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Home Insulation By: Jeff Krise

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Introduction Analyze the rate of heat transfer from the attic to the interior of the home. Based on summer average temperatures in the attic with the home maintained at 21°C. This is to compare insulation thicknesses and possible monetary savings based on the energy transfer rate reduction by using better insulation. Home has an area of 121 m^2 with a length of 9.14 m and with of 13.24 m.

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Heat transfer problem Find the exterior convection coefficient based on low velocity air (2m/s) moving in attic. h=.98 w/(m^2*K). At attic Temp of 45°C. Calculate the interior convective coefficient based on free convection. h=.1078 w/(m^2*K). At home temp of 21°C. Build Thermal circuit Calculate the energy transfer based on insulation of R-30 and R-38 (both have units of m^2*K/w). Compare results

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Solution

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Results For R-30 insulation q=71.93 w. For R-38 insulation q=60.037 w. Total energy savings is 11.89 watts. Based on 24 hr per day of these temperatures. Over the period of one month this is approximately 8.56 Kilowatt-hours. At current energy cost of 12 cents per kilowatt-hour this equates to a savings of 1.03 dollars per month.

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Conclusion I would not recommend spending the amount of money it would take to add the extra 4 inches of insulation to the entire attic surface area to gain this small amount of energy savings per month.

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