NEBB BET CP key terms

A continuous building assembly that resists uncontrolled air movement between conditioned and unconditioned spaces, typically made of membranes, sealants, and rigid materials joined into one sealed system.

The condition in which all air barrier components overlap and seal to one another across walls, roofs, floors, and penetrations so no unintended gaps interrupt the enclosure's airtight boundary.

Unintended airflow through cracks, joints, and porous paths in the building enclosure, driven by pressure differences from wind, stack effect, or mechanical systems.

The measured volume of air passing through the enclosure per unit of time at a specified pressure difference, often normalized by floor area or envelope area for comparison between buildings.

A material installed behind cladding to shed bulk water that penetrates the outer facade, protecting sheathing and framing while allowing incidental moisture vapor to escape.

The surface within a wall assembly where liquid water is collected and directed downward and outward to weep holes or the exterior, usually formed by the water-resistive barrier.

Formed metal, membrane, or sealant components that redirect water at joints, penetrations, and terminations so it cannot enter the assembly or flow behind cladding.

A localized path of high heat conductance through the enclosure, such as a steel stud, slab edge, or balcony, that bypasses insulation and lowers overall thermal performance.

Insulation installed as an uninterrupted layer outside or across structural framing, reducing thermal bridging and improving effective R-value of the assembly.

The rate of heat flow through a unit area of an assembly per unit temperature difference across it, expressed as U-value and including all layers and bridging effects.

A measure of thermal resistance of a material or assembly, indicating how well it slows heat conduction; higher values mean better insulating performance under stated conditions.

The change of water vapor into liquid when air contacts a surface cooled below its dew point, a key risk inside wall cavities and on cold glazing or frames.

The temperature at which air reaches saturation and water vapor begins to condense, determined by the air's moisture content and pressure.

A material that limits diffusion of water vapor through an assembly, placed to keep moisture from condensing on cold surfaces within the wall or roof.

The coordinated design strategy of controlling rain entry, vapor diffusion, air leakage, and drying potential so enclosure assemblies remain below harmful moisture levels.

The practice of closing gaps around pipes, ducts, conduits, and fasteners that pass through air or water barriers, preserving the barrier's performance at those interruptions.

The junction where two different enclosure assemblies or materials meet, such as wall-to-roof or window-to-wall, requiring careful integration of air, water, and thermal control layers.

A calibrated fan temporarily mounted in a doorway that pressurizes or depressurizes a building to measure total air leakage and locate leaks under controlled pressure.

The airflow in cubic feet per minute required to hold a building at 50 pascals of pressure difference during a blower door test, a standard metric of airtightness.

The overall resistance of a completed building envelope to air leakage, quantified by a blower door test and often expressed per unit of envelope or floor area.

The difference in static pressure between two zones, such as inside and outside, that drives air movement through the enclosure and is the basis for leakage testing.

An instrument, often a digital manometer, that measures small pressure differences during enclosure testing so airflow and leakage results can be referenced to a known pressure.

The documented comparison of an instrument's readings against a known reference standard to confirm accuracy within tolerance before and during testing.

A device that measures air velocity at a point or across an opening, used to verify airflow at fans, grilles, and leakage paths during enclosure and HVAC testing.

The quantified range within which a measured test result is expected to lie, accounting for instrument accuracy, environmental variation, and procedural limitations.

The natural pressure difference existing between zones before test equipment is operated, measured so test-induced pressures can be corrected for wind and stack effects.

Vertical air movement caused by indoor-outdoor temperature and density differences, producing upward flow in tall spaces and driving infiltration or exfiltration through the enclosure.

Pressure exerted on the enclosure by wind, which stresses cladding, glazing, and sealants and must be considered when interpreting field leakage and structural performance.

A full-scale or representative section of the enclosure built for laboratory or field testing, allowing performance verification of assemblies and details before full construction.

A controlled enclosure or laboratory apparatus that applies specified air pressure, water spray, or temperature conditions to a specimen while performance is observed and recorded.

A procedure that applies controlled water spray and pressure difference to an assembly or mockup to determine whether water crosses the inner face of the enclosure.

A small opening at the base of a cavity or cladding system that allows collected water to drain outward and also permits pressure equalization and drying airflow.

A cladding system with a vented cavity designed so air pressure in the cavity nearly matches exterior pressure, reducing the driving force that pushes rain inward.

The amount of water vapor present in air expressed as a percentage of the maximum the air could hold at that temperature, influencing condensation risk within assemblies.

A noncontact survey technique that images surface temperature differences to reveal insulation gaps, thermal bridges, air leakage paths, and hidden moisture in the enclosure.

The formal document recording test scope, methods, instruments, conditions, measured results, deviations, and conclusions, forming the record of enclosure performance verification.