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My windows have storm windows. I am looking at replacing these windows with new ENERGY STAR qualified windows, but they don’t have a storm window. Does not having a storm window reduce their efficiency?

ENERGY STAR qualified windows are designed with multiple panes of glass and specialty gas fills, which create an even more effective barrier within the window itself.

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As I look at your patio door configurations, what is the difference between the "OXXO" and the "XIIX"? We are wanting to have our patio doors open all the way to one side or the other.

The X Panel signifies an operating panel. This panel can only slide to the left or right and has a handle to open the door on it.

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Window measurements seem confusing. Is a 3050 window 3 feet by 5 feet or 30 inches by 50 inches?

Our measurements for new construction windows are in feet. For example, the 3050 stock size would be 3 ft x 5 ft or 36"x60". The size guides can be found for some of our new construction products on our website.

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What is the difference between Design Pressure, Performance Grade, and Structural Test Pressure

The terms "Design Pressure", "DP," "Performance Grade," "PG," and "Structural Test Pressure," "STP" have in the past been loosely used by some in the field.  This answer will clarify what the differences are between them.

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What's the Difference between U-factor and R-value in Energy Efficient Windows?

The biggest difference between U-factor and R-value is that U-factor measures the rate of heat transfer (or loss) while R-value measures the resistance to heat loss. R-value is a measure of conductivity.

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