ASHRAE-90.1-2022- - Page 033

Extracted Content

unitary heat pump: one or more factory-made assemblies that normally include an indoor conditioning coil, compressors, and an outdoor refrigerant-to-air coil or refrigerant-to-water heat exchanger. These units provide both heating and cooling functions.

unmet load hour: an hour in which one or more zones is outside of the thermostat set point plus or minus one half of the temperature control throttling range . Any hour with one or more zones with an unmet cooling load or unmet heating load is defined as an unmet load hour .

unregulated energy use: energy used by building systems and components that is not regulated energy use . (See regulated energy use .)

variable-air-volume (VAV) system: HVAC system that controls the dry-bulb temperature within a space by varying the volumetric flow of heated or cooled supply air to the space .

variable-refrigerant-flow (VRF) system: an engineered direct expansion (DX) multisplit system incorporating at least one variable capacity compressor distributing refrigerant through a piping network to multiple indoor fan-coil units, each capable of individual zone temperature control, through integral zone temperature control devices and common communications network. Variable refrigerant flow uses three or more steps of control on common, interconnecting piping .

vegetative roof system: vegetation, growth media, drainage system, and waterproofing over a roof deck.

vent damper: a device intended for installation in the venting system of an individual, automatically operated, fossil- fuel -fired appliance in the outlet or downstream of the appliance draft control device, which is designed to automatically open the venting system when the appliance is in operation and to automatically close off the venting system when the appliance is in a standby or shutdown condition.

ventilation: the process of supplying or removing air by natural or mechanical means to or from any space . Such air is not required to have been conditioned.

ventilation system motor nameplate horsepower (hp): the sum of the motor nameplate horsepower of all fans that are required to operate as part of the system .

verification and testing provider (V&T provider): an entity who completes the activities needed to implement the building functional performance testing ( FPT ) activities or verify that elements of the building project meet stated requirements.

vertical fenestration: all fenestration other than skylights . Trombe wall assemblies, where glazing is installed within 12 in. of a mass wall, are considered walls, not fenestration . For the purposes of determining building envelope requirements, the vertical fenestration classifications are defined as follows:

entrance door: any doorway, set of doors, turnstile, vestibule, or other form of portal that is ordinarily used to gain access by its users and occupants to the building or to individual tenant spaces accessed from the exterior. (See building entrance and door .)

fixed: all types of vertical fenestration, other than entrance door and operable, including, but not limited to, curtain walls, window walls, fixed windows, picture windows, glass block walls, nonopenable clerestory windows, roof monitors with nonopenable windows, and nonopenable sidelights and transoms.

operable: all vertical fenestration that opens, except entrance doors, including, but not limited to, casement windows, projecting windows, pivoting windows, horizontal sliding windows, vertical sliding windows, openable clerestory windows, openable sidelights and transoms, sliding glass doors, roof monitors with openable windows, and doors that are not entrance doors .

visible transmittance (VT): the ratio of visible radiation entering the space through the fenestration product to the incident visible radiation, determined as the spectral transmittance of the total fenestration system, weighted by the photopic response of the eye and integrated into a single dimensionless value.

voltage drop: a decrease in voltage caused by losses in the lines connecting the power source to the load.

VT: see visible transmittance .

walk-in cooler: an enclosed storage space of <3000 ft [2] that can be walked into and that is designed to maintain a space temperature of >32°F and  55°F.

walk-in freezer: an enclosed storage space of <3000 ft [2] that can be walked into that is designed to maintain a space temperature of  32°F.

wall: that portion of the building envelope, including opaque area and fenestration, that is vertical or tilted at an angle of 60 degrees from horizontal or greater. This includes above- and below-grade walls, between

ANSI/ASHRAE/IES Standard 90.1-2022 (I-P) 31