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Terminology

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A-C

TERM

MEANING

adjustment clip hardware on hung window jambs to align jamb
after window installation.
AIF. Acoustic Insulation Factor, a sound
transmission measure used in Canada
air infiltration the amount of air leaking in and out of a
building through cracks in walls, windows, and doors (the lower, the better).
ambient temperature The outdoor temperature.
anodize the process that provides a hard, durable
oxide film on the surface of aluminum, by electrolytic action.
apron Interior flat trim piece which is used under
the stool at the bottom of the window.
argon An inert, colorless, and harmless gas used
instead of air in sealed spaces between panes of glass in insulating glass units to
increase insulation. Argon is less conductive to heat than air.
ASHRAE American Society of Heating,
Air-conditioning and Refrigeration Engineers.
astragal The center member of a double door, which is
attached to the fixed or inactive door panel.
awning A type of window with a top-hinged sash that
swings out at the bottom — lets in fresh air while keeping rain out.
awning window A window unit in which the bottom of the
sash swings outward.
back bedding The process of adhering and sealing.
balance a mechanical device, normally spring loaded,
used in hung windows to counterbalance the weight of the sash during opening and closing.
balance shoe nylon hardware in hung window jamb that
connects the balance with the sash.
bay window A composite of three windows, usually made
up of a large center unit and two flanking units at 30- or 45-degree angles to the wall. A
bay projects from the wall of the structure.
bead a molding or stop placed around a window
frame to hold the glass in place by pressure.
billet the cylindrical form of aluminum just prior
to the extruding process.
bite a glazing term referring to the dimension of
the glazing leg which overlaps the edge of the glass.
bow window A composite of four or more window units in
a radial or bow formation gently curved contour. Bow windows also project from the walls
of the structure.
brickmold A type of external casing which frames
windows and doors. Exterior casing around window to cover jambs and provide means for
nailing during installation.
BTU British Thermal Unit — a basic measurement
of heat. One BTU equals the amount of heat needed to raise one pound of water 1 degree
Fahrenheit. (A match contains approximately one BTUs, and a well-insulated house in the
Ottawa region may require 90 million BTU for space heating over the year). The metric
equivalent is 1054.35 Joule.
casement A type of window with a side-hinged sash
that opens like a door — the best window for catching breezes and providing
cross-ventilation.
casement window A window unit in which the single sash
cranks outward, to the right or left. Projecting window hinged at the sides and usually
opening outward like a door.
casing Molding of various widths, thickness and
shapes applied to the framework of window and door units. Interior casing is a flat,
decorative moulding which covers the inside edge of the jambs and the rough opening
between the window unit and the wall. Exterior casing (or brick mould) serves the same
purpose, while it also is an installation device through which nails are driven to install
the window unit into the wall.
caulking Sealants used to seal fixed and movable
construction joints and prevent infiltration.
center of glass All glass area of a window except that
within 2.5″ (10cm) from the edge of the glass — used in measuring and calculating
glazing performance such as R-values and U-values.
cfm cubic feet per minute – a unit of
measure used in air infiltration testing, e.g., “maximum .10 cfm per foot of sash
perimeter.”
check rail On a double-hung window, the bottom rail of
the upper sash and the upper rail of the lower sash, where the lock is mounted. The top
rail of the lower sash and the bottom rail of the upper sash which meet when a double-hung
window is closed. Both pieces should be weather stripped for maximum weatherability.
circlehead A generic term referring to any of a variety
of window units with one or more curved frame members, often used over another window or
door opening.
cladding An aluminum material locked to the outside
faces of many Pella products to provide a durable, low-maintenance exterior surface.
clerestory A window placed vertically in a wall above
one “s line of vision to provide natural light — often at the intersection of two
offset roof planes.
clerestory window A venting or fixed window above other
windows or doors on an upper outside wall of a room.
CMR Centerline of Meeting Rail – a
reference line used to locate integral mullions and/or size oriel (unequal) sash, e.g.,
“the height of the lower sash shall be 22″ from the frame sill to CMR.”
collection The act of trapping solar radiation and
converting it to heat.
comfort engineering Optimizing glazing selections on a
window-by-window basis to fulfill a prioritized set of objectives — e.g., comfort, energy
efficiency (both summer and winter), UV protection, natural lighting, desired aesthetics,
views, and budget. Willmar Windows” sales consultants act as expert comfort
engineers, finding appropriate solutions for individual needs.
condensation The change of a gas to a liquid state.
Because warm air can hold more water vapor than cold air, as warm air cools its ability to
hold water vapor is reduced. Excess moisture condenses on the warm side of glass. e.g.,
condensation on the outside of a glass of ice-water.
conduction A process of heat transfer whereby heat
moves directly through a material by molecular agitation.The handle of a cast-iron frying
pan becomes hot due to conduction.
conductivity The transfer of heat through a given
material — see U-value which is the measure of conductivity, the inverse of R-value.
convection A process of heat transfer whereby heat
energy is transferred from one location to another — created by the motion of air
resulting from a difference in temperature and the action of gravity.
cottage double-hung A double-hung window in which the upper sash
is shorter than the lower sash.
crack length total outside perimeter of window sash/vent;
used when defining the AAMA air infiltration rate.
CRF Condensation Resistance Factor – an
indication of a window”s ability to resist condensation (the higher the better).
curb appeal The visual attractiveness of a home as seen
from the street — often the first impression. Realtors see curb appeal as an influential
factor in evaluating and selling homes.
custodial lock window hardware only operable with a tool or
key.

