliance, your distribution system, your heating demand, your lifestyle and many others. The design of the system also will depend on whether the system is being installed in a new home or being retrofitted into an existing one, as retrofits must accommodate the existing distribution system and available space in the home.

There are various applications of thermal storage throughout Alaska. A net-zero heating home built in Fairbanks several years ago uses solar thermal collectors and a masonry heater to charge a 5,000-gallon insulated water tank that provides heat to a radiant floor system.

The tank also heats domestic hot water in the house.

A different system, located at CCHRC, uses a wood-fired boiler to charge an insulated 1,500-gallon tank of water in the lab. The goal was to fire the boiler hot and fast, which produces more Btu and fewer emissions, and save the heat to use when it’s needed, rather than damping down the boiler so the fire lasts longer.

The water tank heats 1,900 square feet of lab space in the building. The tank was sized to hold as many Btu as the boiler could produce in one firing per day and to provide enough heat for the entire lab over a full winter day.

If you’re considering a thermal storage system, the first step is to consider what your goal is. Do you want to use renewable energy instead of fossil fuels? Are you looking for short-term (a few hours or overnight) or seasonal storage? Systems that are recharged daily are smaller and less expensive than seasonal systems.

Check out the report for an overview of various types of systems used in cold climates, case studies in Alaska, and tips for designing your own system.

Report: www.cchrc.org/docs/reports/thermal_storage.pdf

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.


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:


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

Glycol not always best for hydronic systems

Adding glycol to your hydronic heating system is one way to boost the frost protection of your heating system, but first consider if it’s a good match for your system.

Every winter, several days of sustained cold temperatures tend to produce their share of frozen pipes. In the long term, the best way to protect water pipes is by addressing the source of the problems rather than the symptoms. This means insulating and air sealing the walls, floor, foundation or other cold spots that are putting those pipes at risk in the first place. If necessary, consider rerouting water lines to ensure they stay in heated space.

When it comes to the hot water (hydronic) heating system, solutions may not present themselves as readily. In many instances the piping may be inaccessible such as in concrete slabs, or the freezing risk may be too great if a mechanical breakdown occurs. In such cases, bolstering a heating system’s frost protection with glycol may present the best option. Although glycol is quite effective at keeping pipes from freezing, its use does have some important considerations as it has properties that differ from those of water.

For residential heating systems, propylene glycol is most often used as it is non toxic and environmentally friendly. Even so, make sure the glycol is compatible with your particular system and that it contains the proper additives. Typically, an experienced plumber will perform an inspection and decide what changes your particular heating system may require to make it compatible with glycol. Water hardness, the presence of chlorine and other impurities, and the metals used in the system (such as aluminum), can alter the system requirements and the additives in the glycol.

In some cases, a system where glycol has been added may experience weepage. Simply put, this means that marginal areas such as weak solder joints, pipe threads and other fittings that didn’t leak before may experience some leakage with glycol in the system. If leaks occur, they will need to be addressed. Fluid treated with glycol will expand to a greater degree and your expansion tank may need to be upsized. Also, since glycol does not transfer heat as well as water, depending on the amount in the system, this may result in a noticeable loss of system efficiency and a corresponding increase in heating cost. Ideally, glycol should be tested every year or two to ensure that its performance hasn’t degraded. Test kits are available at plumbing stores, or a plumber can test the system as part of routine boiler maintenance. In a properly operating system, glycol can last 10 years or more.

Along with the considerations mentioned above, glycol is an investment and introducing it into a system carries significant expense. Consequently, not every home may see the benefit and many have done fine without it for years, however there are times where it is the best solution for freeze protecting a heating system. Because every case is unique, what matters most is an experienced plumber is there to judge, inspect, and if needed, add glycol to the system to ensure the best possible performance with the fewest complications.

How do I know if my boiler (or furnace) is the correct size for my house?

