Glossary · Testing & air leaks

Duct leakage test

Also called: duct blaster test · Duct Blaster · duct pressurization test · duct tightness test · duct leakage · CFM25

A test that pressurizes your heating and cooling ducts with a calibrated fan to measure how much air escapes through leaks.

What it means

The tester seals the supply and return registers, connects a calibrated fan (often called a duct blaster) and holds the ducts at 25 pascals. The airflow needed to hold that pressure is the leakage, reported as CFM25. Total leakage counts every leak; a second version, leakage to outside, counts only air lost to attics, crawlspaces, garages or outdoors.

Why it matters in an audit

Leaky ducts waste heating and cooling you've paid for and can pull dusty or humid air from attics and crawlspaces into the house, so duct sealing is often a high-ranked audit recommendation.

Sources

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Related terms

Duct leakage to outside The part of duct leakage that escapes outside the heated and cooled space, into attics, crawlspaces, garages or outdoors.
Blower door test A test that uses a powerful, calibrated fan in an outside doorway to pull air out of the house and measure how leaky it is.
Pascal (Pa) and "50 Pa" A small unit of air pressure; airtightness tests hold a house at 50 pascals, about 1/2,000 of normal air pressure, so results can be compared.
Ducted heat pump A heat pump that heats and cools through ductwork, like central air conditioning, either on its own or paired with a furnace.
Air sealing Blocking the hidden gaps where air leaks in and out of a house, which cuts drafts, heating and cooling costs, and moisture problems.
Manometer A precise pressure gauge auditors use to read small pressure differences, in pascals, during blower door, duct leakage and combustion safety tests.

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