I compared the insulation value of sawdust and leaves. Both are inexpensive and easy to obtain, especially leaves during autumn. The setup is shown in Figure 1. I used old yogurt cups, 750g size, and small styrofoam cups placed inside, with sawdust and leaves as insulation in between.
I included a control in the experiment. This is a yogurt and styrofoam cup with no insulation in between (farthest right in the picture).
Inside the cups I placed two ice cubes wrapped in aluminum foil (Figure 2 and 3). The foil acts as extra insulation. It reduces heat gain/loss due to radiation.
I sealed the containers (Figure 4, 5, 6) and set the timer.
While I was waiting I set up another experiment to see how much insulation value aluminum foil has. I wrapped an ice cube in aluminum foil and compared the rate of melting to a bare ice cube (Figure 7).
The ice cube with aluminum foil wrapped around it melted about half as fast as the one without foil.
Here are the results of the above tests:
The melting time of the ice cubes, with leaves and sawdust as insulation, are about the same - 5.5 hours. The melting time for the control is significantly less. I don't have its exact time of melting as I missed the window (I didn't check frequently enough).
I would have to conduct more tests to gain a sense of which is truly the better insulator, the leaves or sawdust. But regardless, due to their abundance and low weight, leaves are the best practical choice for use in my next test: Comparing insulation value with a commercial cooler.
First, I weighed three equal bags of ice, each weighing 1370g (Figure 8).
Next, I put one bag of ice inside a garbage bag full of leaves, and the other bag inside a cooler (Figure 9, 10). The third bag I left as-is (Figure 11), with no insulation surrounding it (control). I set up the test in the garage.
The average ambient temperature was around 8-10 degrees Celsius for the duration of the test. Obviously, the ice melted slower than it would in the summer, but I'm mostly interested in relative performance anyway.
The results are as follows:
• The ice without insulation completely melted after 35.5 hours
• The ice in the cooler completely melted after 52 hours
• The ice insulated with leaves completely melted after 135 hours
The trapped air between the leaves is what makes them such a good insulator. You can pack a lot of them into a big space to get a high degree of thermal resistance. The result is excellent insulation, even better than some commercial coolers (and of course, cheaper).