If you are thinking about purchasing a new boiler (or any other heating appliance) in the near future, make sure that you get one that is the optimal size for your house. Correctly sized boilers operate more efficiently and are able to keep your house at a comfortable temperature. A boiler that is too small will not be able to produce enough heat in the winter months, and a boiler that is too large will cycle on and off, wasting fuel, just like a car driving in stop-and-go traffic. Here are 3 ways to know if your current boiler is the correct size:

1) The rule-of-thumb: On the coldest day of the year, your boiler should run pretty much non-stop to keep the set temperature. Think of it as a car driving on the highway, getting a high miles-per-gallon since it doesn’t have to start and stop. If it does run non-stop, but your house does not stay warm, then the boiler is undersized. On the other hand, if you find your boiler cycling on and off during January’s coldest week, then you should consider getting a smaller boiler.

2) The calculations method: To determine what size of a heating appliance you will need, in addition to finding out information about what other energy upgrades you can make to your house, consider signing up for an energy rating. An energy rater will look at your entire house, measuring the air leakage rate with depressurization from doors and windows, checking insulation levels, assessing your heating system and checking for drafts. They will input this information into AKWarm, software maintained by the Alaska Housing Finance Corporation that calculates energy ratings. In a few weeks, you will receive the rating in the mail. It includes ways to improve the rating and other information on your house, such as the heating needs. An energy rating typically costs between $425-$550, but this will be rebated if you participate in the Home Energy Rebate Program (though you will likely face a waitlist for the rating). Visit the Alaska Housing Finance Corporation website for information on the rebate program and signing up for a rating: www.akrebate.com.

3) Do-it-yourself: The rating software AKWarm is available for free online. If you are computer-savvy and have a few hours to gather information on your house, you can use AKWarm to calculate your own unofficial energy rating. The software is available for download here: www.analysisnorth.com/AKWarm/AKWarm2download.html.

What is a combined/integrated heating system?

Many homeowners use the same appliance to heat both their house and their domestic hot water. These multipurpose appliances are called combined or integrated systems.


Hot water for space heating goes into a hydronic distribution system or to coils for forced air distribution, while domestic hot water goes to a storage tank or directly to the faucet. Combined systems work with several types of appliances, including boilers, ground source heat pumps or solar thermal systems.


Combined systems offer several advantages over distinct systems. Since an integrated system provides both domestic hot water and space heating, you have fewer appliances to maintain. During the heating season, it’s more efficient to have a single appliance providing both hot water and heating because you have fewer on-off cycles. It also saves space.


On the downside, combined systems can be less efficient when the heating appliance only fires occasionally—in summertime, for example. In addition, it’s tough to measure the efficiency of combined systems because the rating on the appliance (known as the AFUE) only applies to space heating, not domestic hot water. A heating contractor or someone who owns the same appliance can give you a better idea of the actual efficiency.


There are two types of combined systems—storage tank and tankless. Storage tank systems are most popular. In this setup, the appliance simply sees the hot water tank as an additional zone, but one that is separated from the space heating system to avoid contamination of the drinking water. When the domestic hot water tank calls for heat, the appliance sends heat to that zone. Having a storage tank forces the appliance to fire only a few times a day to provide hot water. This design is more efficient than a tankless coil system because the appliance doesn’t have to fire as often, which is an energy-intensive process. Also, since there is no burner on the storage tank you can add extra insulation to the tank to save energy.


A tankless coil system has an extra heat exchanger that fits into the appliance. Water is heated when it flows through the heat exchanger. Tankless coil systems are most efficient when the appliance is already being used for space heating. During summer months, however, the on-off cycling that occurs every time domestic hot water is needed can waste energy. To avoid this, some homes use a tankless coil system during the winter and a separate domestic hot water system during the summer.


How do tankless hot water systems work and are they really more efficient?

Tankless hot water systems, also known as on-demand heaters, only produce hot water when you call for it—by turning on the sink, shower, or other appliance. They heat water instantly as it runs through a pipe and deliver it to your point of use, so you don’t have to store hot water in a tank and heat it all day. These on-demand heaters can be powered with propane, natural gas, or electricity.

You can save energy with this kind of system because you’re not paying to heat water when it’s not being used and you eliminate stand-by heat losses. Another benefit is that you never run out of hot water, unlike a tank system.

