Houston Window Glossary
Windows can be one of the most confusing things to purchase. U-Value, R-Value, Low-E…it’s like learning a new language! And what do they have to do with the new window you are purchasing?
We’ve put together a Houston window glossary you’ll commonly run into during the purchasing process. Knowing them will help you better communicate with your window contractor about your needs. And of course, if you ever have any questions about Houston windows, give the team at Best Investments a call at 281-852-1866.
U-Factor: The rate of heat loss in a window. The lower the U-Factor, the greater its resistance to heat flow, and the harder it is for heat to escape your home during winter.
SHGC: Shows the fraction of solar radiation let through a window. The lower the SHGC, the less heat that gets into your home (VERY important for those Houston summers!). The SHGC rating will always be between 0 and 1.
UV: Measures the amount of damaging ultraviolet light that is blocked from being transmitted through the glass.
Visible Transmittance: The percentage of visible light (390 to 770 nanometers) within the solar spectrum that is transmitted through glass..
Condensation Resistance: Condensation Resistance (CR) measures how well a product resists the formation of condensation. CR is expressed as a number between 1 and 100. The higher the number, the better a product is able to resist condensation.
Fading Transmission: The portion of energy transmitted in a spectral region from 300 to 600 nanometers. This region includes all of the ultraviolet energy and part of the visible spectrum, and will give the best representation of relative fading rates. The lower the number, the better the glass is for reducing fading potential of carpets and interior furnishings.
Air Infiltration: The amount of air that passes between a window sash and frame. In windows it is measured in terms of cubic feet or air per minute, per square foot of area. The lower the number, the less air the window lets pass through.
Low-E Glass: Glass with a transparent metallic oxide coating applied onto or into a glass surface. The coating allows short-wave energy to pass through but reflects long-wave infrared energy which improves the U-value.
ENERGY STAR, everywhere.
The goal of the ENERGY STAR Windows program is to be better than code. LoĒ³-366 is the one low-E product that can qualify in all 4 climate zones: superior insulating value in the north, and clear solar control for everywhere else in the country.
Double-Hung: A window that has two operable sash which slide vertically.
Single-Hung: A window that has an operable sash on the bottom and a fixed sash on the top.
Casement: A window with a side-hinged sash that opens outward for ventilation.
Picture: A window that has no moveable sash
Slider: A window in which the sash move horizontally.
Awning: A top-hinged window that swings outward for ventilation.
Bay: An angled combination of three windows that project out from the wall of the home. The windows are commonly joined at 30- or 45-degree angles.
Air Chambers – Small honeycomb spaces within the sash and frame, which help to insulate and strengthen the window.
Air Infiltration – The amount of air that passes between a window sash and frame. In windows it is measured in terms of cubic feet or air per minute, per square foot of area. The lower the number, the less air the window lets pass through.
Argon Gas – An odorless, colorless, tasteless, non-toxic gas, which is six times more dense than air. It is used to replace air between the glass panes to reduce temperature transfer.
Awning – A top-hinged window that swings outward for ventilation.
Bay Window – An angled combination of three windows that project out from the wall of the home. The windows are commonly joined at 30- or 45-degree angles.
Beveled Exterior – An angled extension from the frame that adds an aesthetically-pleasing dimension to the exterior of the window.
Bow Window – An angled combination of windows in 3-, 4- or 5-lite configurations. The windows are attached at 10-degree angles to project a more circular, arced appearance.
Cam Lock and Keeper – The mechanisms which pull the sash together when placed in the locked position.
Casement – A window with a side-hinged sash that opens outward for ventilation.
Condensation Resistance Factor – A measure of the effectiveness of a window or glazing system to reduce the potential for condensation. The higher the condensation resistance factor, the more efficient the window and glazing system.
Constant Coil Spring Balance System – Device for holding vertically sliding sash in any desired position through the use of a spring or weight to counterbalance the weight of the sash.
Dead-air Space – The space between the panes of glass of an I.G. unit.
Double Hung – A window that has two operable sash which slide vertically.
Double-strength Glass – Glass with a thickness of approximately 1/8″.
Egress Code – The code that requires a minimum opening of a window for persons to exit or firefighters to enter a building.
Extruded Screen Frame – Different from a Rollformed frame, this frame is pressed through a form or die.
Fusion-welded – The process of joining materials by melting them together with extreme heat (over 500�F), resulting in the materials uniting into a one-piece unit.
