Improve your insulation vocabulary with these
definitions of commonly used terms. To find a word and its
definition, just click on the first letter of the word below.
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: A filter system with characteristics that roughly match the
response characteristics of the human ear at low sound levels
(generally below <55 dB but often used to gauge levels to 85
: The process of drawing fluid or gas into a porous material, such
as a sponge soaking up water.
: Refers to the surface retention or adhesion of a very thin layer
of water molecules to the surfaces of a material (such as
insulation fibers) with which they are in contact. Also see
: A value assigned to a material that exhibits thermal transmission
by several modes of heat transfer resulting in property variation
with specimen thickness or surface emittance.
: A vapor retarder laminate of reinforced bleached white kraft/foil
Device to maintain a ventilation space between the insulation and
roof deck, assuring air flow from the eave/soffit vents to ridge
vent or other roof vents provided in attics and cathedral ceilings
(Owens Corning product is Raft-R-Mate).
: Vertical member that forms the perimeter of a floor system in
which the floor joists tie in. Also known as the rim joist.
Bottom Plate (Sole Plate)
: The lowest horizontal member of a wall which rests on the
sub-floor, to which the studding is nailed.
British Thermal Unit
: The heat required to raise the temperature of a pound of water
: The empty space between studs or joists typically filled with
: A thermometric scale in which the freezing point of water is 0°C and its boiling point 100°C at normal sea level atmospheric pressure (14.7 psi). °C = (°F-32)/1.8.
: A horizontal board connecting two opposite rafters at a level
considerably above the wall plate. Also known as collar tie.
: Changing a substance from a vapor to a liquid state by removing
the heat. The condensate shows up on surfaces as a film or drops of
: The time rate of steady state heat flow through a unit area of a material or construction induced by a unit temperature difference between the body surfaces.
C = Btu/hr·ft2·°F (W/m2·°C)
: The time rate of steady state heat flow through a unit area of homogeneous material induced by a unit temperature gradient perpendicular to that unit area.
k = Btu·in/hr·ft2·°F (l = W/mS°C)
Cooling Degree Day
: A unit, based on temperature difference and time, used in
estimating fuel consumption and specifying nominal cooling load of
a building in summer.
: An opening to allow the passage of air through the unfinished
area under a first floor. Ideally there should be at least two
vents per crawlspace.
: Small wood pieces placed at angles so that they extend from the
bottom of one floor joist to the top of the adjacent joist to add
stability to the structural members.
: The mass of a substance per unit of volume of that substance.
DN: Diameter, Nominal
: Metric equivalent of NPS (Nominal Pipe Size, inches).
: Vent openings located in the soffit under the eaves of a house to
allow the passage of air through the attic and out the roof
Economic Thickness (of
: That thickness which provides the lowest possible annual cost of
energy, insulation and energy producing equipment.
: The ratio of the radiant flux emitted by an ideal, perfect
emitter and absorber of thermal radiation at the same temperature
and under the same conditions.
Equivalent Thickness (of
: When r1 = the inner radius of a single layer of cylindrical
insulation and r2 = the outer radius, equivalent thickness = r2 1n
: Stapling facing flange to the front side of a stud or rafter,
along the 1½" dimension.
: Insulation with a facing already attached. Kraft paper or
foil-backed paper are common facings.
: A thermometric scale in which 32°F denotes freezing and 212°F the boiling point of water under normal sea level atmospheric pressure of 14.7 psi. °F = 1.8°C + 32.
Fiber Glass Insulation
: An energy-efficient glass fiber product manufactured by Owens
Corning to ensure the best thermal and noise control performance
: A ceiling with no change in elevation.
Foil-Faced Vapor Retarder
: Created by coating a foil-backed paper with a thin layer of
adhesive, then attaching it to the fiber glass.
: The number of cycles per second measured in units of Hertz.
: A vapor retarder laminate of foil/ scrim (reinforcement) kraft
construction. Also known as FSK.
: Flat pieces of lumber used to build out framing to an even
surface, either the leveling of a part of a wall or ceiling. In
block or concrete construction, they may be used as a means of
attaching the interior or exterior finish.
Gable End Walls
: The triangular end of an exterior wall above the eaves.
: A louver vent mounted in the top of the gable to allow the
passage of air through the attic.
: Glass in a strand form. The ingredients are essentially the same
that go into any glass product such as a window pane or drinking
: The rate at which heat moves from an area of higher temperature
to an area of lower temperature. Btu/hr (W/hr). Heat flow is
generally used to quantify the rate of total heat gain or heat loss
of a system.
: Marking on recessed lighting fixtures indicating that they are
designed for direct insulation contact.
Inch of Water (in.
