Angie's LIST Guide to
Replacement windows

When to replace home windows

Depending on the material, if you live in an older home and your home’s windows are at least 15 to 30 years old, you may be noticing signs of increased wear and tear and thinking about replacing them.

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• Windows are unattractive: faded, worn or appear outdated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 upwards 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.

Upgrading your home’s overall energy efficiency is a common reason for installing 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 continue to increase year over year, installing new windows can be one step towards improved efficiency. Homeowners who replace single-pane windows with energy efficient windows will immediately notice a significant reduction in their heating and cooling bills.

While certain smaller steps can be taken to mitigate energy loss from inefficient windows, including repairing ill-fitting sashes and frames, adding spray foam or caulk to fill in voids or holes, and installing plastic wrap during colder months, installing modern highly energy-efficient windows can help you do an end-run around high utility bills.

Another selling point that may attract many homeowners to replacing their home's windows is ease of cleaning. Features like tilt-out sashes in double-hung windows can make routine window cleaning much more convenient.

Cost vs. value of new windows

If you’re thinking replacing windows to add to your home’s overall resale value, it’s an investment you should consider carefully, as it’s significantly expensive – especially for the most energy efficient windows. For the average-sized U.S. home, installing an entire set of all brand-new windows can easily cost more than $10,000 total.

It’s important to note that many homeowners consider replacing windows to add to their home’s resale value. While few, if any, home improvement investments net a positive return, homeowners who install new windows can reasonably 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 one subject to HOA covenants? If you’re thinking about replacing your home’s windows that should be one of the first questions you answer. If you live in a historic district that restricts or prohibits changes or alterations to a home’s historical exterior, you may be bound by covenants that can prevent you from installing new windows.

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

If you’re unable to change your windows, many window companies and other contractors may be able to restore older windows to a like-new appearance – and often at much lower cost than window replacement.  If you live in particularly older home with historic windows, consider hiring a window restoration specialist to improve and preserve the windows.

One of the biggest reasons to replace your home's windows is to improve the overall energy efficiency of your home. But how do you compare the energy efficiency among differing window products? Look at the labels.

Windows that feature an Energy Star label have passed standards tests that prove that the products meet minimum criteria for energy efficiency. Energy Star-rated products typically cost more than traditional products, but also offer great energy savings in reduced 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 non-profit 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 Council, window products that carry the NFRC label have been tested to ensure that their advertised energy-efficiency claims are accurate.

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 number between 0 and 1, the lower a window’s SHGC rating, the more heat from sunlight 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 will also 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 fall into a range between 0.1 and 0.3, with lower numbers indicating reduced air leakage. Including 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 insulated 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 such as argon or krypton rather than just air. These gases are inert, meaning that they do no react to contact with other substances. They also offer better thermal resistance than air, which provides great insulating properties and therefore better energy efficiency.