D-F

 

TERM

MEANING

daylight transmittance The percentage of visible light that glazing
transmits through a window — a standard clear dualpane has a daylight transmittance of
82%.
debridge the process of cutting away the metal on the
bottom of an aluminum thermal break cavity once the two-part polyurethane has reached full
strength, thus creating a thermally broken extrusion.
desiccant a porous crystalline substance used to
absorb moisture and/or sealant solvents from within the sealed air space of an insulating
glass unit.
design load the project wind load to be determined by
the architect and expressed in psf, e.g., “the project design load shall be 38.7 psf,
both positive and negative.”
designation number prescribed by AAMA. One for each window
style. It provides a code for architectural selection, e.g., TR-5000 = DH-C45 = Double
Hung – Commercial Grade – 45 psf Design Pressure.
dessicant Crystalline substance used to absorb
moisture from air within IGUs.
dew point The temperature at which water vapor will
condense as warm, moist air is cooled.
die a perforated steel block through which
aluminum or vinyl is extruded.
direct gain A direct gain passive solar system utilizes
south-facing windows to open a house to the sun. A large window area accepts direct
sunlight while thermal mass serves as storage.
dormer A space which protrudes from the roof of a
house, usually including one or more windows.
double glazing Use of two panes of glass in a window to
increase energy efficiency and provide other performance benefits.
double glazing panel (dgp) A removable interior glass panel which
creates an air space between the exterior glazing and itself. It provides improved
insulation and condensation control and allows for between-glass shading options such as
muntins, blinds and pleated shades.
double strength glass (DSB) 1/8″ thickness.
double-hung window A window unit that has two operable sashes
which move vertically in the frame. Two vertically sliding sash which by-pass each other
in a single frame. Sashes typically fit within vinyl balances and tilt out and remove for
safe, easy cleaning.
drip cap A molding placed on the top of the head
brickmold or casing of a window frame.
dry glazing a method of securing glass in a window frame
with a dry, preformed, resilient gasket, without the use of a glazing compound.
dual durometer A material that has two or more levels of
flexibility. An example is the weatherstripping used between the frame and sash of a Pella
casement window.
dual durometer bead a vinyl glazing bead with a softer flap
against glass and a harder section inserted into sash member.
dual glazed two single lites glazed into a split sash
with an airspace, not hermetically sealed, between the two single lites.
dual window two windows joined together, one in front of
the other, to provide superior sound control.
dualpane Two panes of glass with a single airspace,
held together by an edge spacer — the most economical IGU.
edge of
glass
The glass area within 2 1/2″ (10cm) of
the edge of a window.
egress window a window with specific release hardware and
minimum clear opening size to allow occupants to escape through the window in case of a
fire.
electrostatic a painting process by which the aluminum is
grounded and the paint carries a positive electric current. This creates a magnetic
attraction between the paint and the aluminum allowing for uniform paint coverage on all
exposed extrusion surfaces.
emissivity Emission, or the ability to radiate heat in
the form of long-wave radiation.
end dam used to close the ends of a subsill so the
water will not leak out the ends. It makes the subsill a complete water trough allowing it
to collect excess water and drain it to the exterior.
EPDM Ethylene Propylene Diene Monomer – a
weather resistant synthetic rubber from which many flexible gaskets for windows are made.
EPDM Ethylene Propylene Diene Monomer – a
weather resistant synthetic rubber from which many flexible gaskets for windows are made.
ER Rating Energy Rating number developed by CSA
(Canadian Standards Association) to compare the thermal performance of windows. Measured
in watts per square meter (W/m2).
escutcheon plate hardware for handles etc.
expansion mullion self mulling window frame jambs that, when
slipped together, permit expansion/contraction while preserving strength and
watertightness.
extension jambs Flat wood parts which are nailed to the
interior edges of the window jamb to extend it in width and adapt to a thicker wall. The
inside edge of extension jambs should be flush with the finished wall surface. Interior
casing is then nailed into it.
exterior glazed glass glazed from the exterior of the
building.
extrude the process of shaping aluminum or vinyl by
forcing it through a die.
extrusion the finished form after pushing aluminum or
vinyl through the die.
extrusion A form produced by forcing material through
a die. Pella window frames are clad with extruded aluminum.
fenestration An architectural term referring to the
arrangement of windows in a wall. From the Latin word, “fenestra,” meaning
window.
fenestration The arrangement of windows in a building.
fin seal a form of pile weatherstrip that has a
plastic mylar fin centered in the pile. This fin reduces air infiltration and ensures
weatherstrip contact throughout the window’s life.
finger-jointing A means of joining individual pieces of wood
together to form longer lengths. The ends of the pieces are machined to form a set of
interlocking fingers, which are then coated with adhesive and meshed together under
pressure.
fixed Non-venting or non-operable.
fixed unit A stationary window or door that does not
open — also referred to as a fixed sash.
flange frame a window frame with the head, jamb, and sill
exterior perimeter leg longer than the interior perimeter leg.
flashing A thin strip of metal or synthetic material
that diverts water away from a window or skylight. A metal or plastic strip attached to
the outside of the side jambs and head to provide a weather barrier, preventing leakage
between the window frame and wall.
float glass transparent glass with flat, parallel
surfaces formed on the surface of a pool of molten tin.
foam spacer Foam material placed in the airspace of the
insulating glass windows to enhance the appearance and improve the performance of the
window.
frame The enclosure in which window sash or door
panels are mounted. Outside members of a window unit which enclose the sashes. Composed of
side jambs, head jamb and sill.
frame Consists of a head, jambs, and sill to form
an opening into which sash or door panels fit.
French hinged door Hinged door(s) which have wider panel
members around the glass.
French sliding door A sliding door which has wider panel members
around the glass, giving the appearance of a French hinged door.

