Broken Window Seals

I recently polled my 8,000+ member Facebook Group and found that 88% of inspector members find at least 1 home per week with broken window seals.

Broken window seals are common all over the US, and the condition is challenging to all window manufacturers.

The first step when repairing/replacing a broken window seal…check the warranty.

Most manufacturers offer a guarantee against insulated glass failure. The warranty period varies from a limited period to the lifetime of the window; however, a range from 10 to 20 years is typical.

The weather, poor manufacturing practices, product age, and cleaning chemicals (acidic solvents) are common reasons window seals fail.

Sunshine is the most common cause, which is why south and west-facing windows usually fail first.

A condition known as “solar pumping” hardens the sealant that forms the seals of the window. When sunshine hits a double pane window, the air inside heats, causing the sealed window unit to expand, pushing air out through the semi-permeable seals located at the edge of the glass. Later in the evening, the window cools and contracts, drawing air and humidity into the window pane’s gap.

Silica pellets, a hygroscopic substance used as a drying agent (desiccant), are placed inside the aluminum perimeter strip (called the spacer bar). The pellets absorb moisture.

Droplets form on a failed double pane aluminum clad window.

When the seal fails, as it will over time, moisture-containing air infiltrates the space between the panes causing the silica desiccant to become saturated. At this point, condensation will begin to form along the perimeter of the window. Desiccant has a limited capacity and lifespan — how limited depends on the quality of the desiccant itself and the windows’ framing material.

Day after day, year after year, the cyclical expansion and contraction stress the window seal, fills the air space with moisture, and overloads the desiccant.  

The EWC – Efficient Windows Collaborative says:

The durability of insulating glass (IG) units is critical to window energy performance. Seal failure leads to the loss of insulating gas and can result in condensation from moisture penetrating the panes, which can degrade low-E coatings.

Window Durability

ENERGY STAR® is the government-backed symbol for energy efficiency, providing simple, credible, and unbiased information that consumers and businesses rely on to make well-informed decisions.

Before a window manufacturer can earn the ENERGY STAR certification, the product must undergo special tests.

From July 2010 on, to minimize the likelihood of seal failure and gas loss, insulating glass in ENERGY STAR windows must be certified through recognized programs. IG certification requires that sample IG units undergo accelerated weathering over extended periods to determine whether the IG unit can withstand extreme temperature swings, high humidity, and UV radiation without failure. IG certification also requires that the manufacturer implements in-house quality assurance. Most manufacturers offer a warranty against insulating glass failure, which varies from a limited period to the window’s lifetime. A range from 10 to 20 years is typical.

Window Durability

Weather Shield Says

If you live in a climate with extreme temperatures or high humidity, replacing the window may be your best bet. Environments with high humidity levels will often leave windows with broken seals with constant condensation, ruining the window’s aesthetic nature and diminishing the view. In climate zones with extreme temperatures—hot or cold—you will see more benefits from replacing the window with a new one. The insulated glass will protect your home from hot and cold spots, keeping your home more comfortable and reducing energy bills. The protection is essential in small rooms with only one window. A broken window seal in these rooms can result in uncomfortable conditions when it is very hot or cold outside.

Weather Shield: With more than 1,900 employees we offer comprehensive products and services nationwide.

Over the years, Pella has built a reputation for creating innovative quality products and recommends checking the window manufacturer’s warranty.

If you can’t find a name or other means of identification embossed, stamped, or otherwise marked on the window, you will be at a disadvantage when attempting to contact the manufacturer.

If you’re buying new construction or remodeling your home, ask the builder or window representative for the manufacturer’s name and warranty information.

I provide New Construction Coaching
Pella demonstrates the process of heat/humidity and UV testing.

Eventually, fogging may develop between the panes of an insulating glass product. Given enough time, the seals between the panes will break down and allow moisture to enter. The desiccant material will attract and hold as much moisture as possible but will eventually become saturated. When that happens, fogging will occur. Exactly how long this will take depends on the actual environmental conditions, the sealing and desiccant materials used, the design of the insulating glass, the overall design of the window, and a host of other factors too numerous to mention here. However, nothing lasts forever.

Check the manufacturer’s warranty to understand what it does and does not cover thoroughly. Most Pella product warranties provide at least 20 years of coverage on the glass.


Understanding the manufacturer’s warranty starts with identifying the window company.

The easiest way to identify a window is by locating the manufacturer’s name directly on the product? Acron, Biltbest, Caradco, Hurd, Marvin, Malta, Oldach,  and others stamp their name on the window hardware – generally on the handles, sash locks, or other window or door hardware.

Look carefully inside the insulated glass, between the panes. You may find information embossed directly onto the spacer bar.

Companies like Andersen, Pella, Better-Bilt, Shelter, Outlook, and Windsor will have their names “etched” in the corner of the glass; other companies like Crestline, SNE, and Vetter are all known not to place their names on units, anywhere…instead, they use a string of letters and numbers on their products. Unless you know exactly what these letters and numbers mean, you’ll have difficulty identifying the manufacturer.

My Advice

If there is no warranty protection on the window, you’ll need to replace the insulated glass unit within the frame. Depending on the make/style, a maintenance specialist will remove the window stop and replace the glass. Very seldom does a failed window seal result in the replacement of the entire window frame.

Don’t be fooled. You can’t seal a window by drilling a hole in the glass. A method called “defogging” doesn’t address the root cause of the failure (a broken window seal), and the “quick fix” seldom includes a repair warranty. Other gimmicks include cheap products sold at big box stores. They are a waste of money.

My best advice is to remove and replace the window and leave the job to a glass replacement professional. Look to spend between $100 – $250 per window. I recommend this local (metro Jackson, MS) window replacement company and other trusted professionals here.

Join my 9,000+ member Facebook group for homeowners and inspectors.

Click to Read Comments!

Loading Facebook Comments ...

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Black and White Premium WordPress Theme