How to install retrofit replacement windows

The following is a suggested procedure for installing retrofit replacement windows:

• Check the existing window opening for width and height.  The new window should be approximately ½” smaller in the width and height than the existing window opening.  Before removing the old window, check the size, colour and style of the new replacement window that you will be installing.

• Carefully remove all sashes, stops and hardware from the existing window frame.  Remove all of the existing tracks and cut out any mullions, if necessary.

• Before installing the new replacement window, hammer two nails on each side of the existing window frame.  This provides a temporary stop to secure the new replacement window into the opening. 

• Once the new replacement window is in the opening, level the window horizontally using shims.  Then plumb the window vertically.  This is done using double shims at two or three shimming points, depending on the height of the new replacement window.
  

• Check the level and the operation of the new replacement window.  The gap between the window frame and sash should be even at all times, whether open or closed.  Make sure that the new window closes properly.

• Before screwing you new replacement window in place, double check for plumbness and squareness at several points.  Install a 2 ½” #8 screw on each side of the new window.  Screws should be placed at every shim location on the sides of the window.  Do not put any screws in the sill area of the new window and be sure not to over-tighten them, or you could break through the vinyl walls of the window.  Cover all screws with vinyl screw caps.

• Check the operation of the replacement window and locking mechanism again.  Only if your window is operating properly should you move to the next step, which is insulating.

• Insulating around the new replacement window can be done by packing the void around it with fiberglass of low expansion foam.  First, cut off the shims slightly less than flush with the window, all around, on the interior and exterior.

• When fiberglass insulation is used to insulate around the new replacement window, it should be loosely packed and not forced into the gap.  Forcing insulation in will reduce its efficiency and could bow the window frame.

If foam is used, fill the gap from the inside first, placing the material between the new replacement window and the existing window frame.  Again, be careful not to over-apply.  Repeat the process from the exterior of the window.  Note that it is not necessary to fill the entire cavity with foam.  Each pass should, however, be at least 1” deep.

After the foam is dry, cut off any that may be sticking past the edge of the new replacement window surface using a sharp knife.  Apply caulking at all of the shim locations around the new replacement window.  Do this on the inside and outside of the new window.  You are now ready to trim your new replacement window on the inside and flash (or cap) it on the exterior.  Capping a retrofit replacement window is an art and not easily done by the layman, so we ill discuss it in detail in another article.