G-I

 

TERM

MEANING

gasket a rubber or plastic pliable material used to
separate glazed glass and aluminum or vinyl.
glazing Glass in a window or door; the act or
process of fitting glass or panels into the sash or frame of the window.
glazing The installation of glass into a window or
door sash. Also refers to the type of glass used in the process.
glazing bead a molding or stop around a window frame to
hold the glass in place by pressure. A vinyl or wood strip, applied around the perimeter
of the glass on the exterior of the window sash, for holding the glass in place.
glazing stop The part of the sash or door panel which
holds the glass in place.
greenhouse effect The property of glass that permits the
transmission of short-wave solar radiation, but is opaque to long-wave thermal radiation.
The interior of a car heating up in direct sun illustrates the greenhouse effect.
grille A term referring to windowpane dividers or
muntins, usually a type of assembly which may be detached for cleaning.
grilles Decorative inserts for windows or door
glazing that add a traditional touch — available as fixed or removable inserts, in wood,
brass, or vinyl.
grilles-between-the glass Aluminum bars in varying thicknesses and
profiles sealed between insulating glass panels to simulate muntin bars.
gusset a concealed, strong, right-angled shape used
to reinforce mitered corners in tubular aluminum extrusions
head The main horizontal member forming the top
of the window or door frame.
head board A flat board, cut to fit the contour of a
Bow or Bay window, for installing between the head jambs and the flat wall surface to
finish off the area which would normally be ceiling.
head expander a u-shaped extrusion slipped over the frame
head that, when pushed up, closes the gap above the window after window installation.
header A horizontal framing member placed over the
rough opening of a window to prevent the weight of wall or roof from resting on the window
frame. A beam across the top of the rough opening for a window or door. Headers rest on
jack studs and support the weight of the wall above the window unit. They are often
constructed out of doubled 2×6’s, 2×10’s or 2×12’s.
heat fusion (welding) method to join PVC frame and/or
sash members by heating the cut ends, squeezing them together, and allowing the assembly
to cool.
heat treating the process where glass or aluminum
extrusions are heated and cooled to make these materials harder and stronger.
hermetically sealed unit an insulating glass unit that is sealed
against moisture. The unit is made up of two lites of glass, separated by a roll-formed
metal spacer tube (at the full perimeter) which contains a moisture and/or solvent
absorbing material. The unit is then completely sealed, creating a moisture free air
space.
hollow extrusion an extrusion having an enclosed cavity
within it.
hopper A window unit in which the top of the sash
swings inward.
IGCC Insulating Glass Certification Council
– directs a certification program of periodic accelerated laboratory testing and
unannounced plant inspections to ensure sealed insulating glass performance is in
conformance with ASTM E 774-88.
inside snap trim used in retrofit work to cover the inside
gap between the new window and the existing opening.
insolation Incident solar radiation — the total
radiation striking an exposed surface.
Insulating Glass Unit (IGU) A combination of two or more panes of glass
with sealed air space(s) between panes — dualpanes, tripanes, and quadpanes. Also
referred to as thermopanes or sealed units.
Insulating glass(IG) two pieces of glass spaced apart and
hermetically sealed to form a unit with an air space between. Heat transmission through
this type of glass may be as low as half that without such an air space. A combination of
two or more panes of glass with a hermetically sealed air space between the panes of
glass. This space may or may not be filled with an inert gas, such as argon. Two sheets of
glass bonded together in a unit to enclose a captive air space. Units are constructed with
a metal spacer inside the outer perimeter. The outer edges are sealed. Spacers contain
desiccant material for absorbing and holding any remaining moisture in the air space.
insulation A material with high resistance (high
R-value or low U-value) that is used to retard heat flow. Air, Argon, or Krypton gas
spaces between panes of glass provide insulation in IGUs.
integral mullion a frame member trapped within the master
frame to separate vents or fixed glass.
interior glazed glass glazed from the interior of the
building.
interlock a design feature which enables sash to
become engaged with one another when closed
internal gain The heat produced in the interior of a
dwelling from the operation of lights, appliances, etc.

J-L

 

TERM

MEANING

jack stud Vertical framing members, generally
2×4’s, which form the inside of the window or door rough opening. They support the
header and run down to the sole plate.
jamb The main vertical members forming the sides
of a window or door frame. Side jambs are the vertical pieces of a window frame. The head
jamb is the horizontal piece across the top. The vertical member of a window frame.
jamb liner In a modern double-hung window, the track
installed inside the jambs on which the window sashes slide. Vinyl or metal covering
applied to the side jambs of double hung and single hung windows. They are generally
formed to include an integral balance system and stops for the exterior and interior
surfaces of the sash.
K.D. Knocked Down – product components
that are shipped unassembled, e.g., the frame for a sliding glass door.
keeper a hardware device into which a window
locking latch engages for security. The receiving portion of a lock that interlocks with
the lock arm. It’s mounted to the upper sash check rail on a double hung or single
hung window and the inside surface of the sash stile on a casement window.
kitchen bay A small bay window used above counter-height
in kitchens — allows for a wider view and an inside sill for herbs and flowers.
knocked down (kd) Unassembled window or door unit.
krypton An inert, colorless gas used instead of air
in sealed spaces between panes of glass in insulating glass units to increase insulation.
Provides greater insulation than Argon.
laminated glass two or more lites of glass bonded together
with a plastic inner layer.
laminated glass A type of safety glass comprised of two
pieces of glass with a clear vinyl interlay. .
left or right location information, always outside looking
in, that can be used to specify direction, e.g., “the operating sash slides to the
right.”
lift A handle or grip installed or routed into
the bottom rail of the lower sash of a double hung or single hung window
light A separately framed piece of glass in a
window or door. A traditional double-hung window, for instance, often has several lights
divided by muntins in each sash. Such windows are described as six-over-six,
eight-over-one, twelve-over-twelve, etc., to indicate the number of lights in each sash.
Sometimes spelled ‘lite.’ A single (monolithic) glass pane or piece.
low e or low-emissivity
(low-e) glass
a transparent coating applied to a glass
surface to separate long wave (heat) energy and short wave (light) energy. The long wave
is reflected back to the heat source. The short wave is allowed to pass through the
coating. A special type of glass having a transparent material fused into its surface
which acts as a thermal mirror.
low e glass Low Emissivity glass with a transparent
coating which acts as a thermal mirror — used to increase a window’s insulating value,
block or increase heat flow, and reduce fading. See Solar Gain and Solar Shield.

