While the thermal performance of a roof insulation is an important metric to consider when selecting and specifying products, several other material characteristics need to be evaluated, such as compressive strength, fire resistance, moisture absorption resistance, dimensional stability, and substrate durability. Roofing insulation manufacturers provide laboratory test results for these and other material characteristics. However, limited information is available for the performance of aged in situ materials. This lack of information can potentially lead to issues because the performance of aged, installed material may not match the performance at the time of its manufacturing, and more importantly may no longer meet the project specifications. The reliability of a product's long-term durability is critical to the performance of the complete assembly. This paper will discuss the need to compare actual in-service performance characteristics of aged material to the performance of new as-manufactured material. This type of information can help design professionals and owners make an informed decision about the material's suitability and longevity. To demonstrate this type of evaluation, this paper presents two case studies that reviewed and compared the aged in situ performance of stone wool insulation to new as-manufactured data. The case studies focused on multiple performance metrics tested per ASTM standard test methods. The stone wool insulation was installed in two different roofs and had been in place for 10 years at two separate sites in southern Canada. Multiple insulation specimens were extracted as representative samples for testing. The study reviewed the moisture content, compressive strength, adhesive/cohesive strength, and peel strength of the insulation. The results are compared to newly manufactured specimens to evaluate if or how the insulation's performance has changed over the 10 years.