Envelope requirements are keyed to climate zone. IECC C402 sets minimum insulation R-values and maximum assembly U-factors for roofs, walls, and floors, plus fenestration U-factor and SHGC limits, and continuous-air-barrier and air-leakage requirements. You can comply prescriptively (meet each value) or through a trade-off path such as total building performance or a COMcheck envelope analysis.
The common mistake is an assembly or window specification that doesn't meet the zone's values, or a set with no continuous-air-barrier detail at all.
Reviewers check the assemblies and fenestration against the climate-zone tables — or against the attached COMcheck report if you're trading off — and look for the air-barrier documentation, which is easy to leave off.
This guide describes the model code for general understanding and is not a substitute for the adopted code and amendments enforced by your local authority having jurisdiction. Verify all figures against your jurisdiction's codes of record.