M-O

 

TERM

MEANING

marine glazing a u-channel of soft PVC which is
wrapped around the edge of the glass, cushioning the glass against the aluminum or vinyl.
This process allows for unrestricted expansion and contraction and watertightness
masonry opening The space in a masonry wall left
open for windows or door. The opening in a masonry wall to accept a window or door unit,
the same as a rough opening in a frame wall. The header (or lintel) in a masonry opening
is usually a steel beam.
meeting rail the part of a hung window where
the two sash meet and create a weather barrier.
mill finish the original finish produced on
aluminum by extruding.
mortise A slot or rectangular cavity cut
into a piece of wood to receive another part.
mortise-and-tenon
A strong wood joint made by
fitting together a mortise in one board and a matching projecting member (tenon) in the
other.
mullion an extrusion that joins windows.
A wood or metal part used to structurally join two window or door units. The vertical or
horizontal divisions or joints between individual windows in a multiple window unit.
mullion Applies to any short or light
bar, either vertical or horizontal, used to separate glass in a sash into multiple lights.
Also called a windowpane divider or a grille.
mullion cover an extrusion that joins panning
perimeter legs that extend over existing mullions.
muntin extrusions in the sash which are
exterior (outside of the glass exterior face), internal (in the insulating glass
airspace), or true (dividing the glass) which appear to or actually divide the glass into
smaller lites
nailing
fin
A vinyl or metal flange
integrated into (or attached to) the perimeter of a window frame for installation onto the
rough opening’s header, jack studs and rough sill. A continuous nailing fin may
surround the frame as with an all-vinyl window or a nailing fin may be affixed to the head
and side jambs as with a vinyl clad window frame.
neoprene a synthetic rubber having
physical properties closely resembling those of natural rubber. It has extremely good
weather and temperature resistance, both heat and cold, with ultraviolet stability.
nite latch hardware which, when extended,
restricts the sash opening to a predetermined dimension.
obscure
glass
mainly used for decoration,
diffusion, or privacy. The pattern is rolled into the hot glass during glass
manufacturing.
operating unit A window or door that opens —
also referred to as a vent unit or operator.
operator A metal arm and gear device
which allows for easy opening and closing of projecting windows; e.g. casement and awning
windows.
oriel window a window with unequal sash.
orientation The compass direction that a
structure faces. To optimize heat-gain, the major facade of a building should face South
(a variation as much as 30 degrees east or west of south will not seriously affect
performance).

P-R

 

