annual fuel utilization efficiency (AFUE): an efficiency descriptor of the ratio of annual output energy to annual input energy as developed in accordance with the requirements of U.S. Department of Energy (DOE) 10 CFR Part 430.
automatic control device: a device capable of automatically turning loads off and on without manual intervention.
balancing, air system: adjusting airflow rates through air distribution system devices, such as fans and diffusers, by manually adjusting the position of dampers, splitter vanes, extractors, etc., or by using automatic control devices, such as constant air volume or variable-air-volume (VAV) boxes.
balancing, hydronic system: adjusting water flow rates through hydronic distribution system devices, such as pumps and coils, by manually adjusting the position valves or by
using automatic control devices, such as automatic flow control valves.
ballast: a device used in conjunction with an electric discharge lamp to cause the lamp to start and operate under the proper circuit conditions of voltage, current, wave form, electrode heat, etc.
baseline building performance: the annual energy cost for a building design intended for use as a baseline for rating above standard design.
budget building design: a computer representation of a hypothetical design based on the actual proposed building design. This representation is used as the basis for calculating the energy cost budget.
C-factor (thermal conductance): time rate of steady-state heat flow through unit area of a material or construction, induced by a unit temperature difference between the body surfaces. Units of Care W/m2·K. Note that the C-factor does not include soil or air films.
class of construction: for the building envelope, a subcategory of roof, above-grade wall, below-grade wall, floor, slab-ongrade
floor, opaque door, vertical fenestration, or skylight.
clerestory: that part of a building that rises clear of the roofs or other parts and whose walls contain windows for lighting
coefficient of performance (COP)-cooling: the ratio of the rate of heat removal to the rate of energy input, in consistent
units, for a complete refrigerating system or some specific portion of that system under designated operating conditions.
coefficient of performance (COP), heat pump-heating: the ratio of the rate of heat delivered to the rate of energy input, in consistent units, for a complete heat pump system, including the compressor and, if applicable, auxiliary heat, under designated operating conditions.
continuous insulation (c.i.): insulation that is continuous across all structural members without thermal bridges other than fasteners and service openings. It is installed on the interioror exterior or is integral to any opaque surface of the building envelope.
cooling design temperature: the outdoor dry-bulb temperature equal to the temperature that is exceeded by 1 % of the number of hours during a typical weather year.
cooling design wet-bulb temperature: the outdoor wet-bulb temperature for sizing cooling systems and evaporative heat
rejection systems such as cooling towers.
dead band: the range of values within which a sensed variable can vary without initiating a change in the controlled process.
degree-day: the difference in temperature between the outdoor mean temperature over a 24-hour period and a given
base temperature. For the purposes of determining building envelope requirements, the classifications are defined as
cooling degree-day base 10°C (CDD10): for any one day,
when the mean temperature is more than 10°C, there are
as many degree-days as degrees Celsius temperature
difference between the mean temperature for the day and
10°C. Annual cooling degree-days (CDDs) are the sum of
the degree-days over a calendar year.
heating degree-day base 18°C (CDD18): for any one day,
when the mean temperature is less than 18°C, there are as
many degree-days as degrees Celsius temperature difference
between the mean temperature for the day and 18°C.
Annual heating degree-days (HDDs) are the sum of the
degree-days over a calendar year.
demand: the highest amount of power (average kilowatts over an interval) recorded for a building or facility in a
selected time frame.
demand control ventilation (DCV): a ventilation system capability that provides for the automatic reduction of outdoor
air intake below design rates when the actual occupancy of spaces served by the system is less than design occupancy.
design capacity: output capacity of a system or piece of equipment at design conditions.
design conditions: specified environmental conditions, such as temperature and light intensity, required to be produced and
maintained by a system and under which the system must operate.
design energy cost: the annual energy cost calculated for a proposed design.
direct digital control (DDC): a type of control where controlled and monitored analog or binary data (e.g., temperature, contact closures) are converted to digital format for manipulation and calculations by a digital computer or microprocessor, then converted back to analog or binary form to control physical devices.
economizer, air: a duct and damper arrangement and automatic control system that together allow a cooling system to
supply outdoor air to reduce or eliminate the need for mechanical cooling during mild or cold weather.