But a tankless system is prone to control and pressure issues. One problem is that on-demand heaters can produce bursts of cold water. For instance, if you finish taking a hot shower and turn off the water, the heater will shut off but the water in the pipes will remain warm (because they’re insulated). Yet the water inside the heater will cool off. So the next bather thinks the water is hot, jumps in, and soon gets a blast of cold water making its way through the pipes.

Another limitation of tankless heaters is that they can only heat a certain amount of water per minute. So if the washing machine is turned on during a shower, the hot water is split between the two uses, reducing water pressure all around. The good news? Both of these problems can be solved by adding a couple accessories to your system.

You can prevent cold bursts of water by adding a small, 2- to 10-gallon electric water heater (like a mini water tank) in between the tankless water heater and the point of use. This creates a buffer between sections of chilly water and your showerhead. The heater and installation will cost about $450.

The pressure issue can be fixed by adding a large pump to the system that can push enough water through the heater to accommodate multiple hot-water users at once. Adding the pump will cost about $650.

These add-ons drive up the price of a tankless system from around $300 (for the low end) to more than $1,000. Meanwhile, a hot water tank costs between $200 and $900. If you can live with idiosyncrasies like variable temperature and pressure, and don’t want the add-ons, then the tankless system will pay off in just a few years (thanks to energy savings). If you desire a system that is free of idiosyncrasies, the payback period will be much longer.

Electronically Commutated Motors: are ECMs worth it?

There seem to be many ways to save energy in home heaters and air handlers. Recently I’ve been hearing about “ECM” motors in these appliances. What are they are and are they worth any extra expense?

There are many ways that manufacturers are increasing the energy efficiency of their products. You’ve probably seen the Energy Star rating on new appliances. Since 1992, the Federal government has been giving tax incentives and rebates to manufacturers and/or consumers for making improvements like reducing the amount of water needed to wash a load of towels or the amount of electricity needed to run your refrigerator.

One of the ways of accomplishing energy use reduction is by using electronically commutated motors (ECM). The construction of these ECMs allows the motor to run at different speeds, depending on the demand from the appliance. This type of motor has been in use in the US since 1985 and uses as much as 67% less power than that used by standard motors (PSC). That’s because sensors in the motor determine the need of the system and provide just the amount of energy needed. ECM motors are also quieter and cooler than standard motors.

A simple system that uses ECMs these days is a home hot water distribution system such as radiant-heat floors. The ECM runs the pump which distributes the hot water to heat your rooms. A sensor in the system measures the temperature of the fluid in your system and tells the pump to run only as fast as it needs to to heat your rooms.  When run most efficiently, your system using an ECM could use less power than a standard light bulb.

HRVs (heat recovery ventilation systems) are also now made with ECMs. Just as with the hot water circulator pump, the HRV’s motor will vary its speed (and therefore energy use) based on the demands from the building. When you push your “booster” button in the kitchen, the motor will run the fan at a faster rate and exchange more air for a set period of time. When the HRV is operating at its normal (lower) level, it will use less power and run less forcefully.

While it is possible to have a professional retrofit your current furnace, HRV or other appliance with an ECM motor, it is generally more cost-efficient in the long run t to purchase a new appliance. Some appliances are not configured to allow the conversion at all – the older it is, the more this is likely.


Weatherization and Indoor Air Quality Issues

BY: Ilya Benesch, Cold Climate Housing Research Center
Energy Focus: Fairbanks Daily News-Miner September 4th, 2008, Section A3

With the dramatic increase in heating fuel prices, we have been seeing a flurry of activity from both homeowners and contractors to improve insulation values and reduce the air loss in homes around Fairbanks. This is a good thing and something that has been long overdue, especially in some of the older houses. With this surge in home improvement activity, there are a few issues centered around indoor air quality to be aware of. It is important to keep in mind that as you attend to your home’s weak spots, you are likely making the house envelope tighter. This means it may be necessary to introduce fresh air in places where previously it may not have been required. Fortunately, there are a variety of solutions available. They can be as simple as installing an air duct to an appliance and improving exhaust fans, on up to complete Heat Recovery Ventilation Systems (HRV) that can supply fresh air to the whole house while minimizing heat losses.

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