Tag Archives: CCHRC

What are Vacuum Insulated Panels?

Vacuum insulated panels, or VIPs, are a relatively new product making their way into buildings in the United States.

They can be used as stud cavity insulation or as continuous exterior insulation on structures, just like other types of insulation.

As the name describes, VIPs consist of a panel with the air inside of it removed to form a vacuum. It isn’t a perfect vacuum, but the air pressure inside the VIP is considerably less than ambient pressure. The panels are airtight and resistant to water vapor absorption. They make good insulators because the lack of air almost completely eliminates conductive and convective heat transfer through the center of the panels. Typical panels are fairly small, 1 x 2 feet or 2 x 4 feet, and about 1 inch thick.

VIPs have an R-value of approximately R-25 per inch at the center of the panel and about R-20 for the whole panel (exact R-value depends on the manufacturing process and materials). The center of the panel will have a higher R-value than the edges, much like a window, as edges provide a thermal bridge for conductive heat transfer and lower the R-value of the entire panel. Even the whole-panel R-value is considerably higher than other insulations: fiberglass batts are around R-3.8 per inch, EPS is around R-4 per inch, and XPS is around R-5 per inch.

VIPs are installed on the sheathing plane of a building using adhesive. The material surrounding the VIPs in a wall is very important, because it helps protect the VIP from damage during installation. However, because the VIP is not continuous, the lower R-value surrounding insulation will bring the total wall R-value down. This is similar to what happens in a traditional stud-framed wall with fiberglass batts in the cavities — the wooden studs provide a thermal bridge for heat to escape and reduce the total wall R-value. With VIPs, even if the “studs” were made of EPS insulation, the whole wall R-value will still drop more than the fiberglass wall drops with the addition of wooden studs. It is important to consider how to provide structure for VIPs without providing too much thermal bridging.

As with any new building product, there are potential disadvantages of using VIPs that must be considered. First, VIPs must be manufactured in a factory and then shipped to the building site.

They can’t be cut or modified in the field. This means that detailed plans must be completed prior to construction and there is no flexibility in modifying them, unlike a traditional stick-framed wall.

VIPs also cost quite a bit more than other types of insulation. In addition to the more intensive manufacturing process, the panels have to be shipped to the building location.

There are currently only a few manufacturers in the United States, so this could be quite a long distance.

Finally, panels will naturally lose some vacuum over time. When they do, the R-value drops substantially. Manufacturers currently estimate the lifespan of the vacuum at 25 to 50 years. The seals must be treated carefully during the shipping and installation process to protect the vacuum. And putting a nail through a VIP damages the R-value of the panel much more than with other types of insulation. Losing the panel vacuum due to a hole in the panel reduces the panel’s R-value by more than half, often bringing it down to around R-6 per inch.

VIPs in Alaska

VIPs have a number of applications throughout the world, including refrigeration equipment, vending machines, shipping containers and construction. A few companies are manufacturing them in the United States, including Nanopore and Dow Corning. The new engineering building at the University of Alaska Fairbanks will use Dow Corning VIPs in a test wall system, which consist of fumed silica (basically glass powder) wrapped in a layer of plastic and aluminum. In effect, the plan is to replace some EPS foam in the wall system with a small vacuum panel. UAF researchers are planning to measure the installed R-value of the panel to study its appropriateness for buildings in our climate.

Moisture Performance of Cellulose Insulation

Blowing dense-pack cellulose insulation into the test walls.

Blowing dense-pack cellulose insulation into the test walls.

Building envelopes have a hard job in Interior Alaska—keeping us warm, dry and healthy at 40-below. CCHRC tests a variety of building designs and products to see how they can be applied in this environment. We recently studied the moisture performance of cellulose insulation to see how it compared to other common types, like fiberglass and rigid foam, and how it performed in a super-insulated house.

First, let’s look at a conventional wood-framed wall with 2×6 or 2×4 studs and an interior vapor barrier. This system has historically worked in the Interior because the vapor barrier limits the moisture allowed into the walls and moisture that does sneak in remains frozen through most of the winter. During the spring, the walls thaw and dry to the outside.

