Tag Archives: energy efficiency

Vapor Barriers and House Wraps: where and why?

House wraps must stop bulk water from entering on the cold side and also be permeable enough to allow water vapor to pass through from the warm side.

House wraps must stop bulk water from entering on the cold side and also be permeable enough to allow water vapor to pass through from the warm side.

The building envelope is defined as those parts of a house that keep the indoor and outdoor environments separate. The building envelope includes the exterior walls, roof, windows, doors and the foundation and/or ground floor.

As elements of the building envelope, vapor barriers and house wraps are a critical part of controlling moisture and air flow through your home.

If selected and installed properly, these products can help you conserve energy, prevent mold growth and maintain the structural integrity of your home. On the flip side, not using these products or using one incorrectly can have the opposite effect.

Vapor barriers on the warm side

A vapor barrier, also known as a vapor retarder, is a layer of material designed to slow or nearly block the movement of water vapor by diffusion. How much a vapor retarder impedes the movement of water vapor is referred to as its permeability rating, or “perm” rating.  Six-mil-thick (0.006 inch) plastic sheeting is a typical vapor retarder material prescribed by residential building codes in cold climates, as its perm rating is extremely low.

In standard cold climate frame construction, the plastic vapor retarder is located on the warm-in-winter side of the wall — typically it is applied over the studs directly behind the drywall.

All homes contain moisture inside — cooking, bathing, breathing all create water vapor. In winter time the challenge then becomes keeping this water vapor from reaching places in the building envelope where it can condense.

Ventilation, which is essential to exchange moisture-laden air with clean, dry air, helps reduce the quantity of moisture in a tight home, but not enough to eliminate the need for a vapor retarder.

Where it gets interesting is that 98 percent of water vapor in a home travels by air leakage, while only the remainder moves by diffusion — through solid materials such as the drywall and sheathing in your walls. So, with proper sealing around penetrations and by sealing overlapping layers, we can also rely on the plastic vapor retarder to serve as an air barrier.

House wraps on the cold side

House wraps, on the other hand, are primarily designed to cope with the elements on the outside. They must be permeable enough to allow water vapor to pass through them from the warm side, but still stop bulk water like rain from entering on the cold side — similar to a Gore-Tex jacket.

By nature, house wraps must be vapor permeable enough to allow for drying if moisture finds its way into the wall cavity from either the inside or the outside. In addition, house wraps can help minimize the movement of air in and out of the exterior walls. Air movement through the building envelope in an uncontrolled manner, means you’re losing heat, which can become a burden on your budget.

To effectively repel water and reduce airflow, house wraps must be detailed correctly and applied using the manufacturer’s recommended methods and adhesives. All the penetrations into your walls from the exterior, such as vents, electrical connections, and architectural features, must be carefully accounted for.

The right types of house wraps can perform an important job in windy places by stemming significant heat loss and keeping the framing protected from precipitation that gets past the siding.

Final thoughts

The placement and permeability of vapor barriers and house wraps are addressed by building codes, but vary by region. Vapor barriers are required on the warm-in-winter side of the exterior walls in Fairbanks.

This article only touches on the details required to choose and install vapor barriers and house wraps. Placement and water vapor permeability can be a fairly complicated issue because of the wide variety of products on the market today.

You can find resources at CCHRC, the University of Alaska Fairbanks Cooperative Extension Service, and your local building department to help you make the right decisions. Doing your research up front will help maximize home performance and prevent problems later.

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

How can I keep moisture and ice from forming on my windows in the winter?

Windows can be a barometer for how much humidity is inside the home.

On really cold days, you might notice condensation forming on the inside of your windows. This can be caused by one or a combination of factors: excess humidity, inadequate ventilation, or poor windows. To understand and correct a particular issue in your home, you need to know some basic properties of moisture.

Condensation occurs when water vapor (a gas) turns into water droplets as it comes into contact with a cold surface. The point at which this happens depends on the temperature and humidity of the inside air. The warmer the indoor air, the more water vapor it can “hold,” and moisture can better remain in the vapor state. When air moves next to a cold window, the temperature drops and it can’t “hold” as much vapor.  That’s when you start to see condensation forming.

For example, if the indoor temperature is 70 degrees and the outdoor temperature is 0, then moisture will begin to condense on a single-pane window when there is roughly 15 percent relative humidity in the house. A double-pane window will cause condensation at around 25-40 percent relative humidity, and a triple-pane window at between 30-50 percent.  These are rough numbers are based on average window insulation values.

The recommended indoor humidity levels for occupant health and comfort range from 30-50 percent. The general rule in a cold climate, however, is to target the lower end of this spectrum due to the risk of condensation within walls and ceilings. If your house has adequate mechanical ventilation, humidity is less of a concern. In Fairbanks, it’s tough to maintain anything close to 50 percent humidity in a properly ventilated house, because the winter air is so cold and dry.   Because of its low moisture content, the inherent dryness of Fairbanks winter air is good for homes but not always the occupants, since discomfort related to the dryness can be problematic.

