Glossary
A B C
D E F G
H
I J K
L M N
O P
Q R S
T U V
W X
Y Z
A
Air Barrier
Any part of the building shell
that offers resistance to air leakage. The air barrier is
effective if it stops most air leakage. The primary air
barrier is the most effective of a series of air barriers.*
Air changes at 50 pascals
(ACH50)
The number of times that the
complete volume of a home is exchanged for outside air when a
blower door depressurizes the home to 50 pascals.
Air Duct
A hollow tube (square or round)
that circulates air from a forced-air heating and/or cooling
system
to a room (supply duct) or returns air back to the main system
from a room (return duct).
Air handler
A steel cabinet containing a
blower with cooling and/or heating coils connected to ducts.
Assessment
The process of identifying energy
efficiency opportunities in buildings.
Annual fuel utilization
efficiency (AFUE)
A laboratory-derived efficiency
rating for heating appliances which accounts for chimney losses,
jacket losses, and cycling losses.
Air Leak
A hole, crack or gap where air can leak in or out of a house.
Air leaks can make a home feel drafty or uncomfortable and waste
energy.
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B
Backdrafting
Continuous spillage of combustion
gases from a combustion appliance.
Batt
A narrow blanket of fiberglass
insulation, often 14.5 or 22.5 inches wide.
Blower door
A device that consists of a fan, a
removable panel, and gauges used to measure and locate air
leaks.
Boot
A duct section that connects
between a duct and a register.
British thermal unit (Btu)
The quantity of heat required to
raise the temperature of one pound of water one degree
Fahrenheit.
Building Science
Branch of science dealing with
construction, maintenance, safety, and energy efficiency of
buildings.
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C
Capillary action
The ability of water to move
through materials, even upward against gravity, through small
tubes or spaces.
Capillary barrier
A material or air space designed
to stop capillary action from carrying water into a building.
Carbon dioxide
One of two main products of
complete combustion of a hydrocarbon (the other is water vapor).
Carbon monoxide
An odorless and poisonous gas
produced by incomplete combustion.
Caulking
A mastic compound for filling
joints and cracks.
Cellulose insulation
Insulation, packaged in bags for
blowing, made from newspaper or wood waste and treated with a
fire retardant.
CFM50
The number of cubic feet per
minute of air flowing through the fan housing of a blower door
when the house pressure is 50 pascals (0.2 inches of water).
This figure is the most common and accurate way of comparing the
airtightness of buildings that are tested using a blower door.
Coefficient of performance
(COP)
A heat pump or air conditioner's
output in watt-hours of heat moved divided by watt-hours of
electrical input.
Coil
A snakelike piece of copper tubing
surrounded by rows of aluminum fins that clamp tightly to the
tubing in order to aid in heat transfer.
Combustion air
Air that provides oxygen for
combustion.
Compressor
A motorized vapor pump that
compresses the gaseous refrigerant and sends it to the condenser
where collected heat is released.
Condense
when a gas turns into a liquid as
it cools, we say it condense. Condensation is the opposite
of evaporation.
Condenser
The coil in an air conditioning
system where the refrigerant condense and releases heat.
Conditioned
Intentionally heated or cooled
areas of a building are conditioned.
Conduction
Heat flow from molecule to
molecule in a solid substance.
Convection
The transfer of heat caused by the
movement of a fluid like water or air. When a fluid
becomes warmer it becomes lighter and rises.
Cooling load
The maximum rate of heat removal
required of an air conditioner when the outdoor temperature and
humidity are at the highest expected level.
Cost-effective
Having an acceptable payback,
return-on-investment, or saving-to-investment ratio.
Cubic foot per minute (cfm)
A measurement of air movement past
a certain point or through a certain structure.
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D
Degree-days
A measure of the temperature
element of climate produces by multiplying temperature
difference by time.
Depressurize
Cause to have a lower pressure or
vacuum with respect to a reference of a higher pressure.
Dew point
The warmest temperature of an
object in an environment where water condensation from the
surrounding air would form on that object.
Distribution system
A system of pipes or ducts used to
distribute energy.
Duct Blaster
A blower-door-like device used for
testing duct leakiness and air flow.
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E
Energy
A quantity of heat or work.