economizer, water: a system by which the supply air of a cooling system is cooled indirectly with water that is itself cooled
by heat or mass transfer to the environment without the use of mechanical cooling.
efficacy (of a lamp): the ratio of the total luminous output of a lamp to the total power input to the lamp; typically expressed
in lumens per watt.
efficiency: performance at specified rating conditions.
emittance: the ratio of the radiant heat flux emitted by a specimen to that emitted by a blackbody at the same temperature
and under the same conditions.
energy cost budget: the annual energy cost for the budget building design intended for use in determining minimum compliance with this standard.
energy efficiency ratio (EER): the ratio of net cooling capacity in kWh to total rate of electric input in watts under designated operating conditions. (See coefficient of performance [COP-cooling.)
energy factor (EF): a measure of water heater overall efficiency.
envelope performance factor: the trade-off value for the building envelope performance compliance option calculated
using the procedures specified in Section 5. For the purposes of determining building envelope requirements, the classifications
are defined as follows:
base envelope performance factor: the building envelope
performance factor for the base design.
proposed envelope performance factor: the building
envelope performance factor for the proposed design.
F-factor: the perimeter heat loss factor for slab-on-grade floors, expressed in W/m·K.
fan system input kilowatts [kW]: the sum of the fan input kilowatts (kW) of all fans that are required to operate at fan system design conditions to supply air from the heating or cooling source to the conditioned space(s) and return it to the source or exhaust it to the outdoors.
fan system design conditions: operating conditions that can be expected to occur during normal system operation that result in the highest supply airflow rate to conditioned spaces served by the system.
fan system motor nameplate kilowatts: the sum of the motor nameplate kilowatts (kW) of all fans that are required to operate at design conditions to supply air from the heating or cooling source to the conditioned space( s) and return it to the source or exhaust it to the outdoors.
floor area, gross: the sum of the floor areas of the spaces within the building, including basements, mezzanine and intermediate-floored tiers, and penthouses with a headroom height of 2.3 m or greater. It is measured from the exterior faces of exterior walls or from the centerline of walls separating buildings, but excluding covered walkways, open roofed-over areas, porches and similar spaces, pipe trenches, exterior terraces or steps, chimneys, roof overhangs, and similar features.
gross building envelope floor area: the gross floor area of
the building envelope, but excluding slab-on-grade floors.
gross conditioned floor area: the gross floor area of
gross lighted floor area (aka gross lighted area -GLA): the gross floor area of lighted
gross semi-heated floor area: the gross floor area of semi-heated
flue damper: a device in the flue outlet or in the inlet of or upstream of the draft control device of an individual, automatically
operated, fossil fuel-fired appliance that is designed to automatically open the flue outlet during appliance operation
and to automatically close the flue outlet when the appliance is in a standby condition.
heat capacity (He): the amount of heat necessary to raise the temperature of a given mass 0.56°C. Numerically, the He per unit area of surface (kJ/m2’K) is the sum of the products of the mass per unit area of each individual material in the roof, wall, or floor surface multiplied by its individual specific heat.
heat trace: a heating system where the externally applied heat source follows (traces) the object to be heated, e.g., water
heating design temperature: the outdoor dry-bulb temperature equal to the temperature that is exceeded at least 99.6% of the number of hours during a typical weather year.
heating seasonal performance factor (HSPF): the total heating output of a heat pump during its normal annual usage period for heating (in Wh) divided by the total electric energy input during the same period.
high-frequency electronic ballast: ballasts that operate at a frequency greater than 20 kHz.
infiltration: the uncontrolled inward air leakage through cracks and crevices in any building element and around windows and doors of a building caused by pressure differences across these elements due to factors such as wind, inside and outside temperature differences (stack effect), and imbalance between supply and exhaust air systems.
installed interior lighting power: the power in watts of all permanently installed general, task, and furniture lighting systems and luminaires.
integrated part-load value (IPLV): a single-number figure of merit based on part-load EER, COP, or kW/ton expressing part-load efficiency for air-conditioning and heat pump equipment on the basis of weighted operation at various load capacities for the equipment.