What can I do about it?

Three things: make sure your home is properly ventilated, aim for less than 40 percent relative humidity to keep both you and your home healthy, and consider replacing your windows or adding moveable window insulation during cold months.

If you already use mechanical ventilation and have low interior humidity, but are still having problems, you may need to examine your ventilation setting. If you have a heat recovery ventilator (HRV), it may be recirculating too often, which can contribute to increased moisture build up in the air. Recirculation mode closes the connection to the outside and brings exhaust air back into the rooms.  Recirculation mode keeps the HRV core defrosted and saves energy, but it is also possible for it to run for too long.  Some experimentation with the HRV settings may be necessary.   For example, in 20/40 mode the HRV brings in fresh air for 20 minutes and then recirculates for 40 minutes, and likewise for 30/30. If you’re getting condensation in your current mode, try decreasing the amount of time the unit recirculates.

Also make sure air is allowed to circulate—either passively or mechanically—throughout the entire house. If you close the door to the bedroom, the air can become cold and moist enough to condense on windows.

Older, poorer performing windows can create problems no matter what you do to your interior air. Bad seals around operable windows, metal spacers between the panes, and inadequate insulating value can cause the window surface to get cold enough for condensation to occur.  If you’re not ready to invest in new windows, consider some type of moveable window insulation like foam board (on the outside) or well-sealed plastic film (on the inside). A CCHRC guide to different types of window insulation can be found at http://www.cchrc.org/evaluating-window-insulation.

Energy Use & Savings Potential in Public Buildings

A new white paper by the Alaska Housing Finance Corporation gives the first in-depth picture of the energy use of public buildings in Alaska. By looking at comprehensive energy audits of 327 out of an estimated 5,000 public facilities, CCHRC researchers found that the average building can save $25,000 per year on energy just by modest investments in efficiency.

That adds up to $125 million annually in taxpayer savings. Many of these upgrades are easy and affordable.

Some examples found by AHFC energy auditors include adding occupancy sensors to lighting and ventilation systems, programming thermostats to lower the heat when buildings aren’t occupied and using digital controls to avoid over-ventilating building zones. Energy auditors also found many zero-cost ways to save energy by fixing operational issues such as turning off heat tape in the summer and shutting off backup pumps when they’re not needed.

The report shows Fairbanks buildings are the most energy efficient in the state, while the North Slope, Anchorage and Southeast (outside of Juneau) were the least energy efficient.

Surprisingly, there was no correlation between the cost of energy in a given community and the performance of buildings. In fact, many of the same types of buildings in the same climate consumed vastly different amounts of energy, highlighting differences in construction and operation.

“That’s further evidence that many building managers don’t know how their buildings are performing, because they’ve had no one to compare themselves to,” CCHRC researcher Dustin Madden said.

This report provides facility managers with reference points in their climate and region, and gives tips from energy auditors on saving energy.

While the paybacks of energy improvements are often quick, funding can still be a challenge. Some organizations apply for legislative grants, bonds or funding from the Alaska Energy Authority.

AHFC has a $250 million revolving loan program specifically for state and municipal buildings to invest in energy retrofits. A portion of the energy cost savings are used to repay the loans.

Before now, little was known about the energy use of public facilities statewide. Understanding the performance of these buildings is the first step toward improving it. This research lays the groundwork for future policy decisions, changes in building design and education for facility operators and owners.

The public building audit project was led by AHFC and supported by federal stimulus funds. It included more than 40 auditors and engineers statewide. The recently published white paper on the findings was pulled together by the project leads, with Richard S. Armstrong as lead author and editor. Other contributors to the white paper were Alaska Energy Engineering LLC, Central Alaska Engineering Company, Nortech Engineering Inc., Renewable Energy Alaska Project and the Cold Climate Housing Research Center.

The report is available at: http://cchrc.org/docs/reports/Energy_Use_PublicFacilities.pdf.

Opening of the UAF Sustainable Village Wednesday, Oct. 3

The UAF Sustainable Village is a community for students who are passionate about the environment and reducing their carbon footprint. It is a collaboration between the UAF Office of Sustainability and the  Cold Climate Housing Research Center  to build and research energy efficient housing, renewable energy, and innovative heating and ventilation systems. Students at the Village make a commitment to sustainability through monitoring the systems, conserving energy and water, and helping develop additions like a greenhouse or community center.

On Wednesday we will celebrate the opening of the Village with a ribbon cutting on-site and words by CCHRC President Jack Hebert, UAF Chancellor Brian Rogers, student workers and student residents.