TERM

MEANING

palladian window A large, arch-top window flanked by smaller
windows on each side.
pane A framed sheet of glass.
panel Usually refers to the separate panel or
panels in a door frame.
panel Either an opaque glazing material or the
operating portion of a sliding glass door.
panning a set of extrusions which are fastened to a
new window to cover the exterior perimeter of an existing opening in a retrofit
application
parting stop In a double-hung window, a strip of wood
applied to the jamb to separate the sash.
passive solar A solar heating system which operates on
natural thermal processes, and that uses no external mechanical power to move the
collected heat. Generally, the building’s structure itself forms the solar system.
patio doors Sliding glass doors, often used for access
to a deck or terrace.
picture frame casing The use of casing on all four sides of the
interior of a window. The stool and apron at the sill are replaced with casing.
picture window A large stationary (non-ventilating) window
which is designed for a maximum view without obstruction.
picture windows A type of window using only fixed units —
best for a clear view and energy efficiency.
pleated shade A shade of folded fabric which can be
installed like regular shades or between the panes of glass of a window.
prime frame a window frame which has an extended
perimeter leg 1″ back from the window exterior plane, which becomes a nailing fin for
new construction installation.
psf pounds per square foot – a
measurement of air pressure used in window testing, e.g., 1.56 psf (25 mph) or 6.24 psf
(50 mph).
PVC Poly Vinyl Chloride – in rigid
frame/sash members, and in flexible gaskets.
pyrolytic coating A special coating “sprayed”
directly onto glass while it is still in a molten state, resulting in a permanently
embedded surface coating.
r value a measurement of heat resistance (the
higher, the better). R value = the number 1 divided by the U value. Resistance to thermal
transfer or heat flow. Higher R-value numbers indicate greater insulating value.
radiation The direct process of heat transfer through
space by means of electromagnetic waves. Energy in the form of rays of light is
transferred from body to body without heating the intermediate air.
rail The top and bottom horizontal members of the
framework of a window sash or door panel. a horizontal sash member.
receptor framing system consisting of two
snap-together extrusions used to contain a window frame head and jambs in a masonry type
opening. It allows for deflection and inconsistencies in the openings.
reflectance back. A measurement in percentage of the visible
light reflected back into a room. For ease of seeing to the outside, a lower rating is
better
reflected radiation Solar radiation that strikes an exposed
surface (like a window) after being reflected from the ground, trees, buildings, snow,
etc. Reflected radiation can provide a significant amount of heat when vertical windows
are used.
reflective glass glass with metallic coatings applied onto or
into the glass surface to reduce solar radiant energy and visible light transmission
relative heat gain A measurement of the total heat gain through
glazing for a specific set of conditions.
relative humidity Humidity expressed as a percentage of the
maximum possible humidity at a given temperature.
removable grilles Ornamental or simulated muntins and bars
designed to provide a divided light appearance. Generally made of wood, they are applied
to the inside of the sash against the glass surface for easy removal.
rough opening The opening built into a frame wall to
receive a window or door unit. It is formed with a header along the top that’s
supported by jack studs on each side. The rough sill at the bottom is supported by
cripples. A rough opening is generally greater in width and height than the window or door
unit. The framed opening in a wall into which a window or door unit is to be installed.
rough sill The horizontal framing piece, usually a 2×4,
which forms the bottom of the rough opening. It is toe-nailed into the jack studs and
supported by cripples.

S-U

 

