8. Efficiency and Conservation
Students will be able to:
- Describe some of the materials used to insulate modern homes and buildings.
- Collect data on the ability of different insulation types to retain heat, and calculate their heat loss.
- Assess the efficiency of different insulating materials.
- Assess a structure's resource use, and propose ways to make the structure more efficient.
Context for Use
This module is for use in an undergraduate laboratory class with twenty to thirty students enrolled. It was developed for undergraduate non-science majors enrolled in a general education science course at a four-year teaching college. The module, however, may be used for science majors. The module can be completed in 1.5 to 2.0 hours
This module was developed as part of a larger course and is the eighth module in the course. Nonetheless, it can be used independently in a different course (e.g., an environmental science lab). However, if you choose to teach the module independently, students would still benefit from reviewing material in the first module: Electricity, Work, and Power.
Description and Teaching Materials
Student materials for this module are provided at the following link:
Assign a group of two or three students to a test box. Have one student read the thermometer in the flask while the others record data. Record the data for the time period (every three minutes over a half hour).
The materials needed are listed below. Ideally, you will be able to replicate each treatment three times. For this experiment, you will need:
- Three boxes constructed of cardboard and another three boxes constructed of foam core (or any insulating material). The box should be about 30 x 30 x 25 cm, or large enough to hold a 250 ml Erlenmeyer flask.
- Nine 250 ml Erlenmeyer flasks filled with hot water (three for each cardboard box, three for each foam core box, and three to serve as the "no insulation" treatment).
- Thermometers to measure water temperature changes in each flask.
- A graduated cylinder to measure out 200 ml of water into the flasks.
Structuring Class Time
Quiz & Discussion. This module is the eighth in the course and follows the module on Better Ways to Illuminate. It can be taught as a stand-alone module, but you may still want to have the students review the material in the first module on Electricity, Work and Power. Begin the class with a quiz from the prior week's module. Have students come to class with quiz questions, and select five students to read their questions aloud. After each student recites her/his question, pause for the appropriate time for their classmates to write answers. If you get questions at the lower end of Bloom's Taxonomy, e.g., on facts or definitions, you will want to encourage higher-level questions. For example, there may be a question like "what is the percent of energy spent to heat a home?" You can have the students answer that question, but also get them to move beyond it. For example, push the students think about how and why that number varies among the homes. After all five questions have been completed, ask five different students how they answered the questions. This format allows focused discussion on the topic. Students have an opportunity to work through their understanding of the material. Also, the teacher gets feedback on the effectiveness of teaching materials and teacher delivery—what is clear and what is still muddy. Use the instructor-regulated discussion pedagogy as explained in the course overview for developing discussions of the current module.
It is important to help the students use what they learned in the earlier modules to gain a deeper understanding of this module. As the professor, you can help them apply what they have learned from previous modules, especially from the first module and the module on Passive Designs. This module takes some of those concepts and applies them to energy efficiency in the home by examining the effects of insulation on heat loss. The opening quiz reinforces the scaffolding of learning and forces students to revisit the previous module twice, once during their studies when they review for the quiz and formulate the quiz questions, and again when they participate in class discussions.
The flipped-classroom structure advocated for this course facilitates the development of metacognition by the students, directly involving them in the learning process. The use of student-generated questions for quiz and discussion helps students become aware of how they learn and understand the material. This is a big departure from the simple memorizing of terms and concepts that characterized much of their earlier education. Having students think of questions for quizzes and discussion will inform their approach to learning in general. Another strategy used in the course is requiring the students to apply basic science concepts to understand a technology, and then to requiring them to think about the application of that technology in the real world. In this particular module, the students can research their own home's energy use and think of ways to reduce its energy consumption.
A major theme of this course is that students see the various technologies in the context of the global system. This module on Energy Efficiency and Conservation provides an opportunity for students to see the effects of insulating materials on heat loss or the amount of energy consumed in a home. This consumption, in turn, can have an effect on overall fossil fuel emissions. The students can think this through and—depending upon the mix of energy generation for their area—calculate what the reduction in carbon dioxide emissions would be if homes in their city achieved a 10% or 20% reduction in energy consumption.
Student Presentation. Each class should have one or two PowerPoint presentations by students, given either during the current module or at the beginning of the next module. This activity involves peer instruction.
- Present a case study of an existing building that was successfully modified to increase its efficiency. Present before and after comparisons.
- Assume that the university hired you to improve the efficiency of the building in which this class is being held. Explain the things that you would do to achieve this goal.
Hands-on laboratory work. In this module, students track temperature changes in flasks of water surrounded by different insulation materials and calculate the heat loss.
Please see the course overview to see how we suggest that you structure the class.
Teaching Notes and Tips
The lab, as described, compares heat loss associated with cardboard versus foam core versus no insulation. However, depending upon access to materials, one can create a variety of insulation types for comparison. One could also double up on the foam insulation to increase the R values.
It is important that the flasks begin at the same temperature, which can be done by heating them in a microwave oven for the same amount of time. We used 250 ml flasks, but any sized flask can be used.
- Graph the results for the cardboard vs. foam boxes, with time on the X-axis and temperature on the Y-axis. Discuss your findings.
- Determine the average number of calories of heat lost from each bottle in the experiment using the average initial and final temperatures for each treatment. Discuss your findings.
- Rank the effectiveness of the boxes from the best insulated to the poorest insulated. Using these same materials, how could you make them even more insulated?
- Compare your home energy use to similar homes. Gather the following information: (a) number of people living in your house (b) square footage of your home (c) the different fuel types used in your home (e.g., fuel oil, propane, natural gas) and d) the your utility bills from the last twelve months. Go to:
What was your yardstick score?
What are some things you could do to reduce energy use in your home?
Student assessment is based upon three different student activities: student-generated quizzes and discussion, student presentations, and module reports based upon laboratory and other work. In addition, there is a pre/post test that can be used to provide further assessment. The assessment methods for this module can be found on the course assessment page.
References and Resources
Al-Houmoud, Mohammad (2005) Performance characteristics and practical applications of common building thermal insulation materials. Building and Environment 40:353-366.
Department of Energy's Insulation Fact Sheet
Gardner, G. T., & Stern, P. C. (2008). "The short list: The most effective actions US households can take to curb climate change." Environment: Science and Policy for Sustainable Development, 50(5), 12-25.
- Home Insulating & Insulation Techniques and Products from Green Building Energy Savings
- Types of Insulation from Energy.gov
- 2009 Residential Energy Consumption Survey from the US Energy Information Administration
- Home Energy Yardstick from Energy Star