isolation devices: devices that isolate HVAC zones so that they can be operated independently of one another. Isolation devices include, but are not limited to, separate systems, isolation dampers, and controls providing shutoff at terminal boxes.
lighting power allowance: interior lighting power allowance: the maximum lighting power in watts allowed for the interior of a building.
exterior lighting power allowance: the maximum lighting power in watts allowed for the exterior of a building.
lighting power density (LPD): the maximum lighting power per unit area of a building classification of space function.
mean temperature: one-half the sum of the minimum daily temperature and maximum daily temperature.
metering: instruments that measure electric voltage, current, power, etc.
motor power, rated: the rated output power from the motor. nameplate kW: the nominal motor kW rating stamped on the motor nameplate.
nameplate rating: the design load operating conditions of a device as shown by the manufacturer on the nameplate or otherwise marked on the device.
non-recirculating system: a domestic or service hot-water distribution system that is not a recirculating system.
nonstandard part-load value (NPLV): a single-number part-load efficiency figure of merit calculated and referenced to conditions other than IPLV conditions, for units that are not designed to operate at ARl Standard Rating Conditions.
optimum start controls: controls that are designed to automatically adjust the start time of an HVAC system each day with the intention of bringing the space to desired occupied temperature levels immediately before scheduled occupancy.
overcurrent: any current in excess of the rated current of
equipment or the ampacity of a conductor. It may result from
overload, short circuit, or ground fault.
packaged terminal air conditioner (PTAC): a factory selected
wall sleeve and separate un-encased combination of
heating and cooling components, assemblies, or sections. It
may include heating capability by hot water, steam, or electricity
and is intended for mounting through the wall to serve
a single room or zone.
packaged terminal heat pump (PTHP): a PTAC capable of
using the refrigerating system in a reverse cycle or heat pump
mode to provide heat.
party wall: a fire wall on an interior lot line used or adapted for
joint service between two buildings.
Performance Rating Method: a calculation procedure that
generates an index of merit for the performance of building
designs that substantially exceeds the energy efficiency levels
required by this standard.
photosensor: a device that detects the presence of visible light,
infrared (IR) transmission, and/or ultraviolet (UY) energy.
plenum: a compartment or chamber to which one or more
ducts are connected, that forms a part of the air distribution
system, and that is not used for occupancy or storage. A
plenum often is formed in part or in total by portions of the
process energy: energy consumed in support of a manufacturing,
industrial, or commercial process other than conditioning
spaces and maintaining comfort and amenities for the occupants
of a building.
process load: the load on a building resulting from the
consumption or release of process energy.
projection factor (PF): the ratio of the horizontal depth of the
external shading projection divided by the sum of the height of
the fenestration and the distance from the top of the fenestration to the bottom of the farthest point ofthe external shading
projection, in consistent units.
proposed building performance: the annual energy cost
calculated for a proposed design.
proposed design: a computer representation of the actual
proposed building design or portion thereof used as the basis
for calculating the design energy cost.
pump system power: the sum of the nominal power demand
(nameplate kW) of motors of all pumps that are required to
operate at design conditions to supply fluid from the heating
or cooling source to all heat transfer devices (e.g., coils, heat
exchanger) and return it to the source.
purchased energy rates: costs for units of energy or power
purchased at the building site. These costs may include energy
costs as well as costs for power demand as determined by the
radiant heating system: a heating system that transfers heat to
objects and surfaces within the heated space primarily (greater
than 50%) by infrared radiation.
rated R-value of insulation: the thermal resistance of the insulation
alone as specified by the manufacturer in units ofm2·KJ
W at a mean temperature of 24°C. Rated R-value refers to the
thermal resistance of the added insulation in framing cavities
or insulated sheathing only and does not include the thermal
resistance of other building materials or air films.
recirculating system: a domestic or service hot-water distribution
system that includes a closed circulation circuit
designed to maintain usage temperatures in hot-water pipes
near terminal devices (e.g., lavatory faucets, shower heads) in
order to reduce the time required to obtain hot water when the
terminal device valve is opened. The motive force for circulation
is either natural (due to water density variations with
temperature) or mechanical (recirculation pump).
