Replacing windows saves energy

If you live in an older home and the windows are at least 15 to 30 years old, you should consider replacing them. for any of the following reasons .

Common reasons to replace older windows:

Poor window energy efficiency

Windows are unattractive — faded, worn or appear outdated

Windows are bowed, sagging or bent, creating pockets of air infiltration

Windows leak during rainfall

Windows accumulate condensation or frost between panes

According to a 2007 study published by the National Association of Home Builders, aluminum windows are expected to last between 15 and 20 years, while wooden windows should last upward of 30 years. Since they’re considered more durable than wood or metal windows, vinyl and fiberglass windows may last even longer. If your home’s windows are 15 to 30 years old or more, you may be experiencing some of the conditions noted above.

Improving your home’s energy efficiency is a good reason to install new windows. According to the U.S. Department of Energy, heat loss from inefficient windows can account for 10 to 25 percent of your home’s heating bills.

If your home’s heating or cooling bills are too high and increase every year, installing new windows can improve efficiency. Replacing single-pane windows with energy-efficient windows will dramaticaly lower heating and cooling bills.

Smaller steps can be taken to mitigate energy loss from inefficient windows such as repairing ill-fitting sashes and frames, filling voids or holes with spray foam or caulk, and installing plastic wrap during colder months.

New windows are easier to clean. Features like tilt-out sashes in double-hung windows can make routine window cleaning more convenient.

Video: Replace Windows

Cost vs. value of new windows

Replacing your home's windows to improve its overall resale value is an investment to consider carefully. For the average-sized U.S. home, installing an entire set of brand-new windows can easily cost more than $10,000. Homeowners can expect to recoup about 60 percent of that investment in terms of improving their home’s overall resale value.

Historical or homeowners association considerations

Is your home in a historic district or subject to homeowners association covenants? If you live in a historic district that restricts or prohibits changes or alterations to a home’s exterior, you may be bound by covenants that prevent you from installing new windows.

Since a new window installation will alter the aesthetic of your home’s exterior, HOAs may have regulatory control of installing new windows. While an HOA’s policies or bylaws might not strictly prohibit window replacement, it may limit your choices of window styles, colors or patterns.

If you’re restricted from changing your windows, window companies and contractors can restore older windows to look brand new and cost less than window replacements. If your home has historic windows, hire a window restoration specialist to improve and preserve them.

When dealing with windows on old homes, local historical societies may have regulations about replacement windows. (Photo by William Coffee)

Window types and materials

Not all windows are created equal. If you're replacing your home's older windows with identical new ones, what style of window you choose might not matter much. However, if you want to change the configuration, appearance or function of your windows, take a look at some of the most common window styles available.

Horizontal sliders or gliders

Horizontal sliders feature sashes that open and close by sliding back and forth horizontally on a track within the window frame. Only one side of the window can be open at a time.

Double hung

This is probably the most popular and easily recognizable window system in American homes. It features two sashes, panes of glass suspended in frames, that overlap slightly and move vertically in the window frame (although most models feature a fixed upper sash). The sashes easily move up and down due to counterweights on pulleys or springs hidden in the window frame.


Awning windows are hinged at the top, allowing them to open outward from the top, which gives them an appearance similar to an awning.


Hopper windows are hinged at the bottom, allowing them to open outward from the bottom, which gives them an appearance similar to old-fashioned coal furnace chute hoppers.


Casement windows typically feature interior mounted opening mechanisms that allow the window to open outward along a vertical hinge, similar to the way a door opens. In most modern American homes, a casement window opens via cranked handle.

Bay or bow windows

Bay or bow windows are typically made of a framed structure featuring windows that protrude from the exterior of a home. Popular in late 1800s architecture, a bay or bow window can provide a few more square feet of living space to a room, creating the illusion of a much bigger space.

Fixed windows

A fixed window is a window that cannot be opened and is mainly used to allow light to enter a home.

Windows can be built from wood and other materials, and each has benefits and disadvantages.


One of the oldest building materials available, new all-wood windows naturally resist transferring heat or cold, but swell with humidity changes. Wood requires more maintenance (regular painting or staining) than other materials. They are often more expensive.

Clad wood

Windows with clad construction have wooden interior frames sheathed in a durable exterior material like vinyl or aluminum.  


Fiberglass windows are durable and have greater heat transfer resistance than wood or vinyl frames, according to the U.S Department of Energy’s Energy Savers program.

