Common Terminology for Home and Building Pressure Testing

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Accuracy – the degree of conformity of an indicated value to an accepted standard or true value. The degree of inaccuracy is known as the total measurement error and is the sum of bias error and precision (random) error.*


Air changes per hour – one of several metrics used to compare and evaluate the airtightness of homes and buildings.


Airtightness – a building’s ability to limit the amount of air leaking into and out of its interior spaces.


Air sealing – the process of installing materials to stop airflow between conditioned and unconditioned spaces of a home or building.


Airtightness testing – the evaluation of a building using a blower door to measure the amount of air leakage that occurs at a given pressure, typically 50 Pascals.


Bias or systematic error – a persistent difference between the true or actual value to be measured and the indicated value from the measuring system.  Errors of this type can be corrected by calibration.*


Blower door – a diagnostic tool that is used to help determine the amount of air leakage in a building.


Building envelope – the continuous barrier or shell that encloses occupant spaces in a home or building. Envelope components include: walls, floors, ceilings and other planes identified by a building analyst during a structural inspection.


Building science – the study of all systems within buildings, and how those systems work with one another to affect occupant comfort and overall energy usage for the structure.


Calibration – correcting or determining the error of an existing scale, or of evaluating one quantity in terms of readings from another.*


Conditioned space – areas inside a building that are intentionally heated or cooled.


Duct Blaster® – equipment manufactured by The Energy Conservatory (TEC) that is typically used for measuring duct leakage. Duct Blaster is a registered trademark of TEC.


Duct leakage testing – the evaluation of a building’s duct system for airtightness.


Duct leakage to outside – a method of measuring duct leakage that requires the use of both a blower door and a Duct Blaster® to measure the amount of air leaking to the outside.


Exfiltration – air flowing out of a building through unintentional holes and gaps.


Home performancea comprehensive whole-house approach to identifying and fixing comfort and energy efficiency problems in a home.


House as a system – how all the components within a building interact. Instead of looking at each component individually, analysts understand them as parts of a whole. Also see “home performance” and “building science.”


Indoor air qualitythe air quality within and around buildings, especially as it relates to the health and comfort of building occupants.


Infiltration – air flowing into the building through unintentional holes and gaps.


Multi-fan blower door test – a test performed with more that one blower door fan. This type of test is used for some multi-family buildings, and small and large commercial buildings.


Multi-point blower door test – a test performed at more that one test pressure, typically 6 to 8 pressures. This is done to determine the accuracy and repeatability of the test.


Precision – the closeness of agreement among repeated measurements of the same characteristic by the same method under the same conditions.*


Precision or random error – a statistical error that is caused by chance and is not recurring. Random errors cannot be corrected through calibration.*


Pressure – Absolute – normal force per unit area exerted by a fluid on a containing wall with respect to zero absolute pressure.*


Pressure – Ambient – the pressure in which a device operates.*


Pressure – Barometric – the pressure of the atmosphere relative to absolute pressure.*


Pressure – Differential – difference in pressure between any two points in a system.*


Pressure – Static – pressure at a point where the fluid element is in equilibrium.  Static pressure would be indicated by a pressure sensing instrument at rest with respect to the fluid.*


Pressure – Total – the pressure on a plane normal to the local flow direction.*


Pressure – Velocity – the net pressure increase that can be derived from the complete conversion of the velocity to pressure in a reversible process.*


Pressure boundary – the location where an air barrier is installed to create a boundary between interior and exterior air pressure differences. These differences occur due to temperature changes and weather factors.


Resolution – the smallest change a sensor is able to detect in the quantity that it is measuring.*


Sensitivity – the ratio of the change in indicated value to the change in measured value.*


Single-point blower door test – a test done at a single pressure, typically 50 Pascals.


Stack effectthe transfer of air into and out of buildings due to air buoyancy. Wherever there is a difference between indoor and outdoor air temperatures, air buoyancy occurs. Warmer air masses rise and exit the building, pulling cooler air masses inside – much like a chimney creating a draft.


Thermal boundary – the location where insulation is installed. Ideally the pressure boundary and thermal boundary will line up.


Uncertainty – an estimated value for the error in a measurement, which may be the  result of both systematic and random error.*


Unconditioned space – areas in a home or building that are not intentionally heated or cooled.


  • From ASHRAE Standard 41.3 – 2014 Standard Methods for Pressure Measurement.