Energy consumption
The conversion or transformation
of potential energy into kinetic energy for heat, light,
electricity, etc.
Energy efficiency
Term describing how efficiently a
building component uses energy.
Energy efficiency ratio (EER)
A measurement of energy efficiency
for air conditioners. The EER is computed by dividing
cooling capacity, measured in British Thermal Units per hour (Btuh),
by the watts of power.
Energy factor
The fraction of water heater input
remaining in an assumed 64 gallons of hot water used by
residents.
Energy-recovery ventilator
A ventilator that recovers latent
and sensible energy from the exhaust airstream and imparts it to
the incoming airstream.
Envelope
The building shell. The
exterior walls, floor; and roof assembly of a building.
Environmentally sensitive
A person who is highly sensitive
to pollutants, often because of overexposure, is said to be
environmentally sensitive.
Evaporation
The change that occurs when a
liquid becomes a gas. Evaporation is the key process in
the operation of air conditioners and evaporative coolers.
Evaporator
The heat transfer coil of an air
conditioner or heat pump that cools the surrounding air as the
refrigerant inside the coil evaporates and absorbs heat.
Exfiltration
Air flowing out of a residence
from its conditioned space through the shell.
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F
Fiberglass
A fibrous material made by
spinning molten glass.
Fire stop
Framing member designed to stop
the spread of fire within a wall cavity.
Flue
A channel within an appliance or
chimney for combustion gases.
Foamboard
Plastic foam insulation
manufactured most commonly in 4'x8' sheets in thickness of 1/4"
to 3".
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H
Heat gains
Heat that accumulates in homes;
this is desirable during the heating season and undesirable
during the cooling season.
Heat loss
The amount of heat escaping
through the building shell during some period of time like a
month or a year.
Heat-recovery ventilator
A central ventilator that transfer
heat from exhaust to intake air.
Heating load
The maximum heating rate needed by
a building during the very coldest weather.
Heating seasonal performance
factor (HSPF)
Rating for heat pumps describing
how many Btus they provide per watt-hour of electricity
consumed.
House pressure
The difference in pressure between
the indoors and outdoors measured by a manometer.
Humidistat
An Automatic control that switches
a fan, humidifier, or dehumidifier on and off to control
relative humidity.
Hydronic
A heating system using hot water
or steam as the heat-transfer fluid.
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I
Incandescent lamp
The common light bulb found in
residential lamps and light fixtures and sold in stores
everywhere.
Infiltration
The inflow of outdoor air into the
indoors, which is accompanied by an equal outflow of air from
indoors to the outdoors.
Insulated glass
Two or more glass panes spaced
apart and sealed in a factory.
Insulation
A material that is designed to
slow down the flow of heat in or out of a house.
Internal gains
The heat generated by bathing,
cooking, and operating appliances, that must be removed during
the summer to promote comfort.
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K
Kilowatt (kW)
A unit of electric power equal to
1000 joules per second or 3412 Btus per hour.
Kilowatt-hour (kWh)
A unit of electric energy equal to
3600 kilojoules or 3412 btus.
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L
Latent heat
The heat absorbed or released by a
substance when it changes state. for instance, from a
liquid to a gas.
Low-e
Short for low emissivity, which
means the characteristic of a metallic glass coating to resist
the flow of radiant heat.
M
Make-up air
Air supplied to a space to replace
exhausted air.
Mastic
A thick creamy substance used to
seal seams and cracks in building materials.
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O
Open-combustion heater
A heater that takes its combustion
air from the surrounding room.
P
Pascal
A unit of measurement of air
pressure.
Payback period
The number of years that an
investment in energy conservation will take to repay its cost in
energy savings.
Perm
A measurement of how much water
vapor a material will let pass through it per unit of time.
Plate
A piece of lumber installed
horizontally to which the vertical studs in a wall frame are
attached.
Plenum
The piece of ductwork that
connects the air handler to the main supply duct.
Polyethylene
Polymer plastic used for vapor
barriers, air barriers, and foam backer rod.
Pressure
A force encouraging flow by virtue
of a difference in some condition between two areas.
Pressure boundary
An air barrier - usually the
primary air barrier.
Pressure diagnostics
The practice of measuring air
pressures and flows in buildings.