TERM

MEANING

sash The inner frame which holds glass in
operable and fixed window units.
sash the operating portion of a hung or
horizontal sliding window. A single assembly of stiles and rails made into a frame
for holding glass. The framework holding the glass in a window unit. It’s composed of
two stiles (sides) and two rails (top and bottom).
sash balance A coiled spring or spiral system integrated
into the jamb liners to allow double hung or single hung sashes to open and close. They
also allow the sashes to remain open in varied positions..
sash cord In double-hung windows, the rope or chain
which attaches the sash to the counter balance.
sash lift A protruding handle screwed to the inside
bottom rail of the lower sash on a double-hung window. Available on all Pella double-hung
windows.
sash lock Generally, a cam-action lock applied to the
check rails of a double/single hung window, or sliding window to pull the check rails
tightly together. They are also applied to the open edges of a projecting window to seal
the sash tightly to the frame. Sash locks provide security and weatherability.
sash stop cover in jamb track that reduces sash travel
on hung windows.
sash weights In older double-hung windows, the concealed
cast-iron weights which are used to counterbalance the sash.
screw boss a continuous screw track in an extrusion.
The track is designed to accept a specific diameter sheet metal screw to provide a secure
means of fastening extrusions without the use of reinforcement.
sealed unit See Insulating Glass Unit.
SEAT BOARD A flat board cut to fit the contour of a bow
or bay window that’s installed between the sills and the flat wall surface. They
provide a seat or shelf space.
SGCC Safety Glazing Certification Council
– administers tempered glass testing and certification program.
shading coefficient The measure of how well glazing blocks solar
heat gain relative to 1/8″ clear glass under the same conditions. The lower the
shading coefficient, the better the unit blocks solar heat.
shims Wood wedges used to secure the window or
door unit in the rough or masonry opening in a square, level and plumb position during and
after installation.
side lights Tall, narrow, fixed or operating sash on
either or both sides of a door to light an entryway or vestibule. Narrow fixed units
mulled or joined to door units to give a more open appearance. Tall, narrow, fixed or
operating sash on either or both sides of a door to light an entryway or vestibule.
sidelight A narrow fixed unit joined to one or more
doors, providing a more open appearance.
sill The bottom of a door or window frame.
sill The main horizontal member forming the
bottom of the frame of a window or door. The horizontal piece that forms the bottom of a
window frame. It is generally slanted down to the outside to shed standing water. The
lower horizontal member of a window frame.
sill angle extrusion that, when applied below the
window, permits the gap below the window to be closed after window installation.
sill course The row of bricks, cement blocks or stones
laid horizontally at the bottom of a masonry opening.
simulated divided light A method of constructing windows in which
muntins are affixed to the inside and outside of a panel of insulating glass to simulate
the look of true divided light.
single glazing Use of single panes of glass in a window.
Not as energy-efficient as double glazing.
single strength glass (SSB) 3/32″ thickness.
single-hung A double-hung type of window in which the
top sash is fixed or inoperable
skylight A special window set into a roof to provide
natural light.
slider A type of window with one fixed sash, and
one that slides sideways — good where outside clearance is limited.
sliding window A window with two or more sashes that slide
horizontally past each other within the frame.
solar gain The absorption of heat from the sun — the
amount of solar radiation (measured in BTUs) received by a surface. Glazing with Solar
Gain Low E coatings optimize the collection of the sun’s heat, and should be used when
heat gain is desired.
solar heat gain coefficient The fraction of incident solar radiation
entering a home through the windows — the lower the number, the better the window is at
blocking heat gain. See Solar Shield.
solar shield The shielding or blockage of the sun’s heat.
Willmar’s Solar Shield Low E coatings provide solar shading, blocking heat gain from the
sun. Glazing with Solar Shield coatings should be used when there is potential for
excessive heat gain, or when heat gain is undesirable.
solar tempered house A dwelling that obtains a large part of its
heat from the sun.
solar transmittance The percentage of total solar energy that
glazing transmits through a window — a standard clear dualpane has a solar transmittance
of 71%.
sole plate The bottom horizontal piece in a frame wall,
usually single or double 2×4’s. The wall is nailed into the deck or rough floor
through the sole plate.
solid extrusion an extruded shape other than a hollow or a
semi-hollow extruded shape. Less costly to produce compared to semi or hollow shapes.
Sound Transmission Class
(STC)
A rating measure for the ability of glazing
to block out sound from outside sources. The higher the STC rating the better the sound
blockage (and the quieter the home).
spandrel glass glass mounted between floors of a building.
It is usually made opaque to hide building components.
specialty A type of window with distinct shapes, such
as octagons, round-tops, ellipticals, rakeheads — virtually any shape can be custom
manufactured.
sputtered coating A coating deposited on glass or film
