Abstract

Objective

The objective of this project is to see which of a variety of materials that are commonly used in home construction acts as the better insulator against heat.

Introduction

When the weather turns colder in the wintertime, you put on an extra layer (or two!) of clothes before you go outside to keep warm. The extra clothing helps to conserve your body heat so that you don't get cold. It acts as an insulating layer around you, resisting the flow of heat to the cooler outside air.

Buildings need insulation, too, to resist heat flow out of the building during cold winter months, and to resist heat flow into the building during hot summer months.

"Heating and cooling ("space conditioning") account for 50 to 70% of the energy used in the average American home. About 20% goes for heating water. On the other hand, lighting and appliances and everything else account for only 10 to 30% of the energy used in most residences" (DOE, 2002a). You know you can save electricity by turning off lights, televisions, computers, and other appliances when they are not being used, but what if you could do something about the bigger part of home energy use—heating and cooling? What is the best insulation material to make the heat stay inside the house in the winter time?

Insulation materials are characterized by their resistance to heat flow, commonly referred to as the "R-value" for the material. In this experiment you'll make an insulation sandwich between two boards, and measure the temperature difference between the two boards as you heat one side with a hair dryer. Which insulation material will work best to resist the flow of heat from one board to the other?

Terms, Concepts, and Questions to Start Background Research

To do this project, you should do research that enables you to understand the following terms and concepts:

• thermal insulation,
• building insulation,
• different methods of heat transfer,
  • radiative,
  • conductive, and
  • convective;
• thermal resistance, or R-value.

Questions

• What does "R-value" measure?
• Can you explain the differences between radiative, conductive, and convective heat transfer?

Bibliography

• DOE, 2002a. "Insulation Fact Sheet," Department of Energy [accessed October 25, 2006] http://www.ornl.gov/sci/roofs+walls/insulation/ins_01.html.
• DOE, 2002b. "Types of Insulation: Basic Forms," Department of Energy [accessed October 25, 2006] http://www.ornl.gov/sci/roofs+walls/insulation/ins_tab1.html.
• Wikipedia contributors, 2006. "Thermal Insulation," Wikipedia, The Free Encyclopedia [accessed October 25, 2006] http://en.wikipedia.org/w/index.php?title=Thermal_insulation.

Materials and Equipment

To do this experiment you will need the following materials and equipment:

• two pieces of 1/2-inch plywood, about 12" × 12",
• 12" × 12" samples of various insulation materials for testing, e.g.:
  • fiberglass,
  • rock wool,
  • cellulose,
  • polyurethane foam,
  • extruded polystyrene foam (XPS),
  • expanded polystyrene foam (EPS or beadboard),
  • polyisocyanurate foam,
  • vermiculite,
  • etc.;
• two C-clamps,
• hair dryer,
• thermometer,
• helper.

Experimental Procedure

1. Do your background research so that you are knowledgeable about the terms, concepts, and questions, above.
2. Decide which types of insulation material you want to test, and purchase samples. Try to find at least four different materials to test. Which material do you think will perform best at resisting the flow of heat?
3. To test the different insulation materials, you will sandwich each material between the two pieces of plywood, using the clamps to hold the insulation in place.
   1. Test one material at a time.
   2. Use just enough pressure to hold the insulation in place without compressing it.
   3. For a fair comparison of the materials, use the same thickness of each material when testing. Stack up thinner materials to the same thickness as your thickest material. (What happens to the effective R-value when you stack up multiple layers of an insulating material?)
4. Measure the ambient temperature, and the temperature of each of the plywood pieces, and record the results in your lab notebook.
5. Heat one of the plywood pieces with the hair dryer for 15–20 minutes. Keep the hair dryer moving slowly in the same pattern across the board, and keep it at the same distance from the board.
6. At regular time points (e.g., every 2–3 minutes), measure the temperature of the heated piece of plywood and the temperature of the second piece of plywood. Take the measurement at the same place each time, in the center of the board. Record the results in your lab notebook.
7. Unclamp the plywood, remove the insulation, and allow the boards to cool back to ambient temperature. Then repeat the measurements with the next insulation material.
8. As a control, use an air gap (no insulation) between the boards as one of your conditions. Use two wood blocks that are the same thickness as your test insulation materials to hold the plywood boards the right distance apart. It would be best if the wood grain of the blocks is oriented parallel to the surface of the plywood boards, to minimize heat conduction through the blocks.
9. For each insulation material, make graphs showing how the temperatures of the heated board and the unheated board changed over time. The insulating material that performs best will show the greatest temperature difference. Did the results match your expectations? Why or why not?
10. Calculate the temperature difference between the heated and unheated boards for each insulation material. Make a graph of this temperature difference (y-axis) vs. the effective R-value of each insulation material. (Remember to adjust the R-value if you stack multiple layers!) What relationship do you find between temperature difference and effective R-value?
11. Which insulating material had the best price/performance ratio?

Variations

• The Department of Energy's Insulation Fact points out that how installation is installed can greatly effect how well it performs. For example, "insulation that is compressed will not give you its full rated R-value." (DOE, 2002a). Use the C-clamps to compress insulation between the plywood boards. How is heat transfer affected when the insulation is compressed? Do you get the same results for all types of insulation? Why or why not?

• For more science project ideas in this area of science, see Materials Science Project Ideas.

Credits

Andrew Olson, Ph.D., Science Buddies

Sources

• Phillips, D.A., 2003. "Which Is the Better Insulation Material?" California State Science Fair Abstract [accessed October 25, 2006] http://www.usc.edu/CSSF/History/2003/Projects/J1528.pdf.

Last edit date: 2006-11-03 11:00:00