RE: To Insulate or Not to Insulate
I don’t have one preference on the amount and type of insulation for boat refrigeration what I do have are several recommendations. Production boats less than ten years old that are not used as a live aboard or that keep the refrigeration running full time, should not need additional insulation. The need for available energy on these boats is more of a problem than the amount of insulation. Most boats have expanded polyurethane foam around the ice box/refrigerator liner. There are generally open air spaces between the insulation and other structures that can be filled with additional insulation either spray foam or extruded foam. All insulation will degrade over time by drying out and releasing the insulating gases. This causes the cells to absorb moisture. The air spaces beyond the insulation do help to dry out older insulation when a boat only has part time refrigeration. For a boat that has recently been used as a live aboard, adding insulation over moist insulation is a mistake. The two points to consider when selecting insulation are its R value, and its ability to reject moisture. Extruded foams are better than expanded foams because their density is controlled. Extruded polystyrene foams are more moisture resistant than extruded polyurethane foams although polyurethane has a 30% higher R value than polystyrene. I have always recommended polyurethane extruded insulation wrapped and sealed in plastic when building a refrigerator box. If you want to add more insulation to the outside of the box use urethane insulation, if the insulation is to be added to the inside, use extruded polystyrene like DOW’s Blue Board. For more information on insulation, click on Insulation, on my web page.
