You've seen the fog between your window panes. You've noticed a suspicious drip after a hard rain. Maybe you've never given your old sliding glass door a second thought … until now.
In this episode of Glazed & Confused, Duncan tackles three of the most common questions homeowners ask, and the answers are more nuanced (and in one case, more alarming) than you might expect.
Why Is There Condensation in My Window?
This one depends entirely on what kind of window you have — and the answer splits into two very different problems.
If you have single-pane windows, condensation on the inside of the glass is essentially unavoidable. A single pane of glass in an aluminum frame offers almost no thermal barrier. When warm, moist indoor air meets that cold surface overnight, condensation forms. The fix? Energy-efficient dual-pane windows. There's no workaround here.
If you already have dual-pane windows and you're seeing fog or moisture between the two panes, that's a seal failure — and the cause depends on the window's age.
Older aluminum-framed dual-pane windows from 20–30 years ago used what's called a “Christmas tree gasket” — a rubber seal designed to hold the glass in place. Over years of opening and closing, the sharp glass corners gradually cut through that rubber, breaking the hermetic seal. At that point, replacement of the entire window makes more sense than repair — putting money into those old frames is throwing it away.
Newer vinyl dual-pane windows with a failed seal are a different story. In many cases, you can replace just the glass unit — called the insulated glass unit (IGU) — rather than the whole window. It's less expensive, though it typically comes with a shorter warranty than a full window replacement.
The bottom line: Every situation is unique, and a good window company can tell you whether you're looking at a glass swap or a full replacement. Don't assume the worst until you've had it assessed.
Why Do My New Windows Leak When It Rains?
This is a surprisingly common issue — and one of the more frustrating ones, because it often has nothing to do with the window itself.
The most common culprit is original installation error. When a home is built, the window framing requires proper flashing — a layered system of moisture barriers that directs water away from the structure. When that flashing is installed incorrectly (with the tar paper in the wrong order, for instance), rainwater that penetrates the stucco — and stucco is porous, it's meant to drain — ends up traveling behind the moisture barrier instead of over it and down the wall. The result: water intrusion that looks like a window leak but is actually a construction defect. Critically, installing a new replacement window will not fix this problem. The underlying flashing has to be corrected.
If you already have replacement windows and they're leaking, the more likely cause is caulk separation — the seal between the new window frame and your wall surface (stucco, wood siding, trim) has broken down. This is a much simpler fix, but it needs to be caught before moisture works its way deeper into the wall assembly.
The unsettling reality: improper installation can sit hidden behind your walls for years, only revealing itself after an unusually heavy rainstorm. If you're seeing persistent leaks around windows in an older home, it's worth having a professional assess the flashing, not just the window.
Are Sliding Glass Doors Easy to Break Into?
Here's the one that might keep you up at night.
Modern sliding glass doors are very secure. The glass is substantially thicker than older versions, locking mechanisms are robust, strike plates are anchored with three-inch screws rather than three-quarter-inch screws, and the best locks engage in both directions — preventing the door from being jimmied up or down.
Old sliding glass doors, however, are a different story entirely.
In the 1960s and 70s, some manufacturers produced aluminum sliding doors in what can only be described as the wrong configuration: the sliding panel sat on the outside of the track rather than the inside. That means the fixed panel is on the interior of your home, and the sliding panel is exposed on the exterior. With that setup, anyone with a crowbar or even a flathead screwdriver can slip it under the sliding panel, lift it up, and remove it from the track entirely. No forced entry. No broken glass. Just gone.
The locks on those doors weren't much better — small metal catches that offered minimal resistance to anyone determined to get through.
Tens of thousands of these doors are still installed in homes today.
How to check: Look at your sliding glass door and identify which panel moves. If the sliding panel is on the exterior side of the track (meaning someone outside could access the bottom of it), that's a serious security vulnerability worth addressing immediately.
If you're not sure, it's worth a call to a window and door professional for a quick assessment. Upgrading to a modern sliding door isn't just about aesthetics — it's a legitimate safety upgrade.
The Takeaway
Windows and doors are easy to ignore until something goes wrong. But as this episode makes clear, the problems often run deeper than they appear — and the solutions are more varied than a simple “replace it or don't.” Whether you're dealing with foggy glass, mysterious leaks, or a door that's been quietly unsecured for decades, the first step is always getting the right diagnosis.
Have a question for Glazed & Confused? Visit newmanwindows.com/stay-glassy, scroll to the bottom, and submit your question. You might be featured in the next episode.
