Foam Filled Window Frames
|Foam Filled Replacement Windows|
|Foam Filled Replacement Window Frames|
|A new type of replacement window frame, foam filled replacement windows, offer homeowners a new enhanced replacement window choice.|
Foam filled replacement window frames are an optional choice for aluminum, vinyl or fiberglass windows.
 Foam Filled Window Frames
Foam-filled replacement windows are marketed as sturdy replacement window frames that provide a more energy-efficient frame than a non-foam filled frame. Since a frame’s durability and thermal performance is determined by additional elements of a window’s construction, customers should review the total performance of any type of window frame, including the materials that cover a frame, glazing and weatherstripping. Foam filled window frames are filled with a urethane foam filling.
 Framing Materials
Vinyl, aluminum and fiberglass frames can be filled with foam. These materials are, according to the U.S. Department of Energy (DOE), good framing insulators. Standard aluminum, fiberglass and vinyl window frames have hollow channels inside them which offer higher insulating capabilities when they are filled with foam.
 Fiberglass Frames
Fiberglass consists of stands of fiber which are mixed with glass or silica, making it the best insulator since the fiber content in the fiberglass increases its ability to control heat conduction.
 Vinyl Frames
Vinyl provides more thermal resistance than metal because it conducts less heat. This ensures that the vinyl window frame remains cooler than metal frames in hot weather and warmer than the metal frames in cold weather.
The hollow channels that exist within aluminum, vinyl or fiberglass window frames can be filled with foam to create an insulated foam-filled window frame. According to the DOE the foam improves the insulating performance of both vinyl and fiberglass frames, though the extent of the added insulating is debatable. The insulating foam also may improve a frame's structural strength by keeping the window from bending out of shape due to small shifts in a home's foundation.
 Window Construction
Each section of a placement window contributes to the window's overall energy efficiency in a different way. If other parts of a window are air-tight and well insulated, the foam-filled fiberglass or vinyl window frame will also add to its overall thermal performance. If, for instance, the area between the windowpane and the frame is not airtight, cold or hot air will leak through the frame in both the summer and the winter, reducing the window's thermal performance, whether or not the frames are foam filled. The performance of foam-filled replacement window frames is only as good as the construction quality of the entire window. Efficiency Rating According to the National Academy of Engineering foam-filled window frames with airtight window panes and other thermal insulating design elements can produce windows with "R" values as high as 7. (While the U-factor is used to express the insulation value of windows, R-value is used for insulation in other areas of the home (walls, floors, roofs, etc). To compare the R-value and U-factor it is necessary to divide the U-factor number by 1 -- a 0.25 U-factor equals 1/0.25 = 4 R-value). The NAE estimates that energy lost through poorly insulated windows accounts for about 30 percent of the energy used to heat and cool a home.
 Considerations of Foam-Filled Window Frames
There are different considerations for buying windows in which the frames include foam fillings. Buying windows with frames that have foam fillings may appear to be an efficient way to get better thermal performance from windows. Foam has been especially successful in the vinyl, aluminum and fiberglass window industries because those frames include either one or two chambers, enabling, proponants claim, the foam filling to increase their insulating capabilities. In addition, aluminum and fiberglass windows are manufactured with mechanically joined corners that ensure that the foam does not interfere with the strength of the joint.
Some window manufacturers believe that if a window is well designed the foam insulating will not provide any increase in the windows' insulating value and can possibly cause problems that actually deter from the windows' insulating capabilities. Reducing the air pockets in a window frame reduces the hollow chambers, resulting in a weaker window and lowering the insulating performance. Hollow window frames enable air to circulate within the frame which adds to the insulating value of the window.
Foam cannot go completely into the corners of a window or it will contaminate and weaken the welds.
Independent laboratory tests indicate that the interior surface of a foam filled vinyl frame is approximately 3°F warmer than that of an uninsulated frame in sub-zero temperatures.
 Sound Insulation
Foam filling is touted as providing enhanced sound insulation. Not all industry observers agree, noting that hollow chambers in a window's frame also insulates against sound.
The main value of a foam-filled window involves stiffening the window frame to make it more rigid and sturdy. A frame makes up approximately 1/10th of the total window area and accounts for 2% - 3% of total heat loss. This provides only minimal thermal insulating value but maximizes the opportunity to strengthen a window's flexible hollow frame.