The IIAR Guideline for Installing Insulation on Ammonia Refrigeration Systems was developed to enhance the safety, reliability, effectiveness, and longevity of insulated piping, vessels, and other equipment. It provides detailed instructions for installing insulation systems, provides examples of poorly installed or maintained insulation systems, and provides quality assurance guidance to help owners and contractors achieve a high level of quality for installed insulation systems. This guideline focuses on the appropriate steps in installing insulation systems for cold piping and equipment on new and existing ammonia refrigeration systems. Additional precautions for working on or around charged ammonia refrigeration systems are necessary but are not addressed within the scope of this guideline. This guideline was developed as the result of an Ammonia Refrigeration Foundation research project. Its scope is limited to the application of polyisocyanurate (PIR) and extruded polystyrene (XPS) because most refrigeration applications use these two types of insulation.