Aluminum or metal

Aluminum or metal frames are durable, strong and virtually maintenance free. However, because metal conducts heat and cold quickly, metal windows are a poor choice for upgrading a home’s energy efficiency.

Vinyl or PVC

A popular window choice is vinyl or PVC. They are highly durable and don’t require regular painting. Some vinyl window frames offer insulated cavities, which can increase your home’s energy efficiency.

Window energy efficiency

One of the biggest reasons to replace your home's windows is to improve energy efficiency. Compare the energy efficiency among window products by reading the labels.

Windows that feature an Energy Star label have passed standards testing that prove the products meet minimum criteria for energy efficiency. Energy Star-rated products cost more than traditional products, but can reduce your utility bills. For more information on how window products qualify for the Energy Star label, visit the Energy Star website.

Another energy efficiency indicator on new window products is a label from the National Fenestration Rating Council (NFRC). The NFRC is a nonprofit organization that independently assesses and issues energy ratings for window products.

NFRC’s testing of window energy performance is also a key component of Energy Star ratings. According to the NFRC, window products that carry the NFRC label have been tested to ensure that their advertised energy-efficiency claims are accurate.

Fixed windows don't open, but are often large to provide plenty of natural light.. (Photo by Katelin Kinney)

Window energy efficiency terms

NFRC labels carry important information about a window’s energy performance, which are expressed in two primary efficiency measures.

1. Solar heat gain co-efficient (SHGC)

SHGC indicates how much heat from sunlight a window can block. Expressed as a number between 0 and 1, the lower a window’s SHGC rating, the more sunlight heat it can block. For instance, a window with a SHGC of 0.35 will allow more heat to pass through the window than a product with a SHGC of 0.27.

2. U-factor

A window’s U-factor is a measure of how much heat can escape a home by passing through the window.  A window’s U-factor typically refers to the overall insulating properties of the window. Much like SHGC, U-factors occur on a scale between 0 and 1 — the lower the number, the better insulation performance a window can provide. For instance, a window with a U-factor of 0.15 offers more insulating properties than a window with a U-factor of 0.30.

Some NRFC labels carry additional supporting information about a replacement window's performance.

3. Visible transmittance (VT)

VT refers to how much visible light a window product transmits. Like other window ratings, it’s expressed as a number between 0 and 1. The higher the VT rating, the more visible light the window allows to pass through. So a window with VT rating of 0.50 permits much less light transmittance than a window with a VT rating of 0.75.

4. Air leakage

This rating refers to how much air infiltration a window product permits. According to the NFRC, air leakage standards typically range between 0.1 and 0.3, with lower numbers indicating reduced air leakage. An air-leakage rating is optional for manufacturers.

Window efficiency features

Some of the following features, taken alone or used together, can help a window product achieve greater energy efficiency by lowering SHGC or U-factor values.

1. Low-emissivity or low-E coatings

Low-E windows feature a special coating on the window pane glass that reduces heat transfer, meaning it can prevent heat from entering a home in warm climates or prevent heat from leaving a home through a window in cooler climates. According to the U.S. Dept. of Energy, windows that feature low-E coatings cost 10 to 15 percent more than non-coated windows on average.

2. Insulated windows

Insulated windows feature more than one pane of glass to provide a layer of insulation between the panes. Usually available in double- or triple-pane configurations, the sealed layer or layers of air or gas between the panes helps prevent heat transfer or escape.

3. Gas-filled windows

Some manufacturers offer insulated windows that are filled with gases like argon or krypton instead of air. These gases are inert, and don't react to other substances. They also offer better thermal resistance than air, resulting in greater insulation and improved energy efficiency.

Choosing a window contractor

Because replacing your home’s windows is such a large investment, it’s important to select a replacement window contactor with care. Costs vary widely depending on energy efficiency, material and style. Get at least three contractors' estimates before you choose a contractor.

Ask for references and take the time to check them. If a replacement window contractor has done a number of installations in your area, visit a recent job site to view the quality of their installation. Verify that the contractor has the necessary license if required and ask for proof of insurance or bonding.

Window contractors might be certified by manufacturers to install or perform warranty work on window products. If you want to purchase a particular manufacturer or brand of windows, ask your potential contractors if they've undertaken any manufacturer's training or certifications.

It's also a good idea to plan window replacement for a relatively mild month of the year. Although most professional window installers can finish their work in a few days or a week, planning the project for warmer weather can help you avoid being stranded in a house without windows in the middle of winter.

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