In 2009, President Obama proposed an initiative to decrease our country's energy consumption and dependence on fossil fuels. One key to this plan was to decrease the amount of energy used to heat and cool our homes through government incentives. The EPA estimates that the average American household spends over $1000 annually for heating and cooling.1 One of the most cost-effective ways of decreasing energy use in your home is to stop air penetration and increase the amount of insulation by installing insulated doors, insulated windows, and cavity wall insulation. But not all options are equally effective, nor do they have equal costs. So how can consumers determine which option improves their homes' insulation the most? In this paper, I present an analogy to simple resistor circuits that can be used by introductory students to answer this question.

2.
Joseph F.
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8.
9.
ENERGY-STAR rated doors must have a U-value less than 0.21 BTU/(h·ft2·°F)
according to http://www.energystar.gov/ia/partners/prod_development/archives/downloads/windows_DoorsSkylightsProgRequirements7Apr09.pdf. From the units it is obvious that the U-value is the inverse of the R-value. I calculated the stated value of the ENERGY STAR door using the same surface area and exterior wall values used in the vestibule.
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