Vacuum-Insulated Windows

Many studies show that windows are the biggest energy-losing item in the home. This has been proven by taking infra-red pictures of the home. The bright red squares tell the whole story without wordsa sthis shows where the heat is escaping.

Until about 5 years ago the vast majority of homes were built with double-pane, sealed glass units. Many of the frames were wood and aluminum but vinyl was beginning to make inroads. These windows had an R-value of less than 1.0 – which means that was the resistance to the heat going outside – whereas most walls now are r-19.

Today the standard is triple-pane, low emissivity glass with an argon filling. The argon prevents the convection currents inside the glass, which escalates the heat through the glass in a normal window. The low emissivity coatings (low-e) on the glass reflects the heat back into the home. These still have an r-value of less than R- 5.

U-Value

Rather than deciding the r-value windows are commonly measured in U-value, which is the term used to describe the whole window system’s ability to prevent the loss of heat through the entire window system, the glass, sash and frame. It is usually a small number whereas r-value is a large one and used to describe the individual components like a batt of insulation.

Here is how the system works: A single-pane window glass might as well be an open window as it draws heat to the cold surface and then radiates it outside. As well, a double-pane window has only an R-value of 3 or 4 whereas a typical 2×4 stud wall is 12 to 19.

Vacuum Windows (VIG)

A new system of a vacuum space between the panes is coming to the window industry. Like a thermos the vacuum-insulated glass takes away the convection loss of heat better than a heavy gas which just slows down the process. In this way 2 panes will do a better job than 3 panes of the standard low e and argon window systems. To make up for the lack of pressure between the panes small spacers are added.

Also, by employing VIG with low-e coatings the glass used is thinner. So even adding another pane of thin glass will not make the VIG window that much heavier will make the window’s insulating factor more than double that of the regular triple pane low-e and argon window systems