Making Houses Work

Promoting sustainable shelter in Alaska


Moisture Performance of Cellulose Insulation

August 13th, 2014
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

July 24th, 2014
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 is an Arc Fault Circuit Interrupter?

July 7th, 2014

An arc fault circuit interrupter, or AFCI, is designed to detect dangerous electrical arcs and disconnect power to the circuit before a fire starts.  They contain current and temperature sensors as well as a microprocessor that can distinguish arc faults caused by unintentional electrical hazards.

An arc fault is the unintentional flow of electricity between two separate wires.  This electrical discharge can create enough heat to further break down electrical insulation and start a fire, especially if nearby objects are flammable, such as a wooden floor, wall or piece of furniture.  For instance, an arcing fault might occur in a power cord that has been damaged (for example, crushed beneath a piece of furniture).  The damaged insulation could enable electricity to jump across to a neighboring wire within the cord and build up enough heat to start a fire. Arcing faults can also occur in power cords where the insulation has cracked due to age – or in electrical wires inside a wall that have been accidentally pierced by a nail.

According to the Electric Safety Foundation International, arcing faults are responsible for 30,000 home fires each year in the United States. These types of fires can be prevented by installing AFCIs. In new homes, AFCIs are now required in the living room, bedrooms and dining room.

There are three types of AFCIs.  The most common, a branch AFCI, replaces standard circuit breakers in your home’s service panel. Branch AFCIs can detect an arc-fault in the circuit from the panel to the outlet and thus will shut off electricity to that branch circuit. Outlet AFCIs provide arc-fault protection to devices plugged into that outlet.  Combination AFCIs are a more advanced technology that can detect additional kinds of faults, such as an arc within a single wire due to a loose connection.

Does your home have AFCIs?

You can check to see if your home has AFCIs by looking at the outlets and the circuit breakers.  An AFCI outlet and circuit breakers will be labeled as such and have a TEST button on them.  AFCIs are not to be confused with ground fault circuit interrupters (GFCIs), which also have a TEST button. GFCIs are another type of electrical safety device that detect current imbalances caused by a current leak, which can occur in the case of electric shock. They are required in bathrooms and kitchens and are often installed in other locations with water exposure, because moisture increases the risk of electric shock.

GFCIs protect people from electrical shock and AFCIs protect structures from fires.  If you have AFCIs installed, they can be tested by pushing the TEST button. If the circuit trips, then the AFCI is working.  To reset the AFCI, first turn the breaker to the OFF position. Then you will need to flip the breaker back to ON.  If the circuit does not trip, the AFCI should be replaced.  AFCIs can be installed by a licensed electrician and typically cost less than $50.

For more information about AFCIs and other electrical safety devices, visit the Electrical Safety Foundation International’s websitewww.esfi.org .

What are indoor “pollutants”?

July 7th, 2014

Ventilation receives more attention these days because houses are more airtight and better insulated than ever before.  While this saves on heating costs, it also means that passive air leakage through the building envelope will not provide sufficient ventilation. Mechanical ventilation systems, such as exhaust fans or HRVs, are needed to flush out pollutants and provide fresh air to occupants.

Pollutants can be introduced into a home in many ways – people breathe out carbon dioxide, heating appliances can produce carbon monoxide, radon can leak in through the foundation, and dust can blow in through a door or window.  Pollutants are also produced in kitchens, one reason for installing range hoods above stoves.

What pollutants are produced in kitchens?

Cooking is a source of both moisture and odors.  Both of these are good in small doses – water vapor helps to maintain higher indoor humidity during dry winters and smells can entice the family to a common place.  Excess humidity, however, is conducive to mold growth.

Gas burners release gases directly into a home, and they can reach harmful levels if not exhausted.  Nitrogen dioxide, which can cause respiratory problems, is produced as a result of gas combustion. So is carbon monoxide, a colorless, odorless gas that reduces oxygen delivery to organs and can be very harmful—and even fatal—to humans. If you have a gas burner, it’s a good idea to have a carbon monoxide detector in your kitchen, in addition to ventilation.

All cooking appliances also produce small airborne particles, including particles under 2.5 micrometers in diameter that can enter lungs and cause respiratory problems. An extreme example of this (and one you can smell) is when you turn on a heating appliance that has been off for a long time, such as when you use a toaster that hasn’t been used in months. Finally, certain cooking methods and foods can result in other harmful pollutants. The most common is acrolein, which many people will recognize as the acrid smell of burnt fats, such as cooking oil.

What is effective kitchen ventilation?

First, effective kitchen ventilation will depend on the amount and type of cooking that you do.  Boiling water for mac and cheese every once in awhile will not produce as many pollutants as pan frying steaks during on a Saturday night in a restaurant.  Of course, most homes fall between these two extremes. Consider your cooking habits when choosing a ventilation strategy.

Range hoods are your best option for kitchen ventilation and come as stand-alone systems or can be integrated into other kitchen appliances, such as microwaves. They should be turned on every time you cook. Range hoods can vary in performance, so it is important to ensure that your system provides sufficient ventilation for the type and volume cooking that you do. Also, range hoods must actually exhaust air outside a home rather than just circulate air through a grease trap. Ideally the range hood should also extend over all burners of the stove. In the summer, opening a window can also help with ventilation.

Whole house ventilation systems such as HRVs also help provide adequate ventilation for your house while cooking, as it’s common for range hoods to capture only a fraction of the pollutants released.  One option is to use a boost mode for the HRV while cooking.  If you do use an HRV for kitchen ventilation, be careful that the HRV is not in recirculation mode (which circulates air through a home but does not exhaust air outside and bring in fresh air) during cooking times.