Geometric – Specially designed windows classified as either Straight line Geometrics such as rectangles, triangles, trapezoid, octagons, pentagons, etc., or Radius Geometrics which include Half-rounds, Quarter-rounds, Circles, Ellipses, Eyebrows, etc.
Glass – An inorganic transparent material composed of sand (silica), soda (sodium bicarbonate), and lime (calcium carbonate) with small quantities of alumina, boric or magnesia oxides. Available Styles: clear, bronze tinted and grey tinted.
Glazing – The process of sealing the glass to the sash.
Grids – Decorative horizontal or vertical bars installed between the glass panes to create the appearance of the sash being dividing into smaller lites of glass.
Head – The horizontal top portion of the main frame.
Hopper – A window with a bottom-hinged sash that opens inward for ventilation.
I.G. Unit (Insulating Glass Unit) – Two or more lites of glass separated by a spacer and hermetically sealed at the glass edges.
Intercept Spacer System – Spacer system using a U-channel design to reduce the number of conduction paths.
J-channel – Integral extension on the outside of a new construction window that eases installation on siding applications.
Jamb – Vertical sections of the main frame.
Krypton Gas – An inert, odorless, colorless, tasteless, non-toxic gas which is about 12 times denser than air. It is used to replace air between the glass panes to reduce temperature transfer and deter convection.
Laminated Glass – Specially designed glass where two panes of glass are bonded to a durable interlayer, providing increased safety, UV protection and noise reduction. If the window or door gets broken the glass will adhere to the to the plastic interlayer-preventing glass fallout in the home.
Lift Handle – A handhold for raising and lowering the sash. Handle implies that the handhold is not continuous across the sash.
Lift Rail – A handhold for raising and lowering the sash. Rail implies that the handhold is continuous across the sash.
Lite – A unit of glass in a window.
Lock Rail – The horizontal section of the sash where the cam lock is attached.
Lock Stile – The vertical section of the sash where the cam lock is attached.
Low E (Emissivity) Glass – Glass with a transparent metallic oxide coating applied onto or into a glass surface. The coating allows short-wave energy to pass through but reflects long-wave infrared energy which improves the U-value.
Main Frame – The head, sill and jambs sections of a window.
Meeting Rail – The horizontal sections of a pair of sash that meet when the sash are closed.
Meeting Stile – The vertical section of a pair of sash that meet when the sash are closed.
Mesh – Fabric made of either fiberglass or aluminum, used in the making of screens.
Mullion – A vertical or horizontal connecting unit between two or more windows.
Nailing Fin – An extrusion attached to the main frame of a window used to secure the unit to the rough opening.
Obscure Glass – Glass that has been made translucent instead of transparent.
Oriel – A window with the meeting rail located off center of the frame. Most oriels have a 60/40 configuration.
Overlapping and Interlocking Meeting Rail – A meeting rail which overlaps and interlocks both sash.
Patio Door – A glass door that slides open and close on adjustable tandem rollers. Available in 2- or 3-lite configurations with the operable panel available in any position.
Roll-formed Screen Frame – A method of fabrication in which a flat (usually metal) material is placed on a machine where the material is formed into shape using differently shaped rollers and pressure.
Sash – The part of the window which contains the glass.
Shading Coefficient – The ratio of solar heat that is transferred through a glazing material relative to the solar heat transferred through 1/8″ clear glass. The lower the number the more efficient the window is at reducing solar heat gain.
Sill – The horizontal, bottom section of the main frame.
Single-strength Glass – Glass with a thickness of approximately 3/32″.
Sloped sill – The sill of the window that has a downward slope to the outside. This sill has sufficient degree of slope to aid in water runoff.
Spacer – Material placed between two or more pieces of glass in order to maintain a uniform width between the glass, and prevent sealant distortion.
Tempered Glass – Glass with a surface compression of not less than 10,000 psi, or an edge compression of not less than 9,700 psi. When broken, the glass breaks into pebbles instead of shards.
Tilt Latch – Mechanism that unlocks the sash and allows it to tilt in from the main frame.
Tilt-in/lift-out Sash – A sash that can be tilted to the interior and removed for cleaning and is manufactured by welding.
Weep Slots – Slots or holes in the sill (bottom) member of the sash frame that allows water to escape. Weep flaps add a vinyl flap to keep insects out.
Best Investments – Houston Windows since 1977
If you still have questions after looking at our Houston window glossary, or are looking for a quote, contact Best Investments Siding and Windows. We’ll schedule a free and fair at-home replacement window estimate. During this time, we’ll inspect your current windows, discuss your needs and budget, and recommend a window package at a price that will work for you.