ASHRAE-90.1-2022- - Page 032
Extracted Content
face of the building envelope . Examples of linear thermal bridges include edges of floors, balconies, columns and beams in the plane of an assembly, parapets, roof-wall-floor intersections, fenestration interfaces, shelf angles, and similar conditions not otherwise defined as a clear field thermal bridge or point thermal bridge . point thermal bridge: a discrete element that penetrates the insulation in the building envelope . Examples of point thermal bridges include a beam penetrating a wall, a column penetrating a roof or floor, and an anchor or connection used to attach an element to the building and not otherwise defined as a clear field thermal bridge or linear thermal bridge . The cross-sectional area of the point thermal bridge is measured at the outer surface of the outermost layer of insulation that is penetrated by the element.
thermal conductance (C-factor): time rate of steady-state heat flow through unit area of a material or con- struction, induced by a unit temperature difference between the body surfaces (Btu/h·ft [2] ·°F). Note that the C-factor does not include soil or air films.
thermal resistance (R-value): the reciprocal of the time rate of heat flow through a unit area induced by a unit temperature difference between two defined surfaces of material or construction under steady-state conditions (h·ft [2] ·°F/Btu).
thermal transmittance (U-factor): heat transmission in unit time through unit area of a material or construc- tion and the boundary air films, induced by unit temperature difference between the environments on each side (Btu/h·ft [2] ·°F).
thermally effective panel surface: any exterior surface of a panel that is intended to transfer heat between the panel and the occupants and/or the indoor space .
thermally ineffective panel surface: any exterior surface of a panel that is not intended to transfer heat between the panel and the occupants and/or the indoor space .
thermostat: an automatic control device used to maintain temperature at a fixed or adjustable set point .
thermostatic control: an automatic control device or system used to maintain temperature at a fixed or adjustable set point .
tinted: (as applied to fenestration ) bronze, green, blue, or gray coloring that is integral with the glazing material. Tinting does not include surface-applied films such as reflective coatings, applied either in the field or during the manufacturing process.
toplighting: lighting building interiors with daylight admitted through fenestration, such as skylights and roof monitors, located on the roof .
total system performance ratio (TSPR): ratio of the sum of a building’s annual heating and cooling load in kBtu to the sum of annual energy input of the building mechanical systems, where the input units are in accordance with Section L5.
transfer air: air transferred from one room to another through openings in the room envelope, whether it is transferred intentionally or not. The driving force for transfer air is generally a small pressure differential between the rooms, although one or more fans may be used.
transformer: a piece of electrical equipment used to convert electric power from one voltage to another voltage.
dry-type transformer: a transformer in which the core and coils are in a gaseous or dry compound.
trim compressor: a compressor that is designated for part-load operation, handling the short-term variable trim load of end uses in addition to the fully loaded base compressors.
TSPR reference building design: a computer representation of a hypothetical building design based on modifications to the proposed design in accordance with Section L4.3. This representation is used as the basis for calculating the mechanical total system performance ratio for determining alternative mechanical system performance in accordance with Section 6.6.2.
U-factor: see thermal transmittance .
unconditioned space: see space .
unenclosed space: a space that is not an enclosed space .
unitary air conditioners: one or more factory-made assemblies that normally include an evaporator or cooling coil and a compressor and condenser combination. Units that perform a heating function are also included.
30 ANSI/ASHRAE/IES Standard 90.1-2022 (I-P)