A: The two most common window issues we see are (1) drafty windows and (2) foggy windows or also known as seal failures.
Today we are going to talk about foggy windows. Let me paint a scenario for you. You wake up in the morning and notice one of your double-pane windows looks a little foggy. You wipe it off between eating your breakfast, maybe with the sleeve of your pajamas and it’s still cloudy.
Perplexed, you try and you open your window (if it’s not jammed shut) to clear the fog, but still the fog remains. Suddenly you realize, Houston…we have a problem! So what’s going on? The foggy glass is actually coming from within the two panes of glass.
While some condensation is normal; it’s not normal when it doesn’t go away. What you need to know is that fogged glass is not only unsightly as you can’t see clearly out your window, but it means that your window is not working properly anymore and is costing you money. Imagine money literally flying out your window!
So What Happened?
The insulating factor in the glass has been compromised. Glass all by itself is a horrible insulator. A single-pane window has an R-Factor (the ability to stop the flow of heat) of 1 where a standard insulating glass unit has an R-Factor of about 2. It’s important to know that the R-Factor is greater not because of the two panes of glass but because there is space in between the two panes.
Want to increase your R-Factor up to 7 or more? You can add argon or krypton gas and low-E coatings between the panes! But if you want to know how efficient an entire window is rather just the glass itself, you need to know the U-Value which is the only recognized rating in window efficiency by the NFRC (National Fenestration Rating Counsel).
To be Energy Star rated in MA the window needs to have a U-Value of .32 or lower. For government rebates, the U-Value needs to be .30 or lower. At Coastal Windows & Exteriors, our most efficient window is .14.
One Seal vs Two Seals and Spacers
- Most high-quality double-pane windows have two perimeter seals.
- The inner seal is manufactured to resist water, aging, and corrosion, and the outer seal adds strength.
- Once one seal fails, the second seal will only last so long until it too fails. It’s also important to note that some window manufacturers only make windows with one seal. Winter Tip: Don’t buy windows with one seal.
- Typical seals also include a hollow spacer to keep the panes rigidly spaced with a small bead of moisture-absorbing desiccant to prevent windows from fogging up. If a small amount of moisture infiltrates the seal, the desiccant becomes saturated and thus my dear Watson moist air starts entering and you have a foggy window or seal failure. A warm-edge spacer lowers the conduction and keeps your home warmer. Winter Tip: Buy windows with warm edge spacers.
What You May Not Know
- Typical home inspections exclude the identification of failed seals on insulated glass. Why you ask?
- When a seal failure happens you will see 3 things: nothing (initial stage because the desiccant is doing its job for the most part), condensation, or foggy glass. So it’s entirely possible that a home inspector could miss one of these signs. Your custom-made windows are made by the manufacturer to a specific size then set into a site-built frame by contractors or you. If they are not installed correctly or they aren’t properly caulked where the seal meets the stops, they can be at risk for seal failure. Check your warranty to make sure it’s not dependent on who installed your windows.
- When screens are present or you just have really dirty windows, the seal failure isn’t as easily detected.
What You Should Do
- Examine your windows and frames at the beginning of each season. Yep, this means you need to clean them.
- You can protect your double-pane windows by preventing excess moisture from forming by creating good air circulation.
You can determine if a window is covered under warranty by looking at the inside top or bottom of the window for a sticker which should include the manufacturer name so you can determine whether a failed glass unit is still under warranty. There are many warranties out there from a few years to lifetime.
Your best defense against seal failures is to buy a window with a lifetime warranty. If you think you may have seal failures, but aren’t sure, please give us a call at 978-304-0495 and we will check out your windows free of charge. We’re here to help keep you comfortable no matter the season.