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Teachers' Guide: Warm-up

Synopsis: This excercise introduces students to the Home Energy Saver simulation tool and familiarizes them with its use.

Pre-class work: Download the printable user guide and have students work with their parents to gather the inputs described on page 2 the night before the exercise. Question 1 should be skipped.

• Step 1: Students can divide into teams or work individually, depending on how many computers are available and teacher preferences.
   
• Steps 2: Students go to the Home Energy Saver home page, enter their Zip Code, and click on the button labeled "Go".
  
  
• Steps 3: At the resulting page, students should enter the information they collected on page 2 of the hardcopy user guide (question 1 should be skipped). When the information has been entered, the students should click on the "Start Calculation..." button, shown at the top of the form. At the resulting page, students record the annual cost associated with their existing house. This is given by the upper bar in the chart at the top of the results page.
  
  
• Step 4: Students report out their results to the teacher who indicates each result on a scatter chart, with the x-axis being conditioned floor area and the y-axis being the annual energy cost.
  
  
• Step 5: Teacher leads a discussion of the meaning of the results.
  
  
• Step 6: Teacher walks students through the next (deeper) level of user inputs (e.g. walls, windows, appliances) and the results page showing ranked retrofit recommendations. These input forms are shown (with some annotation) on the user-input guide, which the students can study at home and gather more information to refine the analysis they have begun in this session.
  

Topics for Discussion

• Do the data show a trend towards larger energy costs for larger houses?
• If so, what y-intercept is implied if the trend is projected to the point where x=0?
  • [Answer: space-heating and -cooling energy use tends to increase with house size]
• What is the meaning of this intercept?
  • [Answer: it is an approximation of the non-space-conditioning portion of household energy use]
• Why don't the results fall on a perfect line?
  • [Answer: there are many possible reasons, including differences in energy prices, differences in appliance holdings, window areas, number of people in house (effects hot water use), etc.]

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