Making Houses Work

If pilings are used on permafrost, they must be installed to a depth that will both support the structure and resist frost jacking due to seasonal ground movement.

Permafrost is loosely defined as soil and/or rock that remains frozen for more than two years. In the Fairbanks area, permafrost tends to be discontinuous and is concentrated primarily on north-sloping hills and in lower elevations with heavy ground cover. Big trees do not guarantee the absence of permafrost; it might just mean that permanently frozen ground or ice is down far enough that the soils in that spot can support a larger root system. The only way to be certain of what the ground contains is to have a soils test drilling done.

With permafrost, the safest bet is to it avoid it altogether and move to another piece of land. This is easier said than done, particularly because of the scarcity of buildable land near Fairbanks that is affordable. If you decide to build on permafrost, be as strategic as possible. Smaller and simpler structures will tend to fare better than larger, more complicated ones.

Minimal site disturbance is the accepted practice. The trees and the ground cover are your best friend. They protect and insulate the ground from the heat of the summer. A great example is the green moss you find on many of the shaded low-level areas in Fairbanks. Moss has a high insulating value, and in many cases if you dig down a couple of feet, the ground might still be frozen in the middle of summer.

Strategies for construction on permafrost include:

• As a general rule, the organic layer of ground cover provides insulation and should not be removed, as this will increase the risk of thawing any frozen ground underneath.

• Elevate and properly insulate the bottom of your house to prevent heat losses through the floor system from reaching the ground underneath, which can lead to thawing.

• In post and pad construction, use a thick gravel pad that is significantly wider than the house itself (also insulated if possible) to stabilize the ground and spread building loads.

• If wood or steel piles or helical piers are used, they must be installed to a depth that will both support the structure and resist frost jacking from seasonal ground movement.

• Cut trees sparingly to maximize site shading (while permitting for a fire break).

• Build a wrap-around porch, which will help shade the ground around and underneath the house.

• Incorporate large roof overhangs to shed water away from the house and provide shade.

• Install gutters and manage site drainage well away from the house.

• Retain an engineer familiar with local soils conditions to assist in designing a foundation system that will adequately and safely support your home on the soils specific to your site.

• Septic systems also must be engineered to function on permafrost, and remember that conventional systems might risk thawing the ground.

Other Resources 

Permafrost Technology Foundation case studies: http://www.cchrc.org/permafrost-technology-foundation-library

U.S. Permafrost Association website: www.uspermafrost.org/education/PEEP/ptf-manuals.shtml

UAF Cooperative Extension Service online publications at www.uaf.edu/ces.

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.

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.

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.

CCHRC is demonstrating an innovative foundation design at the Sustainable Village. Two of the homes, sitting on permafrost about 9 feet deep, will be built on steel piles, a common method for building on frozen ground. The other two, situated on stabler soil, will have an insulated mat foundation.

Builders laid the mat foundations last week. They include a geotextile mat placed directly on the soil with several feet of gravel on top. PVC pipes are embedded in the gravel in a grid formation as a backup cooling system. Resting on the pad is a steel floor assembly. Spray foam was applied against the entire system for a monolithic layer of insulation at least 10 inches thick. This is designed to prevent heat from inside from transferring to the ground. Temperature sensors were strung about 10 feet down into the soil to monitor any changes. If needed, cold air could be circulated through the piping system in the winter to lower the temperature, as insurance against shifting ground.

Here’s a look at the pad preparation.

Are you curious about what’s in your walls, but not quite ready to tear them apart to find out? We’ve dissected a standard wall system to see what’s inside, and what it tells us about your home energy performance and the durability of your envelope.

Whether you’re building a new home or retrofitting an existing one, this video will show you the key to tight, long-lasting walls. It will give you an understanding of the three main issues facing walls in a cold climate: air leakage, moisture movement, and conductive heat loss. CCHRC building educator Ilya Benesch will show you how these effects are at play in yours walls, how to spot them, and how to deal with them. Enjoy!

attic insulation stained with dirt

Although mold can’t be ruled out, it is quite probable that it may be caused by something else.

Just because you have dark spots on your insulation doesn’t mean you have a festering mold problem. Air leakage from inside the house through the walls and ceilings can produce some pretty dramatic localized black spots in fiberglass batts.  Typically, fiberglass batting isn’t good at stopping air leakage, but it does act as a very effective filter material for airborne dust particles. Dirty insulation is a phenomenon that is especially common in older, leaky houses in the Interior.

In a recent attic inspection of a 30-year-old home, CCHRC found batt insulation riddled with dark streaks. The source of the streaking was a lot of air leakage through electrical outlets, wiring penetrations, gaps in the vapor retarder, gaps around furnace ducting, chimney, and other sources.

Particulates released by combustion appliances, such as wood stoves, boilers, furnaces, diesel heaters or auto exhaust, can produce very fine soot that can build up over time in insulation. Tobacco smoke can also contribute.

