Tag Archives: alaska

How does the recirculation mode on an HRV work, and is it safe in a cold climate?

We often stress proper ventilation as the key to maintaining a healthy indoor environment in a home, and promote heat recovery ventilators (or HRVs) as the best option for energy efficient ventilation in a cold climate.

HRVs exchange stale indoor air with fresh outdoor air, capturing heat from the outgoing air to pre-heat incoming air. They exhaust excess humidity, carbon dioxide, and indoor pollutants from pet dander, cleaning supplies, offgassing furniture, and other sources. The role of the HRV becomes increasingly important as homes are built tighter to save energy, which cuts down on passive air exchange.

To maximize the benefits of having an HRV, it helps to understand the different operation modes. One of the often-debated modes included in most HRVs in the United States is the recirculation mode. This mode is not often used in Europe because it is believed that the health risks outweigh the energy benefits. This article provides a description of the recirculation mode and gives pros and cons for the house and its occupants.

Under normal operation, the HRV replaces moist indoor air with fresh outdoor air. While HRVs recover much of the energy from the heated air during winter months, a considerable amount of heat is still lost due to the frigid temperatures in the Interior Alaska. In addition, extremely cold outdoor air contains virtually no moisture, which can result in very low humidity levels indoors—a negative for some homeowners.

In recirculation mode, the unit closes the connection to the outside and brings the exhaust air back into the rooms. This saves a lot of energy, since there is no cold air coming in from outside. On the other hand, moisture and indoor pollutants are no longer being flushed out of the home, and their concentration will continue to rise and can eventually reach harmful levels. Recirculation can also spread unwanted smells from more to less polluted areas, such as from the bathroom to the living room.

In order to maintain sufficient air exchange, HRVs offer modes where these two strategies can be combined. For example, 20/40, 30/30, or Smart Mode. In 20/40, the HRV will bring in fresh air for 20 minutes and then recirculate for 40 minutes (likewise for 30/30). Smart modes usually require some kind of sensor (humidity or carbon dioxide) to dictate when to ventilate and when to recirculate, based on which measurements the HRV controller decides is more relevant at any given time.

The major advantage of recirculation mode is that it saves energy and redistributes heat throughout the house, particularly helpful if you have a localized heat source like a woodstove. On the flip side, it can potentially transfer pollution from one room to another rather than expelling it altogether. While Smart Mode seeks a happy medium between the two, there are still times when recirculation mode should not be used at all—if someone is cooking, smoking, or during times of high occupancy. One way to override the Smart Mode during these situations is with a push-button timer, a common feature of HRV installations that temporarily ventilates the HRV during such events.

If you do use recirculation mode, here are some best practices to maintain good air quality:

–High quality filters (High Efficiency Particulate Filters, HEPA, in combination with activated carbon filters) should be added to supply duct to mitigates odor or pollution from spreading

— Constant recirculation should only be used when the building is unoccupied

–If recirculation is used during occupied periods, make sure the HRV is exchanging indoor and outdoor air for at least part of every hour

While recirculation offers the perk of saving energy, if you rely on it too much, you can undermine the benefit of having an HRV—to maintain indoor air quality that is healthy for both humans and structures.

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.

Glycol not always best for hydronic systems

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

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

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

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

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

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

Air Source Heat Pumps in Southeast Alaska

How an air source heat pump works. Photo credit: U.S. Department of Energy.

Air source heat pumps (ASHP) are a heating appliance that act like a refrigerator in reverse. Where a refrigerator removes heated air from its interior and transfers it to the room, an air source heat pump extracts heat from outside a house, and transfers it to a home’s interior. Using an ASHP in colder climates seems counterintuitive, but the truth is that “cold” outdoor air still contains heat, and an ASHP uses electricity to “step up” that heat to a temperature useful for space heating. Until recently, ASHPs have been used in areas that only experienced mild winters. However, ongoing advances in technology have resulted in ASHPs that can be installed in colder climates.

Southeast Alaska is a promising candidate for ASHP heating appliances, because it has a milder climate than the rest of the state and access to affordable hydroelectric power. Because ASHPs take some heat from the outdoor air and require less electricity than electric baseboards, they have the potential to reduce heating costs for homeowners who previously heated with electric appliances.

However, there is still uncertainty about the performance of ASHPs in cold climates, and about the barriers to their adoption in Alaska. CCHRC is planning to explore the opportunity of using ASHPs in Southeast Alaska in a new project: Southeast Alaska ASHP Technology Assessment. We will conduct a literature review, interview installers, distributers, and ASHP owners, create an inventory of existing ASHPs in Alaska, and model their economic and heating impact. If you are interested, look for the Technology Assessment on our website in early 2013!

Read CCHRC’s Ground Source Heat Pump assessment here.

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 are HRVs and how do they work?

Heat recovery ventilation (HRV) systems are becoming increasingly common in cold climate construction and are almost indispensible in today’s super-insulated, airtight homes. As older homes are receiving energy retrofits and becoming tighter and more insulated, they are facing the same indoor air quality issues you find in new construction. HRVs improve the indoor air quality of your home and save more energy than other types of ventilation. This article provides an overview of the basic purpose and advantages of HRVs.

The main job of the HRV is to supply fresh outdoor air to the house while expelling stale indoor air — which can contain things like moisture, animal dander and gases from combustion appliances and carpets. This is especially important in a home that is too tight to rely on passive air exchange.