re-cooling: lowering the temperature of air that has been previously
heated by a mechanical heating system.
reflectance: the ratio of the light reflected by a surface to the
light incident upon it.
re-heating: raising the temperature of air that has been previously
cooled either by mechanical refrigeration or an economizer
room cavity ratio (RCR): a factor that characterizes room
configuration as a ratio between the walls and ceiling and is
based upon room dimensions.
seasonal coefficient of performance-cooling (SCOPe): the
total cooling output of an air conditioner during its normal
annual usage period for cooling divided by the total electric
energy input during the same period in consistent units (analogous
to the SEER but in SI or other consistent units).
seasonal coefficient of performance-heating (SCOPH): the
total heating output of a heat pump during its normal annual
usage period for heating divided by the total electric energy
input during the same period in consistent units (analogous to
the HSPF but in SI or other consistent units).
seasonal energy efficiency ratio (SEER): the total cooling
output of an air conditioner during its normal annual usage
period for cooling (in Wh) divided by the total electric energy
input during the same period (in Wb).
shading coefficient (SC): the ratio of solar heat gain at normal
incidence through glazing to that occurring through 3 mm
thick clear, double-strength glass. SC, as used herein, does not
include interior, exterior, or integral shading devices.
site-recovered energy: waste energy recovered at the building
site that is used to offset consumption of purchased fuel or
electrical energy supplies.
site-solar energy: thermal, chemical, or electrical energy
derived from direct conversion of incident solar radiation at
the building site and used to offset consumption of purchased
fuel or electrical energy supplies. For the purposes of applying
this standard, site-solar energy shall not include passive heat
gain through fenestration systems.
solar heat gain coefficient (SHGC): the ratio of the solar heat
gain entering the space through the fenestration area to the
incident solar radiation. Solar heat gain includes directly
transmitted solar heat and absorbed solar radiation, which is
then re-radiated, conducted, or convected into the space.
conditioned space: a cooled space, heated space, or indirectly
conditioned space defined as follows:
1. cooled space: an enclosed space within a building
that is cooled by a cooling system whose sensible
output capacity exceeds 15 W/m2 of floor area.
2. heated space: an enclosed space within a building
that is heated by a heating system whose output
capacity relative to the floor area is greater than or
equal to the criteria in Table 3.1.
3. indirectly conditioned space: an enclosed space
within a building that is not a heated space or a
cooled space, which is heated or cooled indirectly
by being connected to adjacent space( s) provided:
a. the product of the U-factor(s) and surface
area(s) of the space adjacent to connected
space( s) exceeds the combined sum of the
product of the U-factor(s) and surface
area(s) of the space adjoining the outdoors,
unconditioned spaces, and to or from semi-heated
spaces (e.g., corridors) or
b. that air from heated or cooled spaces is
intentionaJ1y transferred (naturally or
mechanically) into the space at a rate
exceeding 3 ach (e.g., atria).
substantial contact: a condition where adjacent building
materials are placed so that proximal surfaces are contiguous,
being installed and supported so they eliminate voids between
materials without compressing or degrading the thermal
performance of either product.
tandem wiring: pairs of luminaires operating with lamps in
each luminaire powered from a single ballast contained in one
of the luminaires.
task lighting: lighting directed to a specific surface or area that
provides illumination for visual tasks.
thermal block: a collection of one or more HVAC zones
grouped together for simulation purposes. Spaces need not be
contiguous to be combined within a single thermal block.
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.
- liquid-immersed transformer: a transformer in which
the core and coils are immersed in an insulating liquid.
V-factor (thermal transmiuance): heat transmission in unit time
through unit area of a material or construction and the boundary
air films, induced by unit temperature difference between the
environments on each side. Units of U are W/m2·K.
unmet load hour: an hour in which one or more zones is
outside of the thermostat set point range.
unitary cooling equipment: 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.
unitary heat pump: one or more factory-made assemblies that
normally include an indoor conditioning coil, compressor(s),
and an outdoor refrigerant-to-air coil or refrigerant-to-water
heat exchanger. These units provide both heating and cooling
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.
vent damper: a device intended for installation in the venting
system of an individual, automatically operated, fossil-fuel fired
appiance 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.