Tag Archives: cold climate

Sustainable Village: Laying Foundations

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.

How to build and maintain efficient, healthy walls

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!

What is causing all the black spots in my attic insulation?

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.


Why look at the Whole Wall R-Value of your wall?

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.


Hot roofs, cold roofs, and common roof problems

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.

How to heat your home using the cold ground

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.

Reflective Insulation-not a big help in cold climate construction

adding an aluminum facer to a 1-inch piece of EPS (expanded polystyrene)

CCHRC has just released a report on the effectiveness of reflective insulation in a cold climate. The insulation, which has a reflective surface, is commonly used in hot climates to reflect heat from the sun away from a building. For example, a home in Florida could add it to the roof decking to divert heat from the attic insulation and save on air conditioning.

But our researchers found that the insulation is less effective in a cold climate because it doesn’t add much r-value to an already well-insulated building.

Check out the full report here