Frequently Asked Questions About Windows

Frequently Asked Window Questions

How often should residential windows be replaced?

Homeowners with windows over 25 years old should consider replacing them, both to gain the best energy efficiencies and to protect the “envelope” of the house. A home is an ideal candidate for a window replacement if its windows are sealed or painted shut, experiences ice buildup or a frosty glaze during the winter, gets fogged with condensation or has drafts that come through the windows.

Do replacement windows really pay for themselves or is that just a sales line?

It’s true, if you select high-quality, energy-efficient windows. Savings will vary, but expertly engineered and well-built windows lower home energy consumption. With vinyl-framed windows, maintenance is also virtually eliminated. No need to scrape and paint windows.
These energy and maintenance savings will allow you to recoup your window investment over time.

Will new windows eliminate condensation?

Actually, no. Condensation is moisture vapor suspended in the air, and that’s something no one can guarantee to eliminate. However, high-quality vinyl windows incorporating warm-edge technology glazing systems will help to reduce condensation because they’re much less thermally conductive than other window types. They can help keep the temperature of the window warmer—minimizing the hot and cold differences that turn moisture into condensation.

What makes a window or door energy efficient?

Numerous factors, including how the frame and sashes are engineered and built, the type of glass used (single-, double- or triple-pane), the weather-stripping, the type of low-emissivity coating on the glass and the presence of argon or krypton gas.

What is ENERGY STAR®—and what does it have to do with windows and doors?

ENERGY STAR is a U.S. government program—administered by the Department of Energy and the Environmental Protection Agency with the cooperation of manufacturers—that’s designed to reduce the consumption of fossil fuels through the education of consumers. The program covers many different types of products. Windows and doors can only carry the ENERGY STAR label if they are tested by an independent laboratory through the NFRC program and meet specific, predetermined U-value ratings. By selecting ENERGY STAR products, you will reduce your energy costs and help make the environment cleaner.

What is the NFRC and what should I know about it?

NFRC stands for the National Fenestration Rating Council. It’s a program established by the U.S. Department of Energy to help consumers compare window products and options. Window manufacturers participating in the program are required to label every window to its specific thermal performance level. Customers are then ensured that the products they select meet the requirements for their application. Participation in the NFRC program is voluntary. Not all manufacturers participate because it requires outside third party inspection and extensive product testing.

What does Low E stand for?

Low E is a non-visible, microscopic layer of silver coating added to glass for greater energy efficiency and increased comfort. Low E stands for “low emissivity”, which is the action of reflecting light passing through glass. By reflecting part of the light spectrum (the part that transmits heat), we reduce a window’s U-Value and increase its R-Value.

What do U-values and R-values really mean?

U-Values represent the amount of heat that escapes through a wall, window, roof or other surface. The lower the U-Value, the more energy efficient a material is. R-Values are the direct opposite. These measure an object’s resistance to heat flow. The higher a material’s R-Value, the lower its U-Value, and the less energy it will lose. An R-Value depends on the number of layers of glass in a window, what type of gas is between those layers, and whether one or more of those layers of glazing have been treated with a Low E coating.

Can windows keep out UV radiation that fades carpeting, furniture, draperies and upholstery?

Using a low-emissivity glass in your new windows or doors will filter more than 50 percent of the damaging UV light. The absolute most effective glass for this purpose, however, is laminated insulating glass. It features a polyvinyl butyral inner layer and a low-emissivity coating that filters more than 99 percent of UV radiation that fades interior furnishings.

Can windows and doors reduce outside noise?

All windows and doors reduce noise to some degree. The best solution, however, is to use a laminated, insulating glass system in windows and doors. It provides as much as a 100 percent improvement in sound deadening over other glass types.

What are some common styles of windows on the market today?

Depending on region and personal style, single-hung, double hung, casement, awning, slide-by, bay and bow windows are the most frequently used. A number of other style windows are frequently employed as accent windows.

What is an awning window?

An awning window is hinged at the top and swings out at the bottom to open, operated by a cranking mechanism.

What is a bay window?

A bay window is a series of usually three windows assembled in a polygon shape that projects outward from the side of a house.

How does this differ from a bow window?

Bow windows are very similar to bays, in that they also project from the side of a house. However, they are usually
composed of a series of five window units assembled in an arc, rather than a polygon.

What is a casement window?

A casement window is a window unit hinged at the side that swings outward, operated by a cranking mechanism.

What is a gas-filled window?

Modern window technology permits an inert gas, usually argon, to be sealed between the panes of glass in a window instead of air. The gas is a far better insulator that just air, thus further increasing the thermal value of a window.

What is insulated glass?

Technically, there are two or more panes of glass separated by insulation at the edges and air in the center to provide greater thermal efficiency to a window.

How do I know what type of glazing is right for a window?

Different climates and styles of homes require different glazing options to maximize their energy efficiency. Some glazing options can also help reduce outdoor traffic noise from entering the home. Options range from single glazed glass, as in historic homes (minimal insulating value), up to R10, which features dual-sealed, triple-insulated glass with two Low E surfaces and two krypton/argon gas-filled insulated airspaces for maxi¬mum efficiency.

How do I decide between single-, double-, or triple-glazed windows?

Single-glazing is a single pane of glass and is best used in garages and tool sheds—buildings that don’t need to be extremely energy efficient. Double-glazed windows have two panes of glass with either air or a safe, colorless and odorless gas tightly sealed between the panes. When its glass is treated with Low E coating, the window can achieve a value of R5 at the center point of the glass. The most energy efficient window is a triple-glazed window. Gases are sealed between three panes of glass and Low E coatings are applied on two of the panes. This can bring the energy efficiency up to a value of R10 at the center point of the glass.

Does argon or krypton gas between glass panes really make a difference in energy efficiency?

For air to insulate well, it needs to be as still as possible because moving air carries energy. Both argon and krypton are heavier than air—so they’re less prone to convection or thermal movement. The bottom line is that heavier-than-air gases offer a higher level of insulation. Both argon and krypton are found naturally in the air you breathe and are completely harmless.

What are jambs?

Jambs are framing members used to support the window in the wall. Those framing members on the side are, logically enough, called side jambs. The framing member at the top is a head jamb. There are no jambs at the bottom. This framing member is referred to as a sill.

What are mullions?

Mullions are vertical members between window units. They are sometimes confused with mountings, which are secondary framing members that hold multiple panes of glass in the sash. Other parts of the sash include stiles (the outside vertical members) and rails (the top and bottom horizontal members).

How important is weather-stripping?

Very. Weather-stripping is important because it provides the barrier against air and water in windows and doors. It is the only element of operating windows or doors that make them reasonably air tight. High-quality weather-stripping that’s applied and compressed properly really does improve the insulating performance of windows.

What is an impact-resistant glass window?

Impact-resistant glass has strong laminated glass interlayers. When combined with an exceptionally strong win¬dow frame, this type of window provides homeowners with greater security and protection from storms, flying debris and even the occasional stray golf ball. When struck by something hard and forceful, like a tree branch or softball, the glass resists shattering. In the rare event that an object impacts the glass, the pane may shatter, but it remains held within the frame. This greatly reduces the risk of flying glass, water or debris penetrating into the home.

Who should have impact-resistant glass in their homes?

Homeowners living in coastal areas prone to strong winds and storms, or who live directly on a golf course or in an area where vigorous sports activities take place, should consider impact-resistant glass in their homes. Other homeowners might be interested in the sound reduction and security benefits which impact-resistant glass provides.