When to do a blower door test?

When to do a blower door test depends on your goal, but there are several ideal times. For new construction, code requires a blower door test after all air sealing, insulation, windows, and exterior doors are installed but before final certificate of occupancy, typically near end of construction after drywall is complete and all penetrations sealed. Savvy builders do two tests, one at rough-in stage after sheathing and air barrier installed but before drywall to find and fix major leaks easily, and final test for code compliance. For existing homes, best time is during a comprehensive home energy audit when you want to assess efficiency, before and after air sealing work to measure improvement, when you experience drafts, high energy bills, ice dams, or comfort issues, or before major renovations that affect air barrier. Also do blower door test when buying a home to assess energy performance, after major air sealing or insulation upgrade to verify work, and in winter or cold weather when stack effect makes leaks easier to feel, though test can be done any season. Avoid testing during high winds over 15 mph or extreme temperatures which affect accuracy.