Pressure pan
A device used to block a duct
register, while measuring the static pressure behind it, during
a blower door test.
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R
R-value
A measurement of thermal
resistance.
Radiant barrier
A foil sheet or coating designed
to reflect heat rays or retard their emission.
Radiant temperature
The average temperature of objects
in a home like walls, ceiling, floor, furniture, and other
objects.
Radiation
Heat energy, which originates on a
hot body like the sun, and travels from place to place through
the air.
Radon
A radioactive gas that decomposes
into radioactive particles.
Recovery efficiency
A water heater's efficiency at
actually heating incoming water.
Refrigerant
A special fluid used in air
conditioners and heat pumps that heats air when it condenses and
cools air when it evaporates.
Register
A grille covering a duct outlet.
Relative humidity
The percent of moisture absorbed
in the air compared to the maximum amount possible. Air
that is saturated has 100% relative humidity.
Resistance
The property of a material
resisting the flow of electrical energy or heat energy.
Retrofit
An energy conservation measure
that is applied to an existing building. Also means the
action of improving the thermal performance or maintenance of a
building.
Return air
Air circulating back to the
furnace from the house, to be heated by the furnace and supplied
to the rooms.
Rim joist
The outermost joist around the
perimeter of the floor framing.
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S
Savings-to-investment ratio (SIR)
Measures how many times an energy
retrofit pays itself during its lifetime.
Sealed-combustion heater
A heater that draws combustion air
from outdoors and has a sealed exhaust system.
Seasonal energy efficiency ratio
(SEER)
A measurement of energy efficiency
for central air conditioners. The SEER is computer by
dividing cooling capacity, measured in Btuh, by the watts.
Sensible heat
The heat absorbed by a substance
which raises its temperature.
Sheathing
A structural sheeting, attached on
top of the framing, underneath siding and roofing of a building.
Shell
The building's exterior envelope -
walls, floor, and roof of a building.
Soffit
The underside of a roof overhang
or a small lowered ceiling, as above cabinets or a bathtub.
Solar gain
Heat from the sun that is absorbed
by a building and contributes to the need for cooling.
Solar heat
Radiant energy from the sun with
wavelengths between 0.7 and 1 micrmeters.
Solar heat-gain coefficient (SHGC)
The ratio of solar heat gain
through a window to incident solar heat. Includes both
transmitted heat and absorbed and reradiated heat.
Spillage
Temporary flow of combustion gases
from a dilution device.
Split-system air conditioner
An air conditioner that has the
condense and compressor outdoors and the evaporator indoors.
Supply air
Air that has been heated or cooled
and is then moved through the ducts and out the supply registers
of a home.
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T
Therm
A unit of energy equaling 100,000
Btus or 29.3 kilowatt-hours. Ten therms equal one
decatherm (dkt).
Thermal break
A piece of relatively low
conducting material between two high conducting materials.
Thermal resistance
Same as R-value, expressing
ability to retard heat flow.
U
U-value
The amount of heat that will flow
through a square foot of building cross-section with multiple
slabs of materials, Also known as U-factor when applied to
windows.
Unconditioned space
An area within the building
envelope that is not intentionally heated or cooled.
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V
Vabor retarder
A material that retards the
passage of water vapor.
Ventilation
The movement of air through an
area for the purpose of removing moisture, air pollution, or
unwanted heat.
Venting
The removal of combustion gases by
a chimney or other type of combustion vent.
Visible transmittance
The percent of visible light
transmitted by a glass assembly.
Volt
The energy contained in each unit
of charge in joules per coulomb.
W
Watt
A unit of electrical power
equivalent to one joule per second or 3.4 Btuh.
Weatherization
The process of reducing energy
consumption and increasing comfort in buildings by improving
energy efficiency of the building.
Weatherstripping
Flexible gaskets, often mounted in
rigid metal strips, for limiting air leakage.
Window films
Plastic films, coated with a
metallized reflective surface, that are adhered to window glass
to reflect heat rays from the sun.
Worst-case depressurization test
A safety test, performed by
specific procedures, designed to asses the probability of
chimney backdrafting.
Z
Zone
A room or portion of a building
separated from other rooms by an air barrier - not usually an
effective air barrier.
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