But when you add exterior foam insulation to a house, a common retrofit technique to save energy, the walls can no longer dry to the outside. Is this good or bad for the wall? Depends on how much you add. If you add enough exterior insulation (for example, six inches of EPS foam for a 2×4 wall) the sheathing and framing will stay warm enough to avoid condensation, improving your overall moisture control. If you don’t add enough, however, you move your wall sheathing into the danger zone—above freezing and very humid.

We’ve learned from earlier studies how to use fiberglass and EPS and XPS foam in various wall systems to improve energy efficiency while avoiding moisture problems (See cchrc.org/safe-effective-exterior-insulation-retrofits). This latest study looked at how cellulose performed in different wall scenarios over an 18-month period. These were not standard walls—they intentionally lacked a vapor barrier because we wanted to force moisture into the walls.

Cellulose insulation is made primarily of recycled paper. As a local, rather inexpensive product, it has recently become more popular in building in Interior Alaska. “Dense-pack” cellulose is blown into a wall to a density of 3.2 pounds force per cubic foot, which is designed to prevent the insulation from settling over time. Dense-pack cellulose has an R-value (or insulation value) of 3.7 per inch—slightly higher than fiberglass batts and slightly lower than EPS foam.

Our study shows that cellulose can handle moisture better than fiberglass or EPS insulation when used properly. The test wall that used cellulose as both interior and exterior insulation maintained lower humidity levels (and was less likely to condense or grow mold) than the test wall that used interior fiberglass and exterior foam.

That can be partly attributed to material properties of cellulose. Dense-pack cellulose is actually less permeable to air flow than fiberglass batts. So when used as interior insulation, it reduces the amount of moisture that migrates into the stud cavity.

Cellulose also has the ability to absorb and release water vapor, allowing it to moderate moisture levels within a wall and prevent the large spikes in relative humidity that cause moisture damage.

It’s also more permeable to water vapor than EPS or XPS.  The test wall with exterior cellulose had lower humidity levels than the wall with exterior foam, because it allows faster drying to the outside.

Based on this study, dense-pack cellulose can provide a good option for exterior insulation beyond rigid foam board. In future studies we plan to look at the minimum amount of exterior cellulose needed to keep the sheathing warm and dry.

What is Timber Frame Construction

Photo Courtesy Dave Miller

Photo Courtesy Dave Miller

Timber frame homes are characterized by large structural wooden beams visible throughout the interior. Timber-frame construction techniques have been in use for hundreds of years throughout the world, initially brought to North America by European settlers.

The skilled craft of timber framing remained common practice until the early 19th century, at which point both milling and construction methods shifted to machines and mass production. Advances in technology, such as large powered circular saws, enabled mills to quickly produce large quantities of smaller dimensional lumber, which could be more easily transported. In turn, mass produced smaller framing members made it possible to erect a home with only a small team of builders using “stick frame” construction techniques that remain relatively unchanged to this day.

While timber frame construction is still in use, it has evolved from the purely practical construction technique that it once was. Originally, timber framing was primarily structural, however in today’s homes, timber frame construction is also used to showcase the aesthetics of the timber frame substructure, since it remains exposed towards the home’s interior.

Many different tree species can be used for a timber frame, including Douglas fir, Sitka spruce, Eastern white pine, red cedar, oak and Interior Alaska white spruce. The trees are handcrafted or milled into large beams.

In the United States, there are several suppliers who cut custom beams according to a computer-aided design plan sent to them by a builder.

At the building site, the beams are assembled into a structural frame that is fastened together with a combination of carefully fitted interlocking wood joints and wooden pegs and splines. In a traditional timber frame, metal connectors of any kind are seldom used. A completed frame will contain combinations of dozens of types of joinery that make it unique.

For instance, some substructures are built like wooden furniture, where the connecting beams use mortise and tenon joinery, a process through which two beams are cut so that one has a square or rectangle opening (the mortise) into which the other beam (the tenon) fits exactly.

