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Window Installation: How to Install Replacement Windows

New, vinyl replacement windows are low-maintenance, offer energy-efficient features and operate smoothly for years.

Replacement window.

Tools & Materials

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Measure for the New Window

How to measure a window.

It's important to have accurate measurements for every window in your home. Accurate measurements ensure that your windows fit properly for maximum energy savings and easy installation.

Good to Know

Take all measurements from inside your home. Using the smallest measurements ensures that the replacement window will fit inside the existing window frame.

Step 1

To find the width, measure from the inside of the jamb on one side of the window to the inside of the jamb on the other side of the window. Measure at the bottom, middle and top of the window. Use the narrowest measurement for the width of your replacement window.

Step 2

To find the height, measure from the top of the sill to the bottom of the window's head jamb. Measure at the left, middle and right of the window. Use the shortest measurement for the height of your replacement window.

Remove the Old Window Sashes

Remove old windows.

Since the replacement windows fit inside the existing window frame, you only have to remove the sashes, parting bead and inside stop from the existing window. To make the project easier and safer, install your new windows from inside your home.

Step 1

Remove the inside stop pieces from the window. Take care when removing these pieces; you'll reuse them when installing the new windows.

Step 2

Remove the inside sash. If the old window uses weights, cut the sash cords or chains. Let the weights fall to the bottom of their wells, and simply leave them there.

Step 3

Slide the outside sash to the bottom of the window. Remove and discard the parting beads. Remove the outside sash in the same manner as the inside sash. Don't remove the exterior stop from the window jambs. These stops will retain the replacement window when you install it.

Step 4

Clean the window jambs and sill thoroughly. If the old window had weights, either drive the pulleys into the frame or remove them entirely. Fill any holes in the jambs or sill with caulk.

Install the New Window

Install new window.

Poorly installed or adjusted windows waste energy and are difficult to operate, so take your time installing and adjusting your new window.

Good to Know

Energy-efficient windows and doors not only help retain comfortable air temperatures inside, but they can also help with appropriate moisture control and reduce the level of noise coming from outdoors.

Step 1

Lay a bead of caulk along the inside of the outside stops on the jambs. Mark the sill for the sill angle. Caulk and install the sill angle.

Step 2

Center the top and bottom sashes vertically in the new window frame. Slide the bumper stops toward the center of the frame until the four mounting holes in the side jambs (two top and two bottom) are visible.

Step 3

Place the header, also called the expander, on top of the window and caulk its top.

Step 4

Place the window in the opening and check for square. If the window isn't square in the opening, shim as needed to square it. Install the mounting screws at the top and bottom of each side jamb. Don't install the screws so tightly that they deform the side jambs.

Step 5

Slide the header up so that it seals any gap between the top of the new window and the old frame.

Step 6

Slide the top and bottom sashes up and down to check for gaps and smooth operation. If the sashes don't operate smoothly, use the built-in adjustment screws in the side jambs to adjust the window frame. Precise adjustment varies by manufacturer, so refer to the manufacturer's notes for specific adjustment instructions.

Step 7

Caulk the inside of the window and reinstall the inside stops.