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Windows 101

When you are familiar with window terminology, it will be easy for you to identify and to buy the right type of window for your home. Windows last basically 20-25 years; as a result purchasing new windows is not a frequent priority for home owners. Over the last 20 years, there have been many changes in technology and performance standards in the industry of developing windows. Terminologies that are frequently used in the window industry have been listed in the fact sheet.

Components of a window

Windows have the following components:


  • Mullion
  • Head
  • Nailing flange
  • Sill


  • Hardware
  • Rail
  • Stile



This refers to the vertical and horizontal parts that usually surround the sash. The sash is hung on this part too. Frames are made of the same material that makes sash. The manufacturing of windows frames can be done with or without flanges. Sash and frame designs are very important since they enhance both appearance and energy efficiency. A number of materials are used during manufacturing:

Wood frames can be painted using any color according to the customer’s choice, and they are characterized by high insulation properties. In order to prevent damage by moisture, they require recurrent maintenance. These frames are also cheaper compared to frames made of other material. There are also other wood frames know as clad wood frames. These frames are mainly characterized by the insulating quality that comes naturally. They also require less maintenance. Cladding is made of vinyl or aluminum, and is available in a number of colours. When the cladding is properly applied on the wood, moisture problems are reduced. Damage and lot occurs unseen in case moisture gets trapped in the area that is between the cladding and the wood.

Aluminum frames are durable and strong although they easily conduct heat. In order to avoid condensation and heat loss, the national Building code of Canada requires the frames to have a heat barrier inside that has been made from wood, rigid foam or polyurethane in order to reduce heat transfer. Aluminum frames have very poor insulating properties. However, these frames require little maintenance, and are very durable. Aluminum frames are also characterized by mitred joints in corners, and this is an allowance for water to leak into the walls in cases that the water is not well sealed or when the seal fails incase.

There are two available types of vinyl frames

  1. Extruded vinyl frames that incorporate internal air cavities.
  2. A reinforcement inner structure made of wood or metal material. Since wood has better insulating qualities than metal, this makes it preferable.

Vinyl frames require little efforts to maintain, and are very durable. They also have the ability to resist color fading, termites, moisture, corrosion as well as air pollutants. It is also easy to shape the material to the required dimensions.  Windows made of vinyl have the ability to provide good insulating properties at home. The effect is even excellent in cases where the sash and the frames are well insulated.

There are also other relatively new frames known as fiberglass frames. These frames are strong, durable and light. Even the narrow sizes of fiberglass have very good insulating abilities. These frames neither expand nor contract with heat or cold when they are compared with other frames. Fiberglass frames are more expensive when compared with other window types.


The glass can either be a number of panes that have been divided by a mullion or just a solid glass sheet. A mullion is a frame that is used to hold the window panes in the sash. In order to prevent breakage, some glazings are made up of tempered glass or laminated glass. The use of laminated glass ensures that in case of a window accident, that glass shards are too small to even cause injury.

Double gazed windows are made of two layers. These two layers of glass have been separated with a spacer. This is the minimum standard that the national Building code of Canada has allowed. The air that is trapped between the two glass layers is a provision for some insulating value.

Triple glazed windows are characterized by the usage of three glass layers. It can also be composed of two layers that have a low emissivity (Low-E) film that has been suspended between them. The additional layer. The air space, and the additional layer is the reason that triple glazing has a better insulation value compared to double gazing. In areas that mainly have weather and temperature extremes, it is a good choice. In cases where noise from the outside is a problem, triple gazed windows are the best. This is because they help to reduce sound transmission. The sash is heavier, and this makes it more difficult to operate the window than the double gazed sash.

Glazing Technology

Low emissivity is made up of a layer of metal oxide that is applied in the outer face of the inner gazing found in a double glazed window. The coating freely allows sunlight to pass, and blocks heat from escaping at the same time. Double glazed low-E is a provision for a similar insulation. However it costs less and weighs less. Low-E has the ability to filter out the ultraviolet rays of the sun which are potentially harmful by fading furnishings, and have the ability to reduce condensation of the window by keeping the frame warmer.

The window technology has also come up with inert gas fill, The unit between window panes and gas is filled with krypton or argon gas. Inert gases usually have a higher insulation value compared to air since they are usually denser and have a lower thermal conductivity when compared with air. This results to power heat transmission between glass panes. Due to its low cost and availability of argon, it is the most commonly used gas. Filling gas in window panes is a cost effective way of upgrading your window glazing.

One can get glazing of different colors in order to cause a reduction in solar heating as well as glare control. The technique is commonly used in multi residential or commercial high-rise buildings. Purchasing films in order to use them to reduce the sun’s glare is an option that is commonly used. Another way of reducing glare is through using outdoors, shutters or window awnings. The application of tinted films should only be done by qualified contractors since the process requires special tools and skills.


Windows are either operable or fixed. Windows that are fixed cannot open. Operable windows have a unit of rails and stiles which hold the glass that has the ability to move when the window opens, which is sash. These sashes are found in a number of hinged or sliding models. The sash is made of fiberglass, wood, vinyl or metal and it is supposed to make a tight seal with the frame at the time the window is closed.In cases when the seal is too tight, the window’s operable motion becomes hard to operate.

Spacer Bars

Spacer bars are found at the perimeter of the glazing unit that has been sealed in order to provide equal separation in the spaces in between the spaces of glass in multiplied paned windows. Spacer bars are mainly made of aluminum but it is possible to find spacers that are made up of less conductive materials. When a window has a high performance space, it increases its performance as well as energy efficiency. However, the frame should always be made of insulating materials.

Spacers have the ability to incorporate desiccant which absorbs moisture from air that is trapped in the space between glass. The moisture trapped prevents fogging and condensation. In case you window fogs, this is s assign that your seal is broken.


This is a term used to describe the mouldings that are found surrounding the cover frame and the window.


The hardware that may be found in a working window may include latches, hinges, cranks and levers. Some windows also have locks for security purpose. Crescent shaped locks are the standard locks that are supposed to be used on double hung and single hung windows.

Weather stripping

This is a component that is found in operable windows. It provides a seal between operable sash and the window frame. It is used as a way of avoiding air leakage. Good weather stripping is a sure way that the performance of the window is also good. There are two main categories of weather-stripping.

Brush type seals or wiper, also known as mohair are very common among sliding windows, and usually wear out more quickly as a result of the type of window operation. Brush type seals are also very likely to be used as exterior weather seals. They can also tear easily incase the window is opened when seals are embedded on frost or ice.

Compression seals which are sometimes called bulb are more likely to be fragile during the times of cold weather. These seals may also crack in case the seal walls are too thin or the window is operational during cold weather.

The most vulnerable component of an operable window is weather stripping. This is because it receives the most wear and tear. It is advisable to check the seals on yearly basis to check for any signs of damage or wear, and replace if it is necessary.

*The source of information is: CMCH Web site

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