Tag Archives: combustion

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.


How long does firewood take to dry in the Interior?

various storage scenarios tested at CCHRC

Wood-burning practices have come under scrutiny in recent years as the Fairbanks area has been cited for poor air quality by federal regulators. Increased wood-burning, a low-cost alternative to heating oil, has led to elevated levels of PM 2.5, a range of particulates linked to respiratory problems.

In an effort to lower emissions, the borough set fines for burning wet wood. But that’s not the only reason to burn dry wood–it also produces more BTUs.

How long does it take to fully cure firewood (a moisture content of 20 percent or less) in this climate? It depends on the species of wood, when you harvest it, whether you split it and how you store it.  A study at CCHRC shows that wood can dry rapidly over the summer—no matter when it’s harvested—but not over the shoulder seasons or winter. That means firewood harvested in the fall won’t be fully cured by that winter.

Split wood harvested in the spring took anywhere from six weeks to three months to dry over the summer, depending on the storage method. 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 approximately three months to cure.

Unsplit wood, on the other hand, didn’t cure completely over the summer in any storage scenario. Though it had dried significantly 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 actually got wetter under a tarp over the winter.

Several other factors should be considered when seasoning your wood. Spruce and birch tend to dry more quickly than aspen. And your drying times will also 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 over a single summer—so you can stay cozy and burn cleanly over the winter.