Namesort ascending Definition

abbr. Typical Meteorological Year

A data set used to create weather profiles for specific locations. TMY data is frequently used in building simulations and by designers of solar energy systems. Different data sets are indicated by number (TMY2, TMY3).

Through-Wall Flashing

Flashing that extends completely through a wall system. Designed and applied in combination with counter-flashings, to prevent water which may enter the wall above from proceeding downward in the wall or into a roof deck or roofing system.

Thermal Drift

The loss of R-value over time in foam insulation that contains captive blowing agents (extruded polystyrene insulation, PIC, ccSPF). Air enters the cells of the foam, diluting or replacing the lower-conductivity blowing agent. The rate and extent of thermal drift depends on multiple factors including exposure conditions, the thickness of installed insulation, and the particular chemical composition of a given foam product.

Thermal Control Layer

The component or components that are designed and installed in an assembly to control the transfer of thermal energy (heat). Typically these are comprised of insulation products, radiant barriers, or trapped gaps filled with air or other gases.

Thermal Bridge

A material with higher thermal conductivity transferring heat through an assembly with substantially lower thermal conductivity.  For example, a steel stud in a wall will transfer more heat than bthe surrounding insulation, reducing the overall thermal control of the system.

Thermal Boundary

The layer in a building enclosure that controls the transfer of energy (heat) between the interior and the exterior. It is a component of the building enclosure and it may (but does not have to) align with the pressure boundary.


abbr. testing, adjusting and balancing

The three major steps used to achieve proper operation of heating, ventilating, and air conditioning (HVAC) systems. Some contractors employ TAB specialists to optimize HVAC performance, especially in commercial buildings.


An agent (e.g., detergent) that, when mixed with water, breaks the surface tension of water drops, thus enabling easier absorption of water through a material.  Without surfactants, water would have a greater tendency to remain as drops on the surface of a given material.


A potentially harmful accumulation of water-soluble salts that re-crystalize just beneath a masonry, stucco, or concrete surface as moisture in the wall evaporates leaving the salts behind.


One of a series of wood or light steel vertical structural members placed as supporting elements in walls and partitions.


An exterior cladding formed in place on the wall and made of inorganically bonded sand and small aggregate. Typically Portland cement-based, but with additives of lime, surfactants, water repellents, etc.

State Change

Matter exists in three states: solid, liquid, and gas. A state change is a transition from one state to another. Examples include boiling/evaporation and condensation (liquid/gas), freezing and melting (solid/liquid), and sublimation/frost formation (solid/gas). Energy must be absorbed or released into the matter for a state change to occur.

Stack Effect

Air movement caused by warmer air rising and colder air falling. This generates small but steady pressures in direct relation to the size of the temperature difference and the height of the column of air. The resulting pressure differences can lead to air leakage and generate unplanned air flows that result in indoor air quality problems within buildings.

Spectrally Selective Glazing

A type of glazing that reduces solar gain while still providing daylighting. Spectrally selective glazing has low solar heat gain coefficients (SHGC), high visible light transmittance (VT) and usually low U-values.

Specific Heat Capacity

The measure of the amount of heat that a unit mass of dry material can store. It is typically defined as the heat energy required to raise the temperature of 1 g of material by 1 degree Kelvin.


A fragment of material, such as concrete or masonry, detached from a larger mass by a physical blow, freeze-thaw cycles, high levels of compression, or subfluorescence.

Sourced Drained

Describes a rain control strategy that uses the face-sealed approach on the body of an assembly, and the drained approach at the joints or penetrations that are assumed to be entry points for water. Many windows and some EIFS assemblies use this approach.

Smoke Puffer

See Smoke Pencil.

Smoke Pencil

A handheld device used to identify drafts and air leaks. A small amount of smoke is produced and observed in order to see the direction and location of air movement.

