EXPERIMENT 2:

HOW DOES WEATHERSTRIPPING WORK?

THINGS YOU NEED: All of the materials from Experiment 1. A sharp, small-bladed knife or a single-edged razor blade. Some heavy paper tape (the kind used to seal packages).

Weatherstripping around windows and doors, and caulking in cracks and crevices, both do the same job: they stop the “leakage” of cold air into your home during the winter. In technical terms, this leakage is called infiltration. . . and it isn’t all bad: some infiltration is desirable because it brings fresh air into your home. But, too much infiltration can rob your home of heat, and waste energy.

For this experiment, we’ll use the cardboard box from Experiment 1, but without the insulating cotton balls.

As before, fill the glass with water at room temperature, and place it in the box. Now, put some tape over the top of the box... leave a small opening large enough for the thermometer. Finally, place the thermometer in the glass, and put the box into your refrigerator.

The temperature will drop a bit faster than before (although not as fast as you may think!) because the insulation now consists only of the cardboard box walls and the air trapped inside the box. Make a note of how long it takes for the temperature to decrease by 5^OF. Check the temperature every three minutes.

Now, let’s add some infiltration. Peel off the tape carefully, and remove the glass. Then, cut a long “slot” (about l/8-inch wide) in each side of the box. The sketch on this page shows< you where to cut.

OK, let’s see what effect infiltration has. Perform exactly the same experiment as you did above: tape a glassful of room-temperature water into the box, and put the box into your refrigerator. You will find that the water temperature drops considerably faster.

Does this experiment cause you to wonder if your home has “too much” infiltration? Later in this chapter, we’ll build a “draftometer” to help you find out. As a rule of thumb, any crack or opening or crevice that you can see provides “too much” infiltration, and should be weatherstripped or caulked. On the other hand, infiltration through microscopic pores in the building material, around nail holes, through lock keyholes, etc., is considered to be “normal.”