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What Happens When a Blanket of Insulation Conceals Overloaded Wiring?
In a recent two-week period, the Syracuse, NY, Fire Department had five fires involving blown-in cellulose insulation. It surely is a case where homeowners trying to save money ended up spending more in the long run. What's going on?
Cellulose is "green." This insulation is 80% post-consumer recycled newsprint. Most often, it is chemically treated with non-toxic borate compounds to resist fire, insects, rodents and mold. For those whose homes were built in the 1950s and who are looking to increase the R-value of their homes' insulation blanket, it appeared that adding blown-in cellulose is just the ticket. (According to the U.S. Department of Energy/Oak Ridge National Laboratory, "Insulation is rated in terms of thermal resistance, called R-value, which indicates the resistance to heat flow. The higher the R-value, the greater the insulating effectiveness. The R-value of thermal insulation depends on the type of material, its thickness, and its density." See http:// www.ornl.gov/sci/roofs+walls/insulation/ins_02.html.)
So why all the fuss? In total, we have had seven incidents involving blown-in cellulose insulation within two months. In defense of the product, I will admit that it was not the cause of the problem, but it definitely was a contributing factor. In all cases, the homes were at least 50 years old. The original insulation was fiberglass batting with paper backing. The wiring at each structure was the original cloth-covered non-metallic two-strand copper. And at each incident, blown-in cellulose insulation completely blanketed the attic space. This insulation was added many years after the home was constructed to help increase the insulation blanket.
Another common factor at the fires was the existence of the original 60-amp fuse box in the basement. With these old services, it was possible to circumvent the protection by screwing in a larger-amp fuse. Back then, the fuses (known as Edison base) were interchangeable. The newer safety fuses have different threads for each amperage. Higher amp fuses cannot be screwed into a lower amp circuit.
Recipe for Disaster
Overloading of electrical circuits is the human element of the equation. Summer comes and occupants install a window air conditioner. Perhaps it's cold and they use an electric blanket. In the next room, junior has his computer...