atom-by-atom in a precise process inside a vacuum chamber.
STC Sound Transmission Class – describes
acoustical control for interior panels, and, even though inadequate, is currently the only
criteria for exterior windows. The higher the number, the better the product is at
resisting typical sound frequencies excluding airplane and train noises.
stile a vertical sash member. The vertical side
pieces of a window sash or door panel. The main vertical members of the framework of a
sash or door panel.
stool An interior trim piece on a window which
extends the sill and acts as a narrow shelf. The interior horizontal trim piece at the
bottom of the window frame. The shelf-like piece that projects into the room.
stop A molding used to hold, position or separate
window parts.
subsill refers to extrusions positioned to collect
water leakage through mullions and products and drain it to the exterior. Used where high
performance water resistance is required and for windows joined with mullions. It runs
continuously across the opening width and can be spliced together to cover wide openings.
The ends are sealed with end dams.
sun Our day star and the source of life and
energy on earth, located 93 million miles away, with an expected life of 5 billion years.
A tremendous source of “free” energy if harnessed intelligently.
tempered
glass
Glass that has been heat-treated to become
more than three times stronger — also known as safety glass because it breaks into small
pebbles rather than jagged shards. It is used in sliding glass doors and windows
susceptible to impact or breakage.
tempered glass Glass manufactured to withstand greater than
normal forces on its surface. When it breaks, it shatters into small pieces to reduce
hazard. Glass that has first been cut to size, then heated to a very high temperature and
then rapidly brought back to room temperature. It will withstand severe punishment from a
blunt object; however, any pointed object will break the glass instantly and the glass
will crumble into many, very small pieces.
tenon A rectangular projection cut out of a piece
of wood for insertion into a mortise.
thermal break An air space or insulating material which
prevents the direct coupling of a cold surface to a heated surface.
thermal break an element of low conductivity
(polyurethane) placed between elements of higher conductivity (aluminum) to reduce the
flow of heat and cold.
thermal break The addition of a thermal insulating
material between two thermally conductive materials.
thermal bridge The direct coupling of a cold surface to a
heated surface, allowing heat transfer via conduction.
thermal mass the amount of heat storage capacity
available in a given material or assembly. Thermal mass in a home (tile floors, stone
fireplace, etc.) will absorb excess heat generated during the day and store it until
ambient temperature drops.
thermal radiation Electromagnetic radiation emitted by a warm
body — the sun, cousin Frank, the cat, etc.
thermal resistance The ability of a material to impede the flow
of heat. See R-value.
thermosetting baking the organic paint finish on aluminum
to endure a tight bond and long life.
tinted glass Glass other than clear, with a color cast or
tint. Typically tinted glass absorbs and blocks heat, and reduces visible light
transmittance.
tinted glass glass of special formulation to produce
light reducing and/or heat absorbing glass products (bronze, gray or green).
total unit A basis for measurement, evaluation and
performance comparison of different glazing configurations, established by a formula
combining R-values of the frame area, edge of glass area, and center of glass area.
translucent A glazing such as frosted glass, which
transmits electromagnetic radiation (light) but causes scattering so that a clear image
cannot be seen.
transom A window installed above another window or
door.
transom A small window that fits over the top of a
door or window, primarily for additional light and aesthetic value.
transparent Clear glazing which transmits light without
diffusion, and which can be seen through clearly.
tripane An insulating glass unit consisting of three
panes of glass with two internal air spaces.
true divided light A term which refers to windows in which
multiple individual panes of glass or lights are assembled in the sash using muntins. This
traditional method of window construction does not have the strength or durability of the
Integral Light Technology™ used in Pella Architect Series® windows.
U value a measurement of heat transmission. The U
value of a window is measured by the number of BTU’s that will pass through each square
foot of area per degree of temperature difference from one side of the window to the other
(the lower, the better). U value = the number 1 divided by the R value
ultraviolet radiation (uv) Electromagnetic radiation from the sun, with
wavelengths shorter than visible light — UV-caused fading of furnishings, artwork, etc.
after prolonged exposure to direct sunlight can be a problem. Classical measurement of UV
transmittance (300 — 380 nm) is generally used to indicate fading potential and to
compare UV-blocking performance of various glazing types. Krochmann is a damage-weighted
function developed in Europe used by some to compare product performance.
unison lock A casement locking system which secures the
window at two locking points by operation of one handle.
united inches the sum total of one window width and one
window height expressed in inches.
u-value Rate of heat flow-value through the complete
heat barrier, from room air to outside air. The lower the U-value, the better the
insulating value