Usually, joints of this type are held together with exposed wedges or pegs and have the additional benefit of great strength. (A similar construction technique, post-and-beam, uses metal braces and bolts to connect beams.)

After the timber frame substructure is erected, it is enclosed, often using structurally insulated panels (SIPS), to complete the home’s envelope. Most timber frames homes have open interior designs to showcase their exposed architecture. Plus, interior walls are not needed for structural purposes.

Timber frame homes come in all sizes, from small cabins to expansive homes. While timber frame construction tends to cost more than traditional stick-frame construction, the extra planning, materials, and labor results in a truly unique and durable home.

Today, timber frame construction fills both a practical and artistic role in the building community by crafting a home that is both a shelter and a work of art.

What are Structural Insulated Panels and considerations for Alaska

SIPsStructural Insulated Panels, or SIPs, are prefabricated building panels that combine structural elements, insulation, and sheathing in one product. SIPs can be used for the walls, roof and floor of a building in place of more traditional construction methods, such as stick-framing. A SIP typically consists of a foam insulation core with a structural sheathing panel bonded to both faces. Sheathing panels are usually made of industry standard OSB or plywood.

Building with SIPs

 

Constructing a home from SIPs begins at the design phase: builders must work with the SIP manufacturer since the panels are specific to the design. Once the plans are finalized, the SIPs are made and shipped to the job site. The panels are labeled so builders know exactly where each panel goes in the building.

As they are erected, the panels must be joined together according to manufacturer specifications. For instance, many panels are joined with splines that are secured with screws. When the structural connections between panels are being made, workers must take care to seal the joint between the panels to ensure it remains airtight. Air sealing the panel joints can be accomplished using sealing agents such as caulk, adhesive, mastic, spray foam or tape. A tight seal is also necessary in order to prevent moisture from entering the panel, which can lead to structural deterioration of the panel components over time. Some building inspectors may require a 6mil polyethylene sheeting vapor retarder be installed on the interior side (warm side) of the SIPs once the panel construction is completed.

SIPs2

Electrical outlets and wiring are usually installed into recesses and holes pre-cut into the panels, both on the interior and the exterior as needed. Any special considerations for running electrical systems or other mechanical penetrations through the SIPs should be addressed with the manufacturer during the design phase.

Benefits and Concerns

There are several potential benefits to building with SIPs. For one, the absence of an air permeable wall cavity prevents convective heat losses from occurring within the panels. Large panels will have fewer framing members than a stick-framed wall, which reduces heat losses due to thermal bridging. With a trained crew, SIP buildings can be erected quickly, a big advantage in climates with short building seasons. Properly constructed, a SIP panel home can realize a high level of air tightness and energy efficiency.

On the other hand, builders must take extra care to ensure proper assembly and sealing to prevent any problems due to moisture infiltration and air leakage. Builders also do not have much flexibility in on-site design changes, since panels come pre-cut. An experienced builder who can work through a home design with the manufacturer and who doesn’t cut corners with sealing panel joints is a necessity.

SIPs can be either cost-effective or cost-prohibitive depending on the situation. The design services and shipping costs may drive the price of SIPs above that of conventional framing materials. However, this can pay off in reduced labor costs if a trained crew erects a building quickly, or if several buildings of the same design are being erected.

Egress and Home Safety

MINOLTA DIGITAL CAMERAEgress is a means of emergency escape. Not surprisingly, all houses need egress for events such as a fire, and emergency egress is required by the International Residential Code for residential buildings. The IRC requires a form of egress in basements and rooms where people sleep. Each bedroom must have its own emergency exit.

While egress could be a door opening to the outside, it is most commonly a window, and the IRC specifies minimum requirements for egress windows. For one, an egress window needs to open to a public street, alley, yard or court. Also, the window must meet minimum size requirements so people can exit. The minimum size is 5.7 square feet, unless the windowsill is on the floor, in which case the minimum is 5 square feet. The window must be at least 2 feet tall and 20 inches wide. Meeting the minimum height and width requirements doesn’t guarantee meeting the minimum area, so the window will have to be larger in at least one of those dimensions.

