Building codes set energy efficiency requirements but do for greenhouse gas emissions associated with other building lifecycle stages. Quantifying the relationship between envelope embodied carbon and thermal performance is critical to assess potential limits on embodied carbon and inform decarbonization of the whole building lifecycle. In this paper, we calculate embodied carbon associated with the product stage of insulation in energy code-compliant assemblies. While our findings concern assemblies that follow typical practices represented in the energy codes, our methods can be applied more broadly. We use publicly available data for materials covering a wide range of global warming potentials (GWPs) to model cavity insulation, continuous insulation, and combinations of the two, for roof, wall, and floor assemblies in the prescriptive tables of ASHRAE Standard 90.1-2019 for all building types and climate zones. Although not all materials apply to all assemblies or to both cavity and continuous insulation, this method produces numerous potential insulating approaches. For each assembly, we present the full range of computed GWP values, highlighting both typical and lower-GWP approaches, and develop explicit quantitative relationships between GWP and Ufactor. We also discuss important potential applications of our findings to decarbonization of new construction.