BPI IDL study guide
BPI IDL · Work through your exam, one topic at a time.
The Infiltration & Duct Leakage (IDL) credential appears in the Building Performance Institute's published list of certifications, where it is named "Infiltration & Duct Leakage" and linked from BPI's Resources section alongside other individual certifications such as Building Analyst Technician, Energy Auditor, Air Leakage Control Installer, and Healthy Home Evaluator. BPI describes its mission as advancing the home performance industry through nationally recognized standards and credentials intended to help ensure homes are comfortable, healthy, safe, durable, and energy efficient, and it presents itself as "The symbol of excellence for home performance professionals." This independent study page is not affiliated with or endorsed by BPI. The BPI IDL study guide has 4 sections and about 1,394 words.
01Air Leakage and Duct Leakage Testing Fundamentals
A building envelope and its duct system both leak, and the two leaks have different consequences. Envelope leakage drives infiltration, which affects heating and cooling loads, moisture transport, and indoor air quality.
363 words, about 2 min02Blower Door and Duct Leakage Measurement Procedures
A blower door test requires a calibrated fan, a manometer measuring both building pressure and fan pressure (or fan flow), and a building prepared in a defined state: exterior doors and windows closed, interior doors in a specified position, combustion appliances and exhaust fans off, and openings to unconditioned space (attic hatches, crawlspace doors) in their normal condition. The candidate must know that the test measures the building pressure relative to outdoors, typically with a reference tube run outside, and that fan flow is derived from the fan's calibration curve at the measured fan pressure.
385 words, about 2 min03Building Envelope and Duct System Diagnostics
Diagnostics go beyond a single number. Pressure mapping with a manometer reveals which zones are connected: a closed interior door with a large pressure difference across it indicates a blocked return path, while a small difference suggests transfer openings.
347 words, about 2 min04Documentation, Standards, and Safety
Documentation turns a measurement into evidence. A complete record includes the test standard and version referenced, the date and time, weather conditions (especially wind and indoor-outdoor temperature difference), the building preparation state, instrument make, model, and calibration date, the reference pressure used, the raw multi-point data, the fitted curve and derived results, and any corrections applied.
299 words, about 1 min