New building code initiatives and legislation in the United States are ushering in requirements for increased climate awareness and energy efficiency. Although some have been rescinded, such as the 2022 Inflation Reduction Act, updates to ASHRAE 90.1, Buy Clean initiatives, LEED v5, and increased adoption of the 2021 International Energy Conservation Code continue to move forward. Common themes within these initiatives are employing clean energy, lowering embodied carbon, and improving energy efficiency. One way to increase energy efficiency is to increase thermal insulation within the building envelope. This paper reviews emerging trends in codes and legislation and their implications for thermal insulation, with a focus on two areas. First, the importance of considering insulation’s impact on a building’s operational phase carbon use alongside its embodied carbon footprint when evaluating its whole-life carbon impact. Focusing on an operational energy analysis using the Department of Energy Standalone Retail Prototype Building, incrementally adding polyisocyanurate roof insulation above the deck to determine the overall building energy usage and CO₂ emission equivalents. Results from this study show that increased roof insulation provides whole-building energy and carbon dioxide emission equivalent annual savings. Second, the paper addresses the need to codify the cumulative impact of point thermal bridges through insulation. The results of laboratory tests and computer simulations isolating the impact of these thermal bridges in low-slope roof assemblies are presented. Demonstrating that although point thermal bridges are absent in most current codes and standards, their impact is substantial and should be accounted for to maximize energy efficiency and minimize condensation potential.