How much can I save with a programmable thermostat?

July 7th, 2014
Programmable thermostats are an easy way to potentially save hundreds of dollars a year on heating.

Programmable thermostats are an easy way to potentially save hundreds of dollars a year on heating.

Many of us use programmable thermostats to reduce the indoor temperature when we’re sleeping or away at work. These devices are relatively inexpensive to install and can save energy by automatically reducing the amount of heat provided to the home when you’re away and then returning the house to a comfortable temperature when you return.

The amount of energy and money saved by a programmable thermostat depends on a lot of factors: insulation levels, efficiency of heating equipment, and the typical indoor temperature all can affect potential savings. CCHRC modeled a typical Fairbanks home to estimate the savings from installing and properly setting a programmable thermostat. The modeled home is 1,840 square feet, has insulation levels typical of a home built in the 80s and 90s and uses an 80% efficiency oil-fired boiler. The thermostat is typically set at 70 degrees.

Over the course of a year, 16 gallons of fuel oil were saved for every one degree that the temperature was set back in this modeled home. This assumes that the temperature was reduced for 12 hours a day when the occupants were away or asleep. So, for example, a homeowner who programmed their thermostat to turn the heat down from 70 to 60 degrees for 12 hours while they were sleeping or away is estimated to save approximately 160 gallons of fuel oil over the course of a year–around $650 at today’s prices.

How can such a small temperature change save so much?  The key is that it happens every day throughout the year.  As a comparison, over the course of a year, the average annual temperature in Fairbanks is only about 10 degrees cooler than the average annual temperature in Anchorage– a few degrees each day can make a big difference.

Not everyone will see such large savings.  People with more energy efficient homes use less fuel, and thus stand to save less money from using a thermostat.  It’s also important to properly program the thermostat–recent research has shown that while people can save significant amounts of energy with programmable thermostats, many people see no savings because they haven’t properly programmed the devices.

For the average home in Fairbanks, programmable thermostats are a simple, cost-effective, painless way to lower your energy bills.

What are Structural Insulated Panels and considerations for Alaska

April 24th, 2014

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.

CCHRC Creating List of Preferred Energy Auditors for Fairbanks Nonprofit Retrofit Pilot

April 23rd, 2014

CCHRC is pleased to announce that it is creating a list of preferred energy auditors to perform audits as part of the Fairbanks Nonprofit Retrofit Pilot project.  Qualifying energy auditors in Alaska are invited to apply at www.cchrc.org/fnrp.

The pilot project connects the nonprofit community with financing to enable energy efficiency retrofits. CCHRC will evaluate the process and outcomes of this model to better understand several factors: the extent to which financing can replace grant funding for energy efficiency audits, the extent to which program delivery is enhanced through reduced energy costs, and the extent to which partnerships with the nonprofit sector are necessary to advance energy efficiency retrofits from audit through construction.

Egress and Home Safety

April 18th, 2014

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

April 10th, 2014

REMOTE_pat
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.

Thermal mass and passive solar design

March 19th, 2014

In construction, thermal mass refers to heavy, dense building components with a high capacity to absorb, store and release heat, for example—logs, masonry, concrete and adobe.  These materials are used in the building envelope to provide structure, but their thermal properties mean that they can also provide other benefits. In this first article of a two-part series on thermal mass, we’ll address how thermal mass can be combined with passive solar design to reduce building heat and cooling load.  Next week we’ll examine the effect of thermal mass for more conventionally designed homes in three different locations.

Passive solar design uses a combination of building features along with the sun’s energy to provide heating in a home.  Typically, a home’s orientation combined with south-facing windows and a large thermal mass are designed to collect, store and distribute solar energy during the heating season. During the summer, features such as deciduous trees or awnings can block solar energy from entering a house and causing overheating. Many homes in Alaska use passive solar design to provide part of their heating needs during the year.

In passive solar design, there is no control system that dictates the movement of heat energy, as with a boiler or furnace.  To understand how this might work, picture a house with a concrete floor in a south-facing room on a sunny spring day in Fairbanks.  As sun’s radiation enters the room through the windows, it warms up the room and the thermal mass of the concrete floor absorbs this energy throughout the day.

ThermalMass_graphic

At night, the situation reverses.  With no incoming solar radiation, the heating system will need to work to keep the temperature of the room at the set point. However, as the room’s ambient temperature drops below the temperature of the thermal mass, the stored heat energy in the massive floor radiates back into the room, stabilizing the temperature and delaying when the heating system needs to switch on. In effect, the thermal mass acts as a heat battery, storing solar radiation until the sun disappears and then releasing it back into the room. A properly designed passive solar system can result in energy savings for a home because the thermal mass can store excess heat during the day and allow it to offset nighttime heating loads.

Although thermal mass is often in the form of a concrete floor, there are other ways to incorporate it into a home—such as a wall that receives lots of sun or a masonry bench or shelves in the sun’s path.

As the days lengthen during the spring and summer, the large south-facing windows in the above example can allow too much solar radiation to enter a room and cause it to overheat. Some people install awnings or curtains, or plant deciduous trees to shade the windows. Thermal mass also helps prevent overheating, especially in early spring before deciduous trees have leafed out.  A room that might have become uncomfortably warm during the day instead experiences less rise in temperature as the solar radiation is absorbed by the thermal mass. This energy is released later in the evening when outdoor temperatures are cooler. Overall, the thermal mass acts to smooth out temperature swings in the room, enhancing indoor comfort.