The 2018 IECC is the legally mandated baseline for all residential construction and major renovations in the state of Texas. It is not a recommendation; it is a structural mandate designed to reduce the state's crippling summer grid strain.
Mandatory Air Sealing
The 2018 update was ruthless regarding drafts. It legally requires houses in Zone 3A (DFW) to test at 3 ACH50 (Air Changes per Hour at 50 Pascals).
Verification: Blower Door TestDuct Leakage Limits
Ducts located outside the conditioned space (in your 140°F attic) must be tested to prove they leak less than 4 CFM per 100 square feet of living space. If they leak more, your HVAC is actively cooling the neighborhood.
Verification: Duct Blaster TestYou cannot hit "3 ACH50" simply by throwing more fiberglass into your attic. It requires physical expanding foam to seal around your HVAC registers, can lights, plumbing stacks, and wire top-plates before any insulation is blown.