If your double or triple-pane window is fogged, cloudy, or drafty, the sealed unit has failed — and the fix is replacing the insulated glass unit, not the whole window. National Glass Charlotte installs factory-sealed replacement units that match your original glass's thickness, coating, and gas fill. Your frames stay, your energy bills drop.
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An insulated glass unit (IGU) is two or three panes sealed together with a spacer bar, filled with inert gas, and sealed at the edges. That seal is the weak point. In Charlotte’s climate — 137 degrees of annual temperature swing, heavy freeze-thaw cycles, 38 inches of snow — the seal expands and contracts until it cracks. Once humid air gets inside, the window fogs. And once it fogs, no cleaning product in the world will fix it.
Here’s the honest breakdown for Charlotte homes:
Rarely used in new installs. Cheap but you'll feel every January draft and pay for it in heating.
The standard for Michigan homes. Two panes with argon gas between them block most heat transfer. Great balance of cost and comfort.
Three panes, two gas-filled chambers. The best insulation, best sound control, and highest efficiency. Worth it if you're replacing a large picture window or a window on a cold north-facing wall.
A microscopic metallic layer that reflects heat. Keeps heat in during winter, blocks solar heat in summer. We match your existing Low-E so the new unit looks identical to the old.
Yes. When you call National Glass Charlotte, we don't just cut a generic piece of glass. We measure the exact dimensions and glass makeup of your failed unit — thickness, number of panes, gas fill, Low-E coating, spacer color, and tint. Then we order a replacement that matches to the millimeter.
Nobody standing in your living room will be able to tell which window was replaced. This matters when one window in a row fails and the rest look fine.
A tech comes to your home, removes the interior stop or trim, and measures the failed unit precisely. We also note the glass makeup and any specialty coatings.
We order the replacement IGU to spec. Most units arrive in a few days.
We set the new unit into your existing frame, seal it, reinstall the stop, and clean up. Your frame, trim, and siding stay untouched.
For most Charlotte homeowners, yes — by a wide margin. Replacing a failed IGU runs a fraction of the cost of a full window replacement, and you keep your original frames, trim, and the look of your home.
Full replacement only makes sense when the frame itself is rotted, warped, or leaking. If your frames are solid and only the glass is fogged, glass replacement is the right call.
We'll inspect your window and give you a straight answer either way.
A failed IGU is a hole in your home's envelope. You're paying to heat and cool air that leaks straight through a fogged, drafty window. Replacing the unit restores the insulating barrier — argon or krypton gas between the panes, plus Low-E coating — and brings your window back to its original efficiency.
For homes with several failed units, the energy savings can pay for the work over time. And you'll finally be able to see out of your windows again.
Call 517-543-2760 for a Free EstimateThe classic sign. Moisture is trapped inside the sealed unit.
The inside surface looks permanently cloudy, no matter how much you clean.
A healthy insulated unit is warm on the inside. If the glass is cold to the touch, the gas fill has leaked out.
The seal isn't just about fog — it's an air and energy barrier.
Charlotte's housing stock spans over a century — from pre-1939 Victorians and Craftsman bungalows near the courthouse square to 1970s ranches to 2000s builds along the I-69 corridor.
The 1970s and 1980s homes are the ones we see most: their original double-pane units are now 40-50 years old and past their seal life. If your home was built in that era and the windows are fogging one by one, we can replace them as they fail — no need to do the whole house at once.
Call National Glass Charlotte today for a free estimate on insulated glass replacement. We'll measure, match, and install — fast.
Call 517-543-2760