Home Window Glossary To Help Portland Homeowners

Home WIndow GlossaryYou want to keep your family as comfortable as possible and that starts with your home’s windows.

So, whether you need a window repaired or you’re thinking about replacing windows in your Portland Oregon home, you may need a little help clarifying all the terms related to windows.

This home window glossary explains the parts of a window as well as the types of glazing.

Parts of a window

Jamb-The main vertical parts of the window frame or the molding around a window frame.

Frame-It’s made up of the jamb, head and sill-the entire structure that makes up the opening in which the window sash fits.

Head-Some call this piece the ‘head jamb’ and it’s the main horizontal part that forms the top of the window frame.

Sill-Most people know this one because they hate cleaning it but it’s the main horizontal part that forms the bottom of the window frame (which is why it catches all the dirt).

Apron-Many aren’t familiar with this term-it’s the decorative molding below the window sill.

Sash-It’s the part of the window that holds the glass in place and is made up of stiles and rails within the framework.

Sash lock strike-The lock affixed to the sashes of the double-hung window, it reduces rattling and secures the window when it’s shut.

Balance-Usually a spring-loaded mechanical device used in single and double-paned windows, it counterbalances the weight of the sash when it opens and closes.  The balance spring is the specific part that holds the sash open at any position.Windows Portland

Casing-This refers to all exposed molding or framing around the window (on the interior AND exterior of your house) and it covers the space between the window frame and the wall.

Mullion-A more uncommon term, it’s the vertical strip of wood that sits between 2 or more side-by-side windows.  For example, there would be a mullion separating each pair of windows.

Check rail-In a double-hung window, it refers to the bottom horizontal part of the upper sash and the top horizontal part of the lower sash that meet at the middle of the window.

Weatherstripping-A strip of material (usually insulating foam) that covers the joint between the window sash and frame with the purpose of decreasing air leaks and keep water from seeping into the window.

Gaskets-The rubber strips on window channels to seal it against air and water.

Lock strike-The opening that accepts the bolt of the window (lock).

Terms related to window glass

Glazing-You’ll hear this term a lot though it simply means 1 or more pieces of glass placed in a window sash.

Lite-It describes an individual pane of glass in a window and mostly used when you have a window that’s made up of several smaller panes, as in a 12-lite colonial window.Home WIndow Glossary

Glazing channels-Grooves cut into the sash to hold the glass in place.

Glazing types-This is the treatment and/or layering of the glass.  An example is a low-e coating or double-glazing.

Insulating glass-Any multiple glazed window with a hermetically sealed space (fancy word for air tight) between the pieces of glass, the space usually contains Argon, Krypton or a mixture of the two.

Double-glazing-2 panes of glass with air between them to act as insulation though this can also refer to a single pane window that has a storm window.  As you might have guessed, triple-glazing is 3 panes of glass with air between them (like the window pictured).

Double-paned window-Almost the same as double-glazing but the 2 pieces of glass are inside a single sash.

Gas fills-Krypton and Argon gas is used between panes of glass to increase thermal performance.  Krypton performs better but is more expensive and is best used for smaller spaces-usually ¼ to 3/8 of an inch between glazings.

Less expensive Argon doesn’t perform as well as Krypton and is best used in glazings ½ inch or bigger.  It’s common to find a mixture of the 2 gases used.

Low-emittance coating:  Usually called low-e coating for short, it’s a microscopic metal or metallic oxide that is put onto the glass to decrease thermal radiation and radiant heat transfer.

Low-e glass can be produced with varying amounts to let different levels of heat or ultraviolet light through it.

Tinted glazing-Sometimes called heat-absorbing glass, this is a less expensive method for reducing solar gain.  With this treatment, the glass absorbs the heat whereas glass with the more effective (and costly) low-e coating diverts the heat.  Green, gray and bronze are the most commonly used colors for tinting.

Terms explaining the energy efficiency of windows

Shading coefficient-This measures the amount of radiant heat coming through glass.  It’s a decimal value found when dividing the solar gain of a window into the solar gain of a clear, single-glass window of the same size.  The lower the rating-the better as it means there’s less radiant heat coming through.

Solar heat gain coefficient-Related to shading coefficient, it’s often cited in the performance ratings of window manufacturers, which is why we’re covering it here.  It’s the fraction of radiation coming through the window compared to the amount of radiation hitting the outside of the window.

Spectral selective glazing-This type of glass is fabricated to manage solar heat while still allowing a higher level of visible light to come through.  You may be familiar with the term ’low-emittance glazing’ and this is a type of that.

Ultraviolet transmittance-Percentage of ultraviolet radiation that comes through a window.

U-value-The amount of heat transferred through the window and the lower the U-value, the better the insulation (less heat comes through it).

Visible light transmittance-The percentage of visible light that comes through a window.

Even with this informative home window glossary, you’ll probably have questions so don’t hesitate to contact us here at Sierra Glass.

There’s many options when retrofitting windows (energy efficiency, style, double or triple glazing, etc.) and lots of things for you to consider so our goal is to educate you so you can make a smart decision.


May 3, 2017