At what stage of construction is a blower door test done?

At what stage of construction a blower door test is done includes two key stages for best quality control. For code compliance required by International Energy Conservation Code, the final blower door test is done near the end of construction after all components affecting air barrier are complete, including exterior sheathing and house wrap, windows and exterior doors installed and flashed, all plumbing, electrical, and HVAC penetrations sealed, attic and wall insulation installed, drywall installed and taped, and interior air sealing complete, but before final occupancy and usually before interior trim is fully complete so minor sealing can still be done. However, high performance builders do a preliminary blower door test at mid-construction stage, often after sheathing, windows, and rough-in air sealing but before drywall and insulation, sometimes called rough-in or pre-drywall blower door test. This early test allows you to find major leaks while they are still accessible and easy to fix, saving time and cost. Final test is then done to verify compliance. Some programs like Energy Star require both rough-in and final testing. So best practice is test twice, once at rough-in and once at final, with final official test for certificate of occupancy.