What are Double Pane Windows?  

Are you looking for ways to lower energy consumption in your office or home? The Double Pane replacement windows are ideal for lowering costs and being more environmentally friendly than single pane windows.

These types of glasses go by various names in the literature. They have been called insulated glass units, doubled glazed units, or sealed glass units. The types of glasses are often used these days in the residential and commercial sectors as they provide much better insulation than their single pane counterparts.


“Double pane window” consists of a singular sealed unit of two panes or triple panes of tempered or laminated glass (sometimes referred to as lites), which are separated by a spacer. The space between the two panes is either filled with air or an inert gas. If these units are to be replaced, they will have to be done as a unit too. The insulating layer created by the gas between the glass plates dissipates the heat transfer.

double pane windows replacement

The components of a double pane windows as discussed above are a) Glass pane, b) Spacer, c) Gas Type and d) Window Frame. The best choice of what specification of the window is best suited for a project depends how the unit will be used, benefits they provide and what you want to achieve. Lets see how each element can be customized.


The glass panes of a double pane windows unit can be laminated or tempered to meet safety standards and meet building requirements. Both are strong, durable, and shatter-resistant and vary in their fabrication methods. The exterior or outside facing of double pane windows can be a solar control glass and the inner pane can be ordinary or thermal insulating glass.

Multiple combinations can be designed according to the requirements of each building. The glass pane can come in a range of thicknesses. Usually, since these are sold as a single unit, the dual pane’s total thickness rounded to the nearest 1/16 of an inch is what is specified. You can buy them in thicknesses of 1/2″, 5/8″, 3/4″, 7/8″ or 1″.

In addition the glass panes can be coated with Low-E(low emissivity) coatings, can come with standard and high-performance tinted glass, can have reflective coatings, or can have silkscreen glazing to meet various aesthetic and thermal performance requirements. It can be designed to meet state energy and safety regulations, can be designed for light, solar and sound control, shock, hurricane and earthquake resistant.


The insulated glass unit has a spacer layer(also known as a dessicant layer) that separates the two glass panes. The two panels meet at the edges of the window frame and are sealed together by an a primary sealant made of polyisobutylene.

A secondary sealant made of silicone is also sometimes used depending on the application. The spacer gap can come in a variety of thicknesses ranging from 3/16″ to 1″. For example, a standard 1″ thick double pane windows unit might consist of two panes of 1/4″ glass and a nominal 1/2″ air space. 

The reason the spacer is referred to as a desiccant layer is because it contains a desiccant material(such as silica or zeolite) which serves as a drying agent and performs the role of absorbing the humidity inside the IGU and seals the moisture.


The space between the two panes can be filled with air or other gases. Typically air-filled units may have a longer life because the sealants are long-lasting. The spacer layer can also be filled with inert gases, such as argon or krypton, to improve the insulation performance of the unit.

But they do come at an increased price and could result in reduced life of the unit due to gasket failure. And in cases of failure, the entire window unit has to be replaced. Which is why finding a good professional that performs window replacement is a must.


This is not really a part of the double pane windows but needs to be mentioned if you are replacing your windows and frames completely. The panels are fixed in a frame which comes in a variety of materials such as vinyl, wood, aluminum, and fiberglass. For homes, vinyl is a popular material that is made from rigid polyvinyl chloride. Vinyl windows are long-lasting and do not rot easily.  

The double pane windows units can be further customized based on dimensions required for the project, spacer bar colors, glass shapes, and grid colors. The spacer thickness, panel thickness, and a variety of glass types can be chosen. For example, if you want to use glazed glass windows it will make its insulation more effective. The other types of glasses used are ceramic, annealed, tempered, or laminated.


The thermal performance of insulated glass is determined by the thickness of the glass and the insulating space between each pane. The glass unit can be designed to increase solar radiation that passes through the window’s glazing. Simply put the amount of sun’s heat that enters the building. The short wave infrared energy from the sun is converted into heat when it strikes the window panel.

The heat energy is re-radiated from the panel towards the interior of the house and is referred to as long wave infrared radiation. This heat is then stored as solar mass within the building if the windows are tailored to prevent the heat escape. So houses in the mid-Atlantic and northeast which end up with greater heating demands can rely on this passive solar heating technique to reduce their energy cost by heating up the interior space.

Also using Low-E Coatings one can reflect the heat back into the room. In summer months, the Low E coating could assist in rejecting the sun’s UV and infrared light that passes through the window.

In summer months, these windows allow more heat to enter the building causing overheating and can increase cooling costs. The key to choosing the right window relies on a parameter known as Solar Heat Gain Coefficient which varies between 0 and 1. Too high and you risk warming the house during the cooler months and rake up cooling costs and too low and you lose out in the winter months. Choosing the right balance is key.

Additional window coatings can be combined with double pane windows to create an efficient window that also reflects sunlight in warm climates or even absorbs and contains sunlight in colder climates. Coatings are applied on the interior of IGUs to reflect UV light back into homes to retain warmth, or on the outside to keep sunlight from heating up a home. For maximum performance, multiple surfaces of the IGU can be coated, though this comes at a higher cost. In double-pane windows there are four surfaces that can be coated.

Our technical staff are trained to assist potential buyers on the right choice of double pane windows or insulated glass units for their home or office.


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