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In full-scale attic tests at Oak Ridge national Laboratory, the R-value of 6 inches of cubed loose-fill attic insulation progressively fell as the attic air temperature dropped. At -18 F, the R-value measured only R-9. The problem seems to occur with any low-density, loose-fill fibrous insulation.(J.D. Ned Nisson, "Attic Insulation Problems in Cold Climates," Energy Design Update, March 1992, 42-43)
Convection Losses In Loose-Fill Insulation
Most people know that air penetrates the walls of a house. In fact, when the wind blows across some homes, its tenants can feel it. But what most people, including many engineers, do not realize is that there are very serious convection currents that occur within fiber insulations. These convection currents rotate vast amounts of air, but they are not fast enough to feel or even measure, with any but the most sensitive instruments. Nevertheless, the air constantly carries heat from the underside of the fiber pile to the top side, letting it escape. If we seal off the air movement, we generally seal in water vapor. That additional water often condenses and can become a moisture-source that rots the structure. The water, as a vapor or condensation, seriously decreases an insulation value — the R-value. The only way to deal with a fiber insulation is to ventilate. But ventilating means moving air that also decreases the R-value.
Cellulose insulation is made primarily from recycled newsprint that contains printers inks which can possibly outgas formaldehyde into a home. If there is any out gassing from inks, it should fall well below levels irritating most persons. However, an environmentally-sensitive person should be careful in selecting cellulose and install a vapor retarder between the insulation and the living space. (Note that the vapor retarder can exacerbate mildew problems if humidity levels in the house are high.) The newspaper is ground into a fine, fluffy powder, and it is then treated with a variety of chemicals (sodium borate, boric acid, or ammonium sulfate) to render it fire resistant and to discourage vermin from nesting in it. The inks used in printing newspapers are fairly toxic, and while there are some individuals who cannot tolerate the odor of a fresh newspaper, actually inhaling insulation containing this ink can result in a much more severe exposure. (Sourcebook for Sustainable Living, CSI number Div 7 Thermal and Moisture Problems, 07200 Insulation)
David Buscher, M.D., of Kirkland, Washington, presented several cases studies to a 1982 medical conference describing the negative health effects suffered by some of his patients after their homes were insulated with cellulose. Buscher found high levels of boron compounds in their systems. These are generally in the form of borax and boric acid, chemicals that should not be taken internally.
These chemicals apparently retain their ability to retard fires in the hot temperatures found in many attics. However, there have been instances when cellulose has indirectly caused a fire. This usually happens when either type insulation is installed in direct contact with an older style recessed lighting fixture. The insulation traps the heat created by the light bulb. This, in turn, causes the lighting fixture to overheat. Some modern recessed fixtures have thermostats within the fixture that turn the light off if it begins to overheat.
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