Q: I want to add insulation to my refrigerator box. What are the latest and best products to consider? I am aware of Glacier Bay panels but they are quite expensive.
Mike Dunn, Annapolis, Maryland

A: Glacier Bay is the best-known builder of superinsulation. These are vacuum insulation panels and they are in a class by themselves in terms of insulating capacity per inch of thickness, having R-values ranging from over 20 to around 70 per inch. While expensive, they carry a 25-year warranty. Cheaper panels (with shorter warranties) are more fragile and should be avoided. The next best insulating materials are urethane and foil covered polyisocyanurate boards at around R-6. Conventional Styrofoam "blue board," the common house insulation, rates slightly lower at almost R-5 per inch. Traditional two-part, open-pour urethane foam is in the same general R-5 region but it’s more difficult to get consistent results with cut and fitted boards due to hidden bubbles and voids. A combination of board material assembled with gap filling foam works well. The only reason anyone would require the superinsulation is if there is just not enough room for more conventional insulation. If you have room for 6" of conventional insulation it will perform nearly as well as a superinsulting panel. Insulation is only one part of a well-made icebox. Construction quality, especially the details of how the insulation is fitted around the icebox to avoid gaps and “thermal shorts” and a well-sealed gasketed top are equally important. [For complete details on rebuilding an icebox refer to DIY 1999-#4 issue.]
-- Nick Bailey