For more info contact Molly Rettig, Communications Coordinator, at molly at cchrc.org.

Wednesday October 3, 2012 at 12 p.m.


11:30—Press invited to tour the interior of a student home

12:00—Ribbon cutting & brief words by Chancellor Brian Rogers & Jack Hebert

12:15—Move to CCHRC for brief ceremony—student posters on display

12:30—CCHRC President/CEO Jack Hebert welcoming

12:40—Words from student on design/construction team – Skye Sturm

12:50—Words from student resident

1:00—Time for interviews

1:15-1:30—Optional public tour of a student home

What to look for in an energy efficient house

Shopping for a home in Fairbanks can be difficult, especially if energy efficiency is a priority. With heating oil prices volatile and resale value at stake, finding the most fuel-efficient home makes sense.

Following are just a few of the things to look for in an efficient home.

Site Location

  • South-facing slopes that are exposed to sunlight will be warmer in the winter and require less heating than comparable homes on north-facing slopes or obscured by dense tree canopies. Deciduous trees, such as Alaska birch, are desirable because they lose their leaves in winter and allow sunlight to shine through.
  • Ideally, homes should be situated lengthwise east to west in order to take advantage of the sun.
  • Protection from wind, provided by trees or hills, can help to conserve heat in winter. Low-lying evergreens or shrubs placed on the sides of a house that are exposed to wind will also help conserve heat.


  • Houses that share common walls with other structures, such as townhomes, lose less heat than standalone homes.
  • The overall shape of the house will affect heat loss due to the amount of wall space exposed to the elements. L-shaped, H-shaped, or U-shaped homes, for example, will tend to lose more heat than rectangular homes.

  • Arctic entryways that are sealed from the outside and the inside living areas by separate doors can help retain heat.

  • South-facing windows are preferable to windows on any other axis because they can collect sunlight and minimize heat loss.

  • Plumbing should be run inside heated or indirectly heated areas and consolidated as much as is practical. Sinks, baths, and laundry should be close to the water heater to minimize standby heat loss or, alternatively, on-demand water heaters can be used.



  • There’s a saying among energy raters in Alaska – “You can’t over-insulate, you can only under-ventilate.” When inspecting a house, ask how much and what type of insulation is in the floor, walls, and attic. Other than airtight construction, no other single factor will affect a home’s energy use more than insulation. But insulation without adequate ventilation will invite moisture problems.

  • All gaps and cracks in the house should be well sealed or caulked.

  • Doors and windows need effective weather-stripping.

Mechanical Systems

  • The performance of heating appliances such as boilers can vary widely and replacing an aging existing system can be expensive.  It’s not uncommon for heating systems to be oversized in relation to a homes energy needs, which can also contribute to efficiency losses.  Consider having the heating system professionally inspected to assess reliability and performance.
  • Doors and windows need effective weather-stripping.

  • Previous years’ fuel bills can help gauge heating costs, but be aware that the presence of a woodstove, pellet stove, or other heating appliance other than the boiler can make heating oil usage numbers misleading.

Home Inspections

  • Check to see if the home has already had an energy audit done.  An energy audit will provide a detailed assessment of the home’s energy performance and will help identify problem areas.  If energy efficiency is a priority, an audit/home inspection by a state certified energy rater can provide valuable insight into a home’s real world performance.


The paybacks of energy efficiency investments

The state of Alaska invested an estimated $110 million from 2008 to 2011 on extra insulation, new boilers, air sealing, and other retrofits for roughly 16,500 homeowners—about 10 percent of all homeowners in Alaska.

The Home Energy Rebate Program provides funding to help homeowners make their houses more energy efficient. CCHRC recently worked with the Institute of Social and Economic Research to look at the economic impacts of the program. The study, funded by the Alaska Housing Finance Corporation, showed homeowner investment, fuel savings, payback periods, job creation and more. Here are some highlights:

· Total spending for energy efficiency improvements was about $185 million, with state rebates covering 60 percent and homeowners 40 percent. Homeowners should recoup their investment in roughly 3.5 years. State and private spending will be returned in homeowner savings in less than 9 years.

· Annual fuel use dropped an estimated 33 percent for households who participated. The average homeowner will save an estimated $1,300 a year on fuel (or 26 percent).

· Every $1 million in state spending generated 12 Alaska jobs—7 direct retrofitting jobs and 5 indirect jobs—amounting to about 1,330 jobs.

· Overall, participants are saving an estimated $22 million annually. If they spend those savings locally, every $1 million in new household spending generates 11 jobs throughout the state economy—an annual average of about 240 jobs.

· The biggest money savers were more efficient boilers or furnaces (constituting 50 percent of energy savings). Adding extra insulation to walls, doors, and ceilings made up 25 percent of savings; sealing air leaks accounted for nearly 15 percent of savings; replacing windows and water heaters comprised 10 percent of savings.

