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Glossary of Window Terms

Air Infiltration

Air that leaks in and out of a home or building through cracks in walls, windows and doors is considered “infiltration”. The lower a window’s air infiltration rating, the more airtight it is.

Argon and Krypton

Argon and krypton are odorless, colourless, non-toxic inert gases that can be used instead of air between panes of glass to increase insulation and energy efficiency. Argon is the cheaper, more readily available gas, but krypton is a better insulator. Often, manufacturers will use a blend of air, argon, and/or krypton to balance cost and performance.

Cam Lock

Cam locks are thumb-turn locks that are traditionally used on vertical and horizontal sliders. They reduce drafts by tightening the sashes together and provide superior security.



Condensation on windows occurs when the surface temperature of the glass (glazing), sash or frame is lower than that of the humid air around it. The moisture vapour in the air changes into liquid water on contact with these cold surfaces.

  • Exterior CondensationEnergy-efficient windows will occasionally have condensation on the exterior glass surface. This usually happens during periods of warm weather and high humidity near the time of sunrise. Because energy-efficient windows greatly reduce the amount of heat escaping to the outside (which is good during the long periods of cold weather), the exterior glass surface is cool enough to allow condensation to form for a short period of time.

Condensation Resistance (CR)

CR measures how well a product resists the formation of condensation. CR is reported on a scale of 1 to 100. The higher the number, the better a product is at resisting condensation.

Energy Rating System (ER)

A window’s ER rating is a measure of its overall performance, based on three factors: 1) solar heat gains; 2) heat loss through frames, spacer and glass; and 3) air leakage heat loss. All window Energy Ratings (ER) are evaluated in the same way.

Energy Star® Symbol

The international Energy Star® symbol is a simple way for consumers to identify products that are among the most energy-efficient on the market. Only manufacturers and retailers whose products meet the Energy Star® criteria can label their products with this symbol. Choosing an Energy Star® labeled product over a conventional model could save you hundreds of dollars in energy costs.

Canada and the United States have long been involved in the Energy Star® program and utilize a zone default qualification schedule. Qualifications are based on “U-Factors” and “SHGC” (solar heat gain coefficient), or “ER Ratings” in Canada.


Extrusions are made through a manufacturing process in which PVC (polyvinyl chloride) is melted, shaped into a continuous profile, and cut to length. North Star’s AAMA-certified multi-chambered vinyl extrusions are made in our own quality controlled state-of-the-art manufacturing plant.

Fold-Down Handle

Fold Down Handle

Optional fold-down handles offer a sleeker profile, are less obtrusive to your opening and allow window treatments to close better.


Contour and Flat grilles add a decorative element to windows and are available in many styles. Choose a standard size or customize to the dramatic shapes of our architectural windows. Available in white, ivory, hickory, chestnut brown, cocoa, sable, sandalwood, brass and pewter. These grilles offer a perfect accent to any window.

Insulated Glass

super spacer

Any window that features at least two or more panes of glass spaced apart to form a sealed glazed unit. The space between panes provides added insulation.

Low-E Glass

Low-E stands for low-emissivity. Emissivity is a measure of how much a glass surface transfers radiant heat.

LoE 366 (Cardinal) 

LoE 366 – Is recommended when cooling costs outweigh heating costs in your energy usage, or where summer discomfort from heat build-up should be an important concern. This is the best glass for most applications in a southern climate. It has a very high reflection rate of the radiant outside heat to prevent heat gain in summer and in winter it still retains radiant once you turn on your furnace! LoE 366 has a lower Solar Heat Gain Coefficient (SHGC) in order to minimize Solar Heat Gain that results in extra work for your air conditioning unit.

LOF (Libby Owens Ford) / Pilkington Energy Advantage

LOF – Pilkington Energy Advantage Low-E is the best glass for most applications in a northern climate. It has a very high retention rate of the heat in your home in winter and prevents heat gain in summer. Energy Advantage Glass has a higher Solar Heat Gain Coefficient (SHGC) than Low-E glass designed for southern climates. It provides free winter heat for your home. Since as much as 95% of your energy expense for heating and cooling combined is for heating, this glass is more cost effective than other glass without a high SHGC.


The R-value represents the resistance a material has to heat flow. It measures the effectiveness of insulation in stopping heat flow. The higher the R-value, the greater the heat resistance.

Screen Pull Tabs

Screen pull tabs are constructed from a durable nylon material and are installed as an integral part of the screen itself, for ease of removal.

Solar Heat Gain Coefficient (SHGC)

When cooling is needed, the key rating parameter is the SHGC. SHGC measures how well a product blocks heat from the sun. SHGC is expressed as a number between 0 and 1. The lower the SGHC, the better a product is at blocking unwanted heat gain. Blocking solar heat gain is particularly important during the summer.

Super Spacer

super spacer

A highly UV-resistant and, flexible silicone foam designed as the spacer between glass panes in sealed unit production. Units constructed of super spacer satisfy the toughest warm edge demands by:

  • resisting condensation
  • reducing energy costs
  • providing long-life durability
  • reducing outside noise distractions


When heating is needed, the key rating parameter is the U-value. The U-value describes how well a product prevents heat from escaping a home or building. U-value ratings generally fall between 0.2 and 1.2. The lower the U-value, the better a product is at keeping heat in. U-factor is particularly important during the winter heating season.

When purchasing energy efficient windows, doors, and skylights, it is more important to consider whole-unit U-factor (a measure of insulation) and Solar Heat Gain Coefficients (SHGCs) (a measure of how well the product blocks heat caused by the sun) rather than the specific materials or technologies used. The ideal U-factor and SHGC vary depending on the product and/or your climate zone.

Visible Transmittance (VT)

The VT is the relative amount of visible light transmitted through a pane of glass. The VT ranges from 0 to 1. The smaller the VT, the less visible light is transmitted through the product. The higher the VT, the greater the potential for day lighting to offset the need for electric lighting.

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