: A unit of pressure equal to the pressure exerted by a column of water 1 inch (25mm) high at a temperature of 39.2°F (4°C).
: Stapling to the inside portion of the stud or rafter.
: Denser insulation products have more fibers per square inch and,
therefore, give you greater insulating power through higher
: 16" or 24" wire rods, nylon banding, or crisscrossed
wire to hold floor insulation in place.
: Horizontal framing member set from wall to wall to support the
floor or ceiling.
: Walls of varying length. Used to provide additional support to
roof rafters with a wide span or to finish off an attic.
Kraft-Faced Vapor Retarder
: Created by coating kraft paper with a thin layer of asphalt
adhesive. The coated side of the kraft paper is then applied to the
unfaced insulation material. The asphalt adhesive bonds the kraft
paper and the insulation together.
:The arithmetic mean between hot and cold surface temperatures of
an insulated pipe, duct or vessel. tm = (t1 + t2)/2.
: A metal channel through which hot air, gas, steam or smoke may
: Nominal Pipe Size, inches. Metric equivalent of DN (Diameter,
: The material will not burn. The glass fibers in PINK® fiber glass
insulation have a natural fire resistance, and are considered
non-combustible when tested in accordance to ASTM E136.
: A single number rating, the arithmetic average of the individual
sound absorption coefficients of a material at 250, 500, 1000 and
2000 Hz to the nearest .05.
: A range of frequency where the highest frequency of the band is
double the lowest frequency of the band. The band is usually
specified by the center frequency.
: The mass rate of water vapor flow through one square foot of a
material or construction of one grain per hour induced by a vapor
pressure gradient between two surfaces of one inch of mercury or in
units that equal that flow rate.
Polyethylene Vapor Barrier
: Plastic film used to prevent moisture from passing through
unfaced insulation. Both 4- and 6-mil polyethylene are preferred
because they are less likely to be damaged during construction.
: A slope framing member that supports a pitched roof.
: A measure of the amount of moisture in the air with respect to
the temperature. It is the ratio of the moisture present to the
maximum amount of moisture the air can hold at that
: Metal channels used to further inhibit sound transmission through
wall and ceiling framing. Create a break in the vibration path from
drywall to the framing.
: A vent mounted along the entire ridge line of the roof to allow
the passage of air through the attic or cathedral ceiling.
: A louver or small dome mounted near the ridge of the roof to
allow the passage of air through the attic.
: Measure of resistance to heat flow. Insulation materials have
tiny pockets of trapped air. These pockets resist the transfer of
heat through material. The ability of insulation to slow the
transfer of heat is measured in R-values. The higher the R-value,
the better the insulation material's ability to resist the flow
of heat through it.
: Self-sealing lap, a feature of pipe insulation covering in which
an adhesive strip provides mechanical and vapor retarder closure of
the longitudinal seam. See also SSL II.
: Pipe insulation jacket closure with a double adhesive,
self-sealing lap to close the longitudinal seam. (exclusive with
: Refers to the taking up and holding of water by various processes
such as absorption and adsorption.
: The process of dissipating or removing sound energy; the property
possessed by materials, objects and structures (such as rooms) of
absorbing sound energy; the measure of the magnitude of the
absorptive property of a material, object or structure.
: The percentage of sound energy incident on the surface of a
material that is absorbed by the material.
: A protruding edge on faced insulation used to staple the
insulation to the framing.
: The normal force per unit area at a small hole in the wall of a
duct through which a fluid is flowing.
: A vertical framing member used in both exterior and interior
: The structural material that spans across floor joists. It serves
as a working platform during construction and provides a base for
the finish floor.
: The horizontal member nailed to the top of the studding of a
: Insulation with no attached facing.
: Helps control the amount of moisture passing through the
insulation and collecting inside exterior walls, ceilings and
: Creates a positive flow of air that allows the house to
"breathe" and helps prevent moisture build-up
: In wood-frame construction, the wall is composed of both vertical
and horizontal wood members. The vertical members are usually
called studs, while the horizontal members are usually called
plates. A bottom plate is at the bottom of the wall frame assembly,
while two plates are usually used at the top (double top
: In heating climates, it is the interior side of an exterior wall
: Time rate of water vapor transmission through unit area of flat
material or construction, induced by vapor pressure difference
between two specific surfaces, under specified temperature and
Water Vapor Retarder
: A material or system that adequately impedes the transmission of
water vapor under specified conditions.
References: NEBB, National Environmental Balancing
Bureau: Environmental Systems Technology, Chapter 19, Glossary.
ASTM, American Society for Testing and Materials: ASTM C 168-90,
Standard Terminology Relating to Thermal Insulating Materials.