· Anchorage homes made up 49 percent of retrofits; other Southcentral communities 27 percent; Fairbanks 14 percent; and Juneau 6 percent.

The full snapshot is available here.

*Changes in fuel costs and savings are estimates from AHFC’s energy-rating software as actual household heating bills aren’t currently available.

How does user behavior make a difference in my home’s efficiency?

Many people focus on the building envelope – the amount of insulation in the roof, the R-value of the walls, how many panes the windows have. Others think first of appliances – is the refrigerator certified as an ENERGY STAR appliance? What is the efficiency of the boiler? Does the hot water heater have a high energy factor? Are the lights incandescent bulbs, LEDs or CFLs?

Certainly all of these things have a role in making buildings energy efficient. However, there is an even more important factor that is often overlooked–the behavior of occupants. An oft-repeated saying in the building industry is “There is no such thing as a zero-energy home, just zero-energy homeowners.” Efficient buildings can’t reach their full potential if residents have energy-intensive habits. On the other hand, inefficient buildings can see large performance improvements just by changes in residents’ habits.

There are two main parts to energy efficient behavior: the types of appliances you buy and the way you use them. For example, do you own a large-screen plasma TV or a modest one? Both your consumer decisions and pattern of use play into your personal energy efficiency. For example, if you buy a 15-watt CFL floodlight and keep it on all the time, you may still actually use less than a 75-watt lamp that you turn off when not in use.
When it comes to your habits, remember what your mom and teachers probably used to tell you: Turn off lights when leaving a room; don’t leave the faucet running when you brush your teeth; take shorter showers; and put on a sweater instead of turning up the thermostat.

Changing habits can be difficult or uncomfortable, however, so there are also other options.

Many behavior elements can be addressed with technology:
· If you constantly forget to turn out the lights, or find yourself leaving on an outdoor light for hours while waiting for a spouse to come home at night, consider installing lighting controls. Motion sensors that can turn on and off lights are available for as little as $30 at home improvement stores.

· Programmable thermostats can be used to turn down the set temperature automatically while residents are away at work or asleep, and turn up the set temperature when residents are at home and awake. They can be programmed in 5 minutes – and offer savings on heating bills throughout the winter with no extra work.

· Do you have a number of devices plugged into the wall (phone chargers, TV, computer, etc.)? These devices draw a small baseline amount of current, called a phantom electrical load, as long as they are plugged in – even when they are turned off. Remembering to unplug everything can be difficult, but there are solutions. Plugging everything into a power strip means you only need to turn off one switch. Also, a smart power strip will shut off the current to peripheral devices such as a monitor and speakers when a central device, like a computer, is turned off.

· Do you have an electronic calendar on your phone or attached to your email? Use it to add automatic reminders for maintenance tasks, such as the yearly check-up on your heating appliance, or changing filters on a forced air distribution system. Remembering basic maintenance tasks improves the efficiency of equipment and prevents breakdowns.

· If you need to replace an appliance anyway, consider purchasing an Energy Star-rated one.

How else can you make your home more energy efficient? Go to www.cchrc.org or the website or Golden Valley Electric Association (http://www.gvea.com/resources/save) for more ideas.

Other resources on saving energy:

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.

Bethel school harnesses resources to save money

CCHRC is working with an education center in Bethel to help improve the energy performance of its new building.

Yuut Elitnaurviat is a vocational center that offers training in construction, health care, dental health aid, and other subjects for residents of the Yukon-Kuskokwim Delta region.

The new building at Yuut Elitnaurviat campus consumes more than 40 percent more than the average building in Alaska.

The school is spending more than 40 percent more than the average commercial building in Alaska for heating and power at its facilities—which includes a classroom, admin offices, a cafeteria, dormitory and shop—and the building is only a few years old. This stems from inefficiencies in heating, lighting, and ventilation systems, among others. For example, the air handling system is consuming more than its fair share of energy use and may be oversized for the building. In addition, the school is paying to heat much more domestic hot water than it actually needs.

CCHRC researchers visited the campus in March to explore options for improving the building’s performance.

“They’re paying almost 50 cents a kWh, and they’re using around 32,000 kWh a month, so it makes more economic sense to focus on the electric load than on space heating at this point,” said CCHRC research engineer Bruno Grunau.

CCHRC prepared a feasibility study of the local resources and found both wind and solar photovoltaic systems would be viable technologies. Researchers are now helping school officials plan a small wind farm and solar array. The wind farm could include up to 4-5 turbines, each producing approximately 6,000-10,000 kWh per year, and a 10 kW PV array that would produce approximately 8,500 kWh a year.

Building officials are also pursuing a commercial energy audit to find other economical ways to save energy, such as tightening the building envelope or installing high-efficiency lighting and daylight sensing.