What Is the Right Size for a Double Casement Window?

Measurement

• Your first step when determining the right size for a double casement window is measuring the window frame. Correct sizing (usually accuracy to 1/16 of an inch) will help you avoid purchasing an unusable and possible nonreturnable window. Remove the old caulking and interior casing to get an accurate measurement of the window opening Measure the width and height outside the frame for new windows. If you are replacing an existing double casement window, measure the opening within the current frame. Your manufacturer will advise whether you need to adjust your measurements based on window design.

Considerations

• Not all windows in your home will be the same size. Note the number of windows you need to replace and calculate the measurement for each separately. Open windows to get a more accurate measurement of the area inside the framing. Also, look out for any rot or deterioration around the window frame that may affect installation. Significant damage to an existing frame may require installation of a full frame replacement window. Brickwork and other trim near the window opening may also affect sizing.

Benefits

• Small double casement windows provide better air infiltration and circulation compared with larger sliding or hanging windows. Though you will receive less egress and light, casement windows are a better choice for adequate ventilation if you have a small window openings. The U.S. Department of Energy states that casement and awning windows provide the maximum and most effective ventilation in homes.

  Double casement windows also trump sliding and double-hung windows when it comes to air leakage and insulation. Features such as double glazing and air tight seals in double casement windows help retain heat and improve energy efficiency. Since double casement windows possess a high R-value — the measurement of protection against heat loss through glass areas — you can build large window openings without sacrificing energy efficiency or comfort.

Features

• The size of your double casement windows should account for additional features that help with insulation and prevent air leakage. For example, weatherstripping acts as the seal between the window frame and sash. It also is the most vulnerable area of your window and can suffer significant wear and tear. Measure the width and depth of the gap where weatherstripping will be located to ensure correct installation and durability during frequent use.