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What Causes Discoloration in Double-Pane Windows?

Double-pane windows help you save on your utility bills by helping reduce heat transmission between its indoor and outdoor surfaces. It’s uncommon, but sometimes double-pane glass may have discoloration. So, what causes glass discoloration, and how it can be prevented?

How Do Double-Pane Windows Work?

To understand how discoloration happens on double-pane windows, let us first discuss how it works as a part of the energy envelope. Every type of occupied building has an insulated enclosure that consists of the roof, exterior walls and fenestrations (skylights, entry doors and windows). These components comprise the energy envelope, which helps maintain consistent indoor temperatures. This results in lower indoor heating and cooling requirements, reducing air conditioning system output, which, in turn, can result in energy savings.

Insulation can be added to the attic and exterior walls in the form of batt, foam or blown-in insulation. Window frames can be insulated with a foam core or chambered construction. Window glass, on the other hand, needs a different type of insulation as the aforementioned insulation types are opaque. Glass also happens to be naturally conductive, which means single-pane glass is out of the equation.

The solution is double-pane glass. Separating the interior and exterior surfaces with a vacuum airspace slows down heat conduction and complements the other parts of the energy envelope. Double-pane glass has proven to be so effective that our replacement windows and patio doors feature double-pane High Performance™ Low-E4® glass as a standard feature.

Preventing Double-Pane Window Discoloration

Discoloration on double-pane windows is typically caused by indoor moisture and can appear as dark-colored streaks on the glass surface. This happens when moisture infiltrates the airspace between the glass panels. It’s not soot or dust, and it won’t come off when you try to clean the windows. Depending on the type of glass, it may be covered by your replacement window warranty.

The good news is, discoloration is preventable. You need to set your humidifier/dehumidifier system to maintain relative indoor humidity. Discoloration is a slow process, and you might not notice it happening until it’s too late.

Renewal by Andersen® of Wyoming is your leading provider of replacement windows as well as hinged and sliding patio doors. Give us a call at (307) 472-2199. You can also fill out our contact form to schedule an appointment. We serve customers in Laramie and Cheyenne, WY.


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