At the heart of the HRV is a heat exchanger (often called a “core”) where exhaust air flows next to, but separate from, supply air. Here the cold incoming air is warmed by the heated outgoing air, recovering heat that would otherwise be lost. Most HRVs recover 70 to 90 percent of the heat, depending on the unit and controls, making it much more efficient in a cold climate than a simple exhaust fan that blows warm air directly outside. One of the newest and most advanced models is capable of recovering more than 90 percent of the heat from exhaust air.

The ducting of an HRV system typically supplies fresh air to bedrooms and living areas while exhausting humid air from bathrooms, kitchens, laundry rooms and crawlspaces. The HRV does not eliminate the need for a cooking fan, so a range hood still should be the main outlet for grease and smoke above the cook stove.

The HRV is designed to be balanced, meaning it takes in as much air as it exhausts, maintaining close to neutral pressure inside the home. It should not create a negative pressure in the home, like an unregulated exhaust fan might, which can cause appliances to back draft (suck in air from an exhaust flue and expose you to dangerous gases). It’s also important to remember that HRVs are not meant to supply air to combustion appliances.

Efficient residential units use about as much power as a 60-watt light bulb when running, and are getting more and more efficient. As with any appliance, an HRV requires some maintenance, such as checking the built-in filters every fall to see if they need to be cleaned or replaced.

In addition to providing reliable ventilation in a home, HRV systems can serve several other roles. You can install an in-line filter system on the warm-side supply air port that will filter particles and odors from the incoming air. For example, in the winter this can help keep particulate pollution (from wood-burning and other sources) out of your home.

With the right controls, an HRV can also work in recirculation mode, which distributes heat to hard-to-reach areas in the house (a big help for occupants using a woodstove). Although be aware that recirculation reduces overall fresh air exchange and can redistribute odors from unwanted areas in the house. If you own an older unit, a control upgrade may be a beneficial and cost-effective option.

While it may seem expensive up front, you should look at an HRV system as an investment in a healthy home and peace of mind. In this climate, indoor moisture can cause problems not just for the structure, potentially condensing in the walls and leading to mold and rot, but also for occupant health. An HRV will protect the occupants as well as the structure by removing excess moisture before it has a harmful effect.

If you’re thinking about purchasing a system, make sure you learn about the specifics and find an installer who is willing to educate you and stand behind their work.

What is reflective insulation and does it work in a cold climate?

Reflective insulation is typically made of aluminum foil on a backing like rigid foam (pictured here), plastic film, polyethylene bubbles or cardboard.

Reflective insulation is a type of thermal insulation with at least one reflective surface that is installed so that the surface faces an air gap. It is usually made of an aluminum foil installed on a variety of backings, such as rigid foam, plastic film, polyethylene bubbles or cardboard.

CCHRC recently researched the use of reflective insulation in cold climate construction, reviewing other studies and testing two foam insulations with reflective facers. Researchers found that the use of reflective insulation has very little to offer cold climate construction.

To understand how it works, you need to understand the three types of heat transfer: convection is heat transfer through air movement; conduction is heat transfer through solid materials that are touching; and thermal radiation is when heat travels in electromagnetic waves, like energy from the sun.

Reflective insulations are designed to reduce heat transfer through radiation by placing a surface that reflects thermal radiation in combination with an air gap. The reflective surface reflects most of the thermal radiation toward the air space, preventing it from being absorbed by the material. If you don’t have an air space, then the heat is lost by conduction through the reflective surface. In real life, all these forms of heat transfer occur simultaneously. (Unless you travel to space to remove the atmosphere (air) from the equation. This partially explains why NASA took an interest in reflective insulations, as they faced very different conditions than we do in Alaska.)

In warmer climates, it is common to add reflective insulation in the attic to reduce heat transfer from the roof decking to the underlying insulation, reducing overall solar heat gain within a building. But in cold climates, we have different concerns. For example, homes lose heat primarily from air leaking through the attic and walls and conduction through all components of the house. Because most heat loss occurs this way, reflective insulation would not make much difference in reducing the overall heat loss of your home.

To illustrate this point, let’s examine part of a house where a reflective insulation system is added. If you created a 1-inch air gap into the wall or ceiling with a reflective surface on one side, you could expect to gain around R-2. But walls and ceilings are typically insulated in the range of R-20 to R-60, and reflective insulation faces sharp diminishing returns if multiple layers are installed. Also remember that the air gap needs to prevent airflow and the reflective surface needs to stay clean from dust and moisture.

In addition, many reflective insulations can increase the potential for moisture problems in your home if not placed properly, as they often act as strong vapor retarders. So if you’re using these products, you need to consider not just how they affect heat loss, but also moisture flow.

Watch out for claims about reflective insulations providing benefits that go beyond R-value. All of the product’s insulation value is captured by the R-value, just like fiberglass batts, foam board, and other insulation products. If there are additional benefits, such as reducing air leakage, then those benefits can be measured and compared to other air barrier systems.

In essence, reflective insulation may help in warmer climates but is not a great fit for a cold place like Alaska.

UAF Sustainable Village Week 18: Interior finishing

It’s finishing time at the Sustainable Village! The devil is in the details, and we’re detailing ceilings, floors, corners, railings, trim, and everything else. The time lapse shows workers installing beautiful birch paneling on the upstairs ceiling as well as cabinets and appliances.

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.

Design

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.

Insulation

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.

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

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

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

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

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

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

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

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

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

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

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

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