Finally, the window cannot be more than 44 inches from the floor, and people must be able to open the window without any special tools or knowledge. Window coverings, such as a screen or bars, are OK, but people need to be able to remove them without any special force, tools or knowledge.

Basements are often located below grade, or below the typical ground level. Since egress windows in basements wouldn’t do much good opening to soil, a window well is required outside the window. The window well should be large enough for the window to open fully, and also should contain a ladder if the well is more than 44 inches deep. Of course, the IRC specifies well and ladder dimensions if this situation applies to your home.

Does your house have emergency egress? Some older homes built before the IRC requirements do not. A means of egress is sometimes overlooked during remodels — for example, converting a space to a bedroom that was not initially planned for that use. If you have a room that does not meet the minimum egress requirements, there are many reasons to correct the problem, the most important being providing a way to exit a house safely in an emergency.

Adding egress windows in required rooms will allow your house to pass inspection should you decide to sell it and will add value to the home as well. Sometimes, adding or replacing windows can become a major project, and it must be done correctly to avoid air leakage and drainage problems later. If you need to install egress windows, find a contractor familiar with the building code and who will take the time to properly install energy efficient windows that meet the requirements.

Valuing energy efficiency in the housing market

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The Alaska Housing Finance Corporation recently released a tool that could boost the appraised value of energy efficient homes.

The AK Appraisal Tool, developed by AHFC, the Cold Climate Housing Research Center and Alaska Craftsman Home Program, allows appraisers to add value to a home that performs better than comparable homes. The tool could promote energy efficient housing through making efficient homes more affordable and increasing their resale value.

Appraisers typically look at factors like square footage, number of bedrooms and aesthetic features like granite counter tops. If a house was super-insulated or used alternative energy sources, there was no accepted way to factor that into the appraised value. This tool provides a way to value energy efficiency based on the energy bills of a house compared to other similar houses in the area.

Here’s how it works

You log onto the site  and enter basic information about a house, including the community, the energy bills and at least two of the five following pieces: street name, number of bedrooms, square feet, rating points and year built. Our 1,800-square-foot test house was located in Fairbanks and had $6,000 in annual energy costs, including heating oil and electricity. The program then searches AHFC’s database of 105,000 housing units to find all comparable homes in the same area — in this case 85 — and calculate their average utility bills — $8,150. You can enter up to 10 other comparable houses (based on other appraisals). The program crunches all this information into the “net present value,” or the energy savings of the test house versus an average house during a 5-year period — $9,058. The appraiser can add up to that amount to the value of a home (all appraisals must be reviewed and accepted by the lending institution).

The program also provides the impact to the mortgage payment. In this example, if $9,058 were added to the home’s appraised value, it would increase the monthly payment by $44 (based on a 30-year mortgage at 4.25 percent). But remember, the homeowner is saving $2,100 per year, or $180 per month, in energy compared to an average house, so the overall savings far outweighs the bump in the mortgage payment. Plus, the resale value of the energy efficient house is higher.

There are benefits to the lending institutions as well. The fact that homeowners are spending less on energy every month increases their chance of making their mortgage payments. This reduces the lender’s risk of default and foreclosure.

How will it be used?

AHFC is already training lending institutions, builders and realtors to use the tool.  Builders could also use it to show clients the potential energy savings and increased appraised value of an energy efficient house.

Building workshops & classes this spring

While it might seem like summer is far away, the building season is right around the corner, and now is a good time to finalize any plans for upcoming home improvements. If you’re interested in reducing your home’s energy use, there are several opportunities this spring to learn about energy efficient building and retrofit techniques.

The building addition at CCHRC, which opened last year, features passive solar design, radiant floors, a pellet boiler and a super-insulated building envelope. There are efficient technologies in the original building as well, including a masonry heater, ground source heat pump, a sewage treatment plant, solar photovoltaic panels and thermal storage. Tours are offered at 2 p.m. on the second Thursday of every month and feature both the original building and the addition, and include plenty of time for questions and discussion, as well. Spring 2014 tours will take place Feb. 13, March 13, April 10 and May 8. In addition, the Builders Resource Library at CCHRC contains information on many aspects of cold climate construction and heating systems. The library is open Monday-Friday, and a catalogue is available online atcatalog.library.uaf.edu (select CCHRC from the Library menu).