V-X

 

TERM

MEANING

vent the operating portion of a window that
swings or projects in or out.
vent unit A window or door that opens, to provide
ventilation.
vent unit A window or door unit that opens or
operates.
vinyl A plastic material used by some window for
cladding or entire window units.
visible light transmittance The percentage of visible light (380 to 760
nanometers) that is transmitted through glazing. Visible light transmittance is affected
by special coatings and the number of panes of glass or film in an insulating glass unit.
warm edge spacers Insulating spacers used to seal panes of
glass in the manufacture of insulated glass units — edge conductivity is lessened for
improved window energy performance and reduced condensation problems. Warm edge spacers
include Swiggle Seal® by Tremco Ltd., and HeatSeal* from Southwall
Technologies Inc.
wave length selective “Intelligent” coatings such as Low
E2 and Heat Mirror allow for glazing combinations to permit selective gain or shielding of
the sun’s heat, while letting in visible light.
weather stripping Thin sections of material used to prevent
air leakage around operable windows and doors — usually foam gasketing, metal strips, or
vinyl.
weatherstripping A material or device used to seal the
openings, gaps or cracks of venting window and door units to prevent water and air
infiltration.
wedge glazing a flexible, continuous gasket that ensures a
high compression seal between the glass and glazing bead by applying pressure.
weep slot an opening cut into a window sill and/or
sash rail to allow water to drain to the exterior.
wind load the amount of pressure exerted by the wind
on a window or door generally expressed in pounds per square foot (psf).
windload Force exerted on a surface by moving air.
window size. always expressed as width first, then height
windowpane divider See muntin.  
wire glass 1/4″ clear or obscure glass having a
layer of diamond or square pattern wire mesh embedded in the glass lite.
XUV Fading
Protection
A trademark of Southwall Technologies Inc.
referring to Heat Mirror’s ability to block 99.5% of damaging radiation passing through
residential glazing (a standard dualpane blocks only 42%).
“XO” sliding
window
“O” indicates fixed sash = left
sash slides and right sash is fixed.
“XX” sliding
window
“X” indicates moving sash = both
sash operate.