Look for clues in the pattern of the dark stuff. Does it match up with an air leakage pathway? For example, air from inside the home can exit through an unsealed electrical penetration in the ceiling and follow the wiring through the insulation, depositing dirt in the surrounding fiberglass along the way.

Does the wood framing or sheathing around the insulation also have black spots? If not, it is more indicative of dirt than mold.

If you are still concerned that you may have a mold problem, call a mold expert to make a positive identification.

You might think you have R-40 walls, but have you factored in your studs and windows? With the recent emphasis on home retrofits and energy efficiency, many homeowners are defining their walls by R-value.

The whole wall R-value factors in the R-values of the insulated wall, stud, and window.

For instance, if you have 2×6 walls filled with fiberglass batt insulation (R-19), plus drywall and plywood, you probably consider your overall R-value to be R-21. But that only counts the insulated portion of the wall and ignores the weaker parts, such as windows, doors and structural framing (or studs), that provide primary paths for heat to escape. Just as water and electricity seek the path of least resistance, heat flows through the weakest thermal component of the wall assembly.

To see how much studs and windows affect the performance of your wall, CCHRC calculated the “whole wall R-value” for a hypothetical 2×6 house with 11 percent of the wall area taken up by studs (24-inch on center framing) and 15 percent taken up by double-pane windows.  The original R-21 wall is reduced to R-18.3 when you factor in the studs (R-8.8). And the whole wall R-value is further diminished to R-8.2 when you factor in windows with a U-value of 0.5 (standard double-pane windows).

How can this information help you improve the energy efficiency of your home? First, it gives an accurate picture of the overall thermal resistance of your wall. (Though there are many other components of a house that impact efficiency, such as the attic insulation, heating system, and ventilation system.) Second, it reveals the extent to which thermally weak points can counteract stronger points in your wall.

And third, it illuminates retrofitting options, each with their ups and downs. Replacing windows, for example, may achieve a greater whole wall R-value, but it can be pricey. Adding exterior foam, on the other hand, can be a cheaper way to cut heat loss through the insulated wall and the studs. But you must be careful to add the right amount of insulation, and possibly extra ventilation, to avoid moisture problems within the walls.

The best way to weigh these costs and benefits and make the most of your retrofit is first get a home energy audit.

Cold roof on the CCHRC building.

In severe cold climates, roofs face two important challenges; retaining heat effectively, and controlling moisture trying to escape from the living space.  The colder the weather and the longer the winter, the more pronounced the issues can become.  Deficiencies and poor building practices that are overlooked in a more forgiving climate become very apparent here in Fairbanks.   A basic understanding of your roof system and the challenges it faces can help to identify the sources of problems.

Roofs fall into two categories: “cold” and “hot.”  They can suffer from the same ailments.

A properly constructed “cold” roof maintains a continuous air space between the underside of the roof and the insulation. This air space is designed to do two things.  To some degree, it allows an exit path, through vents, for moist air that has leaked from holes in the ceiling vapor barrier into the insulation cavity. The space also creates a thermal break that helps prevent escaping interior heat from conducting directly to the roof’s underside, where it can cause the snow above to melt.

A “hot” or unvented roof relies on high levels of insulation to slow down heat transfer to the exterior.  The other critical component in a hot roof system is a near-perfect vapor barrier that keeps moisture-laden air from entering the roof cavity, where it can become trapped.

If either type of roof fails to retain heat, one result is ice damming, a fairly common sight in Fairbanks in mid-winter. The classic symptoms are large icicles hanging off of eaves and exposed spots on the roof where snow has melted away. Roof problems are more pronounced in our climate because we have an increased “stack effect.” Rising warm inside air will try to exit the building through leaks at the ceiling level. To replace it, dense, cold, outside air is drawn through cracks in the bottom of the house like a chimney. The greater the temperature difference between inside and outside, the stronger the stack effect, amplifying the heat loss.

Water vapor abides by similar laws. During winter there is a huge imbalance between moist, heated indoor air and extremely dry, cold outdoor air. Because water vapor molecules by nature try to reach equilibrium, they will move through any vulnerable areas (including solid wood) to balance the moisture levels. This is called vapor drive. The greater the temperature difference, the more intense the vapor drive. When a house has high indoor humidity, the combination of stack effect and vapor drive can cause severe moisture problems inside the roof if it is poorly sealed.   Gone unnoticed, this can lead to structural damage as well as mold and its accompanying health issues.

Whether your roof is hot or cold, three elements will keep problems at bay: good indoor moisture control, adequate insulation, and good sealing.

Our new report shows that ground source heat pumps are an effective and affordable technology for parts of Alaska, including Fairbanks, Juneau and Seward.
In this video, CCHRC researcher Colin Craven discusses how heat pumps work and what you have to think about before installing one in Alaska.