Golden Valley Electric Association offers one-on-one instruction through its Home$ense audit program. Through the $40 program, an energy auditor visits your home to discuss ways to reduce your electrical usage and energy costs. To sign up, call the member services department at GVEA at 458-4555 or visit www.gvea.com.

Classes on more advanced topics are offered by the Alaska Craftsman Home Program (ACHP). Advanced Cold Climate Construction will be held Feb. 12 and 13 in Fairbanks, covering the latest energy efficient construction methods on topics such as insulation, vapor retarders, windows and ventilation. The class includes a construction manual and certificate for continuing education credits. Also, ACHP will

offer a one-day class on the Building Energy Efficiency Standard (BEES) on March 19 and May 22. This class covers the BEES requirements for insulation values, air leakage, moisture protection and ventilation. Fees and registration for these classes and more information can be found at www.achpalaska.com.

For those interested in wood heating, UAF is hosting the Firewood Workshop from 10 a.m. to 2 p.m. Saturday in the Bunnell Building. The workshop covers how-to tips for cutting and drying wood, operating a wood stove and more.

Finally, the annual Interior Alaska Building Association Home Show will take place March 28-30 at the Carlson Center and will feature topics including financing, remodels and new construction. There also will be seminars and demonstrations on a variety of topics related to homebuilding. The home show kicks off the summer building season in Fairbanks and is an excellent way to gather lots of information about energy efficiency.

What’s a GFI outlet and where should I use them in the house?

A ground fault interrupter outlet, or GFI outlet, is designed to protect people from electric shock. GFI outlets have three holes in a triangle pattern; there are two vertical slots and a round hole between them The shorter slot is called the “hot,” the longer slot is the “neutral” and the round hole is called the “ground.”

Typically, all electricity will flow from the “hot” slot through an appliance plugged into the outlet, and back into the “neutral” slot. The GFI outlet monitors the current flowing to and from the appliance. If the outlet senses an imbalance in the current flowing from the hot to the neutral slots, it will disconnect electricity flowing to the outlet. Most GFI outlets are very sensitive, and are capable of detecting a current imbalance of just a few milliamps.

Such an imbalance generally means there is a current leak somewhere-the worst case scenario being that the missing current is flowing into a human, instead of back to the neutral outlet. GFI outlets shut off current quickly, in less than one-tenth of a second, so that extra current will not flow where it’s not supposed to.

It can be difficult to know if you have GFI outlets in your home just by looking at them. They are recommended in areas of a building where there is water, because moisture increases the risk of electric shock (picture someone dropping a hairdryer into the sink). A few decades ago, they generally were only installed around pools and boathouses, but now are commonly found (and required by building code in Alaska) in places like bathrooms, garages, kitchens, crawl spaces, unfinished basements and outdoor outlets.

Heat tape should be plugged into a GFI outlet because heat tape is typically protecting water pipes and therefore has the potential to be exposed to moisture.

Some GFI receptacles have test/reset buttons on them. You can check if the GFI protection on these outlets is working by pushing the test button — which should shut off the current to any device plugged into the outlet. Pushing the test button will also cause the reset button to pop out. You can turn the outlet back “on” by pressing the reset button. GFI outlets can fail as power surges from the utility can damage their internal circuits, so testing them occasionally is a good idea.

Other outlets have GFI protection at an “upstream” outlet or at the distribution panel and may have no test/reset button. In this case, to test a specific outlet, you will need to push the test/reset buttons on the upstream outlet or at the distribution panel.

Installing GFI outlets

It’s just as easy as installing a regular outlet, though you need to pay attention to ensure the proper terminals are connected to the source. It takes a little extra consideration to wire it up if you are using it to protect outlets downstream.

