Insulated Windows

Save Energy and Reduce Costs with Modern Technology

When thinking about insulation, things like glass wool (fiberglass), down jackets and foam often come to mind instead of windows. However, modern fenestration technology can offer tremendous energy savings compared to the past. This reduces monthly heating and cooling bills and your carbon footprint while providing more consistent and comfortable interior temperatures. Imagine pouring hot coffee into a standard glass versus a thermos. The difference between regular and insulated windows is similar.

Construction of Insulated Windows

The design and structure of modern windows is what sets them apart from their outdated single-pane predecessors. First and foremost, they feature a minimum of two panes of glass with three being increasingly common. Each pane is installed individually in the window frame and separated by a 0.4 to 0.8 inch (10 - 120 mm) air cavity. This may be filled with an inert gas like argon or dry air. Along the edges, a spacer bar or warm edge holds each pane in place and separates them. As a whole, they are often referred to as IGUs, or insulating glass units, regardless of whether in doors or windows.

Thus, the major features are:

Multiple glass panes (double or triple glazing)
Gas-filled spaces between panes
Use of a spacer bar between panes
Optional solar control coatings (e.g. low-e)
Low U-values

Replacing old single pane windows with modern insulating glass can significantly cut heat loss and prevent cold air around windows. This leads to more consistent room temperatures and can make heaters and vents near windows and doors unnecessary.

Heat Loss in Windows Explained

Windows lose heat in a number of ways, beginning with the area between the frame and masonry. Professional installation is critical to ensure that the outer area of the frame is installed properly and sealed against air infiltration.

The best window in the world cannot make up for poor installation and gaps with the masonry.

Next, worn seals can allow cold air in and warm air out. Opening mechanisms like hung sash windows constantly rub against the seals every time the window is open and closed leading to their rapid deterioration. Many older windows also feature far fewer seals than those today.

Finally, the frame and glazing itself can lose heat via conduction. With single glazed windows, conduction is a particularly large source of inefficiency. To summarize, heat loss can be attributed to:

Air leakage between the frame and masonry
Air leakage from worn seals
Conduction via the frame
Conduction via glazing.

New windows radically improve insulation in all these areas reducing the overall U_w-value and increasing the R-value.

Argon and Krypton Gas Fillings

While filling a window with a special gas may sound unusual, the reason is simple: they conduct less energy than normal air. Both argon and krypton are clear, non-toxic, odorless and widely used gases in industrial applications. Argon, for example, has approximately 67% of the conductivity of standard air. This means it is more difficult for energy to move through it, thus reducing heat loss. Krypton offers even better performance but is used less frequently due to its higher price.

Warm Edge Spacers or Swiss Spacers

While double glazing and triple glazing create a series of insulating layers and gas fillings reduce the transfer of energy, the panes must still be all firmly held in place and their airtight seal maintained. Warm edge spacer bars are the solution. In the past, they were frequently made of aluminum for its stability and strength. However, aluminum is an excellent conductor of heat and created a thermal bridge between the inside and outside. This leads to both energy loss and condensation between panes.

Warm edge spacers are typically made of stainless steel, which has a much lower conductivity than aluminum, or of a plastic composite. Not only do they help improve the overall U-value, but they keep the panes stable. They often feature desiccants to eliminate moisture and create an airtight seal to both prevent moisture vapor getting in and gas from leaking out. Without this, the gas will eventually leak completely and condensation can build up potentially leading to mold.

Extruder-manufactured sealing for excellent weather protection

Unplasticized PVC profiles usually consist of a multi-chamber system featuring five or even six different chambers. Insulated windows for passive houses typically feature six chambers. Many standard models have additional steel reinforcements in the profile while those with higher energy efficiency use carbon fiber in its place and even go so far as to fill the chambers with a special foam.

The entire profile is filled with a special insulating foam, improving thermal insulation and even its strength and security. Furthermore, passive house windows feature special vinyl reinforcements fixed to the window's edges. This technology helps to ensure a stability that even steel-reinforced windows cannot reach, as those do not take the corners into account.

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