Keeping your cool

Fresh food must be kept at a refrigerated temperature of 40 degrees F to stay edible for a week, whereas a freezer needs to be able to retain a constant 0 degrees F. The successful operation of any refrigerator is almost entirely dependent on the efficiency of the insulation surrounding the icebox. Insulation that is too thin or of the wrong material can double its operating time and hence its power consumption.

If you are planning a new installation and calculating the physical dimensions of the box, you must allow for the thickness of insulation required to construct a thermally efficient unit. If you already have an unrefrigerated icebox that you plan to convert, check the thickness and type of insulation first, as it will almost always require upgrading. The minimum insulation thicknesses recommended for the Northern Hemisphere are: (fridge/freezer) 2in/3in (sides), 3in/4in (bottom) and 1in/2in (lid). For tropical climates, add another 1-2in all round.