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Attic Ventilation
Tests continue to show that attic ventilators have little effect on home cooling costs or indoor comfort if the home has adequate attic insulation. Studies conducted by the National Bureau of Standards and Progress Energy uniformly support this conclusion. Some surprising facts were revealed by Progress Energy research conducted over two consecutive summers in Florida. The studies involved 30 different homes and outdoor temperatures ranging between 88 and 95 degrees Fahrenheit. During the tests, attic temperatures generally did not reach excessive levels. The highest recorded temperature at the peak of a roof was 134 degrees Fahrenheit and the average temperature was 127 degrees Fahrenheit. Temperature immediately above ceiling insulation reached 119 degrees Fahrenheit, and averaged only 103 degrees Fahrenheit.
With a turbine ventilator operating, attic temperatures fluctuate – sometimes decreasing about six degrees and, surprisingly, sometimes rising by six degrees. These relatively small changes in temperature had little effect on air conditioning energy use since attic insulation retarded heat flow from the attic into the home.
Most homes already have some type of attic ventilation such as screened eaves or gable vents since it is required by the state building code. Such ventilation prevents moisture build-up and minimizes the possibility of wood decay. Progress Energy research also indicated that additional ventilation is unnecessary and would not significantly affect cooling costs if the home is adequately insulated.
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