GFI outlets cost more to install than regular outlets. While a regular outlet can cost as little as a few dollars, GFI outlets can cost more than $20. This adds up when considering every outlet in a home and explains why electricians may install GFI protection at the panel rather than at each individual outlet.

A similar type of outlet is an arc fault circuit interrupters (AFCI). These are required in the living room, bedrooms, hallways, at lighting circuits, and use a special circuit breaker at the distribution panel. While GFIs are designed to protect you from shock, AFCIs are designed to prevent fires when an electrical arc is caused by, for example, driving a nail into the wall and hitting a wire. GFI receptacles cannot be used on an AFCI circuit.

How to prevent mold growth in your home

Mold requires moisture, above-freezing temperatures, oxygen, and nutrients to grow. The nutrients can come from many building materials such as the paper facing on drywall or wood. Mold spores enter a home through open windows and doors, on the clothing and shoes of people, or in the fur of a pet. As mold spores are assumed to be present in most environments, they easily can enter a home. If spores land on a surface with available nutrients and moisture, they can grow into a colony.

Preventing mold growth usually is focused on controlling moisture, since above-freezing temperatures and oxygen also are required by the house’s human occupants. In homes, water leaks and condensation are the primary sources of moisture that lead to most mold growth. Examples of water leaks would be a break in the building envelope, such as a hole in the roof that allows rain to enter, or a plumbing leak. Condensation occurs when humid air encounters a cool surface, such as the windows in an exterior wall. When air containing water vapor cools to the dew point, it can no longer hold as much moisture and that excess moisture is then deposited on the adjacent cool surface in the form of water droplets. Air with high humidity is common in bathrooms and kitchens because cooking and showering expose the surrounding air to substantial amounts of water. However, plants, aquariums and even breathing contribute to the humidity level in a home.

Preventing mold growth

Keeping indoor humidity levels low is a big step towards preventing mold growth. Although indoor humidity that ranges between 40 and 60 percent at room temperature is best for human health, the reality is that in an extreme cold climate with temperatures below -20°F (such as Fairbanks), levels of more than 30 percent can lead to condensation forming on cooler surfaces such as windows, exterior walls behind furniture, and in closets. Indoor humidity levels between 20 and 30 percent are much safer in terms reducing the condensation risk during winters in Fairbanks, especially during very cold periods. However, this will vary depending on the insulation level of your home. Humidity levels lower than 30 percent can be tolerated by humans, however a greater percentage of occupants may experience the physical discomforts associated with drier air. To measure the humidity level in your home, you can buy a hygrometer at a hardware store or online for between $20 and $60. To prevent humidity from reaching damaging levels and maintain healthy indoor air quality, tight houses will require ventilation systems, such as exhaust fans in bathrooms and kitchens or a whole-house Heat Recovery Ventilator (HRV).

Even homes with a low overall humidity may have damp microclimates where mold can grow. Inspect areas such as crawlspaces periodically. A crawl space can produce large quantities of water vapor if damp soils aren’t covered with an intact and well sealed vapor retarder. In the crawlspace be on the lookout for water leaks, air leaks in ducts, or condensation on pipes, concrete or discolorations on wood surfaces — particularly around the rim joist area. Be sure to address any issues promptly. If there is standing water as a result of a leak, you have 24-48 hours to dry the area before mold spores can settle in and grow, so clean up the water as soon as you can, and then use a dehumidifier or fan to help dry out the area.

Damp areas on walls can be eliminated by making sure there is air an air space and good circulation between the wall and any furniture, clothing, or other objects. Firewood drying indoors also can contribute to moisture loads. A plugged or disconnected dryer vent can introduce large amounts of water vapor into the air and go unnoticed. Inspect all vents to the exterior periodically to ensure they are in good working order. Eliminate any standing water in the home. You can prevent standing water in showers and sinks by keeping drains clear and clean. Keeping a pot or kettle full of water going on the stove should be avoided.

Finally, if you do discover mold growth, it is important to clean it up as soon as possible to stop the mold from spreading and to prevent further occupant exposure.

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

hopper.

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.