BPI IDL flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

CFM50

The blower-door airflow required to maintain a 50 Pa pressure difference across the building envelope; the primary single-point envelope tightness metric.

ACH50

Air changes per hour at 50 Pa, calculated as CFM50 times 60 divided by conditioned volume in cubic feet; a size-normalized envelope leakage metric.

Power law leakage

Leakage airflow relates to pressure by Q equals C times pressure difference raised to exponent n; n near 0.5 is orifice flow and near 1.0 is crack flow.

Effective leakage area

ELA converts measured leakage into an equivalent orifice area, commonly referenced at 4 Pa, allowing comparison of envelope tightness across homes.

CFM25

The duct-leakage reference airflow at 25 Pa pressure difference, used for total duct leakage and leakage-to-outdoors reporting.

Duct leakage percentage

Duct leakage CFM25 divided by system airflow at the same pressure, expressed as a percent; normalizes leakage to system size.

Infiltration load

Outdoor air entering through envelope leaks that must be heated or cooled; increases energy use and can carry moisture and pollutants indoors.

n-factor

A climate-dependent divisor used to estimate natural air changes from ACH50; typical values range from about 10 to 20.

Blower door baseline

Static pressure readings recorded before the fan runs, then subtracted from test readings to remove stack and wind bias.

Multi-point test

Recording airflow at several induced pressures, then fitting the power law to derive C and n for extrapolation to other pressures.

Single-point test

A blower-door test using one induced pressure near 50 Pa, valid only when wind is low and the reading is stable.

Duct pressurization setup

Sealing registers and connecting the test fan to the air handler or a register, then pressurizing the duct system to 25 Pa.

Total duct leakage

Duct leakage measured at 25 Pa with the house open to outdoors, capturing leakage to both conditioned space and outside.

Leakage to outdoors

Duct leakage measured at 25 Pa with the house sealed and pressurized, isolating leakage paths that connect ducts to outside.

Reference pressure tap

The hose connection sensing outdoor or reference pressure; if obstructed or misrouted, every gauge reading becomes unreliable.

Fan ring selection

Choosing the correct gauge ring for the expected airflow range; a wrong ring or kinked hose corrupts all airflow readings.

Pressure pan test

A pan placed over a register or outlet to read pressure while the house is depressurized; elevated readings indicate a leak path.

Zonal pressure testing

Measuring pressure differences between rooms or zones with doors closed to locate connected zones and hidden leakage paths.

Thermal imaging survey

Infrared camera use during depressurization to reveal air leakage and missing insulation, since leaks appear as temperature anomalies.

Smoke pencil tracing

A smoke source moved along suspected paths to visualize leakage direction and confirm ambiguous pressure readings.

Unconditioned duct leakage

Leakage from ducts in attics, crawlspaces, or garages; it is effectively outdoor leakage and is the highest-priority repair.

Return-side leakage

Leaks on the return duct that can draw attic or garage air into the supply stream, harming indoor air quality and pressure balance.

Room pressure imbalance

Closed-door pressure differences caused by supply and return mismatch, producing comfort complaints and possible backdrafting.

Combustion appliance spillage

Flue gas escaping into the space rather than up the vent; depressurization from testing can cause it, so appliances are monitored.

Test conditions record

Documentation of indoor and outdoor temperature, wind, baseline pressures, gauge model, ring, and fan configuration for each test.

Reference pressure statement

Every reported airflow must state the pressure at which it was measured, such as CFM50 or CFM25, to be meaningful.

ASTM E779

A standard test method for determining air leakage rate of buildings by fan pressurization, commonly cited for envelope testing.

ASTM E1554

A standard test method for determining air leakage of HVAC air distribution systems, commonly cited for duct leakage testing.

Pre/post retrofit comparison

Reporting before and after values measured with the same protocol so that improvement can be verified and attributed.

Anomaly documentation

Recording open windows, obstructed registers, wind gusts, or other conditions that could invalidate results, along with corrective actions.

Raw data retention

Keeping gauge readings, calculations, and notes so third-party verification and program compliance can audit the result.

Blower door safety rule

Never leave the blower door running unattended; secure the panel and fan and protect openings and occupants during testing.