Variants: air current tester, smoke puffer, puffer stick


abbr. specific leakage area

A metric calculated by dividing the effective leak area (ELA) by the conditioned floor area. The ELA is the area of a theoretical hole in the building enclosure that would leak as much air as all of the building’s actual holes at a pressure difference of 4 Pa. SLA is usually reported in square inches of leakage per square foot of conditioned floor area.


abbr. structural insulated panel system

A building system using structural insulated panels. SIPS may be used for walls, roofs, exposed floors, or complete building enclosures. SIPS are not recommended for below-grade construction.


abbr. Structural Insulated Panel Association

A non-profit trade association representing manufacturers, suppliers, dealer/distributors, design professionals, and builders who provide or use structural insulated panels. SIPA provides an industry forum for promotion, communication, education, quality assurance, and technical and marketing research.


abbr. structural insulated panels

Panels consisting of an insulating foam core sandwiched between two structural facings, typically oriented strand board (OSB). Used in residential and light commercial construction.


A type of cladding system covering the outside wall and forming the exterior finish. May be made of horizontal weatherboards, vertical boards with battens, shingles, or other material.

Related source: IRC FAQ: Cladding Attachment Over Insulating Sheathing


abbr. système international d'unités or International System of Units

The current form of the metric system; more generally, a system of units of measurement devised around seven base units and the number ten. Globally, the SI is the most common measurement system used for commercial and standards activities. Other common systems of measurement include imperial units and U.S. customary units.


abbr. solar hot water


A metric of a glazing or window's ability to reduce solar heat gain. More specifically, the fraction of incident solar radiation admitted through a window. SHGC is expressed as a number between 0 and 1. The lower a window's SHGC, the less solar heat it transmits. Exterior temperature has a small influence on the result, and large angles of incidence will result in lower SHGCs than more normal angles.

Sheathing Membrane

A generic term for a membrane layer that resists the passage of liquid water (and possibly air and vapor) through vertical, drained surfaces. Asphalt-impregnated building papers and felts and polymeric housewraps are the most common products available, but peel and stick air-water-vapor barrier membranes, trowel applied air and water barriers, etc. are currently available.


A material used to provide structural stiffness to the wall framing and to provide structural backing for the cladding and sheathing paper. Typical materials are OSB (oriented strand board), plywood, or various forms of gypsum board.

Semi-Rigid Insulation

A type of insulation that is sold in formed boards composed of mineral fibers (typically glass or rock wool). Normally used for its non-combustible properties.

Related source: RR-1104: Hygrothermal Analysis of Exterior Rockwool Insulation, BSI-068: Rocks Don't Burn


abbr. seasonal energy efficiency ratio

An energy rating metric for cooling systems (air conditioners). SEER reports the cooling capacity (in Btu/hr) per Watt of electricity used in the system (fans, compressor, controls) when tested under conditions of 80°F indoor temperature with 50% indoor RH and 82°F outdoor temperature.


A flexible, polymer-based elastomeric material that is used in the assembly of the building enclosure to seal gaps, seams, or joints, making them waterproof or airtight (as part of the air or water control layers) or to provide a clean finish. Sealants are typically applied wet and may be tooled before curing to form a durable but flexible seal.

Variant: Caulking



abbr. supply air

Rough Opening

The opening in a wall into which a door, window, or other enclosure component is to be installed.

Rigid Insulation

Rigid board material that provides thermal resistance. Foam plastics such as expanded polystyrene (EPS), extruded polystyrene (XPS), and polyisocyanurate are commonly used.


abbr. relative humidity

See Relative Humidity.


abbr. Residential Energy Service Network

In April 1995, the National Association of State Energy Officials (NASEO) and Energy Rated Homes of America founded the Residential Energy Services Network (RESNET) to develop a national market for home energy rating systems and energy efficient mortgages.

Relative Humidity

The ratio (expressed as a percentage) of the amount of moisture within the air to the maximum amount of moisture that the air could possibly contain at a specific temperature.

Raised Heel Truss

A truss that has been fitted with a vertical member between the top and bottom truss cords, raising the top chord. The primary advantage of this strategy is to allow full-depth, uncompressed wall-to-wall insulation of the attic floor, reducing heat gain/ loss and mitigating the potential for ice dams.


Rainwater Boundary

The rainwater boundary (comprised of one or several materials and formed into planes to create a three dimensional boundary) is the boundary beyond which rainwater is not intended to penetrate or beyond which damage can likely be expected to occur if penetration were to occur.