Home Insulation

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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 21C.
• 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 m2 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/(m2K). At attic Temp of 45C.
• Calculate the interior convective coefficient
  based on free convection. h.1078 w/(m2K). At
  home temp of 21C.
• Build Thermal circuit
• Calculate the energy transfer based on insulation
  of R-30 and R-38 (both have units of m2K/w).
• Compare results

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Solution
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Results

• For R-30 insulation q71.93 w.
• For R-38 insulation q60.037 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.