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Term

Definition

effective leakage area

A common term used to describe air flow at a pressure by equating it to an equivalent size

hole in an elliptical nozzle that would pass the same air flow at the same test pressure. It is

usually taken at 4 Pa and incorporates a 1.0 discharge coefficient. It is typically about half the

size of an equivalent leakage area that describes the same air flow rate. See ASTM E779-10,

eq. (5).

enclosure

The surface bounding a volume, which is connected to outdoors directly. For example an

apartment whose only access to outdoors was through a doorway that leads directly outdoors.

Or, a building with a series of apartments or offices whose only access to the outdoors is

through a common hallway then the enclosure would be the volume that bounds all of the

apartments or offices.

Envelope

The surfaces composed of floor and walls and floors that separate the test volume from

volume surrounding the test volume. Also see” enclosure”

Equivalent Leakage Area

(ELA or EqLA)

In layman’s terms, the ELA is the size of hole we’d have if all the building’s cracks and holes

could somehow be brought together. Also called: Whole Room Leakage and includes leaks

through the ceiling and below the ceiling (BCLA). In CA2001 we measure this in units of ft

. or

. at a reference pressure in Pascals (Pa).

In Engineer’s terms: the equivalent size of hole required in a flat plate to give the same flow

rate having a discharge coefficient of 0.61 and taken at the Reference Pressure.

This ELA is sometimes called the EqLA or Canadian ELA because it was first used in the

Canadian GSB air leakage standard for houses. This ELA enjoys worldwide acceptance by most

testers, even in the US.

This ELA should not be confused with another ELA that is often called the EfLA or Effective

Leakage Area. It is very unfortunate that both these ELA’s have the same acronym of ELA. The

EfLA was developed for the US ASTM Standard and is smaller than the EqLA by at least a factor

of 0.61 because it uses a discharge coefficient of 1.0. This EfLA is sometimes called the LBL or

Lawrence Berkley Labs ELA because it was developed there and is used in the LBL natural

airchange model that enjoys wide usage- apart from that usage, the EfLA is not used very

much but the existence of both can create huge problems that are totally lost on some users.

When it is taken at a reference pressure of 75 Pa, it is often referred to as EqLA75. EqLA is

typically about twice the size of an effective leakage area that describes the same air flow rate.

See ASTM E779-10, eq. (5).

Fan Pressure

The pressure difference between inside the door fan and the surrounding air. This pressure

can be read as “PrB” from Channel B on the DM-2. It is used by the computer to calculate the

air flow rate through the Door Fan.

Fan Top

Part on the fan where the fan’s tubing, Control Cable, and power connections are.

HVAC

Heating Ventilating and Air conditioning system.

Leakage

A general term used to describe holes or the area of holes in or around an enclosure.

Leakage Area

This is the same as “Leakage” but expressed in ft

or m

micromanometer

A digital gauge that is capable of reading in tenths of a Pascal.

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