How Do You Install Double-Glazed Windows?

Double-Glazed windowsIn addressing the question of how to install double-glazed windows, it is important to first define what a double-glazed window is and to explain briefly why anyone would choose this particular kind of window. Double-glazing, also known as insulated glazing, refers to using two panes of window glass in each window and coating them with a protective film. This thin film is normally made of some form of metal and will inhibit the transfer of heat through the glass. Either a gas or a vacuum is placed between the two window panes to further enhance insulation capabilities. The motive for installing double-glazed windows may be to lower energy bills, reduce condensation, increase security levels, or to effect noise reduction. There are particular varieties of double-glazed windows that excel at each of these functions, acceding to Double Glazing Info. As to actually installing a double-glazed window, the process is largely the same as for other types of windows, though a few differences exist.

Prepare for the Task

Before installing, and before purchasing, your new window, you must carefully measure the dimensions of the window opening. You can simply measure the old window, if one is present, but if you take your measurements directly off the opening, be sure to allow a about a quarter inch play.

Make sure that a lintel runs above your window opening if you use uPVC since such windows do not bear loads. Double and triple check the sizing, and make sure you have no doubts about which side of the window is to face inward and which face outward. Gather all tools you will need, including drill and drill bits, power saw, bubble level, chisel, screwdriver, frame sealant, and hammer. Clear away curtains, blinds, and decorations, and lay down a tarp to collect the debris.

Remove the Existing Window

First of all, remove the old window’s openers and moving sashes. A screwdriver and a pry bar should be all you will need to do this. Next, beginning at the top corner, carefully pry the glass away from the frame. Use a utility knife to cut through any caulk, plaster, or grout that is clinging to the window frame.

Now you are ready to saw through the frame and remove it. Cut the vertical frame posts with the saw at an angle, but do not cut quite all the way through since you might damage the adjoining wall. Pry up the frame with a chisel to get in a good position to finish cutting all the way through. Now you can simply pull the framing apart. Just be careful not to let it fall on you or onto the floor boards. In like manner, cut and pull out the sill and all other components of the old window. Clean off the debris, and smooth the surface of the inner opening in preparation for the new window.

Fit the New Frame

The first step in the installation of double-glazed windows is to lay down the sill piece flat. It must be leveled, nailed, and cemented into place. If being laid down on brick, fixing bolts must be used. The sill’s end caps should be caulked or super-glued on.

Next, remove all glazing beads and mark their positions so you can replace them later. Now you can lay the window down on the sill and slowly maneuver it into position. You want a relatively tight fit, but shims can be used if necessary. Check for level in the following order: top, bottom, sides. Check for square by measuring diagonally both ways and then comparing results- they should match. Now drill holes and insert screws. If the frame is wooden, you may want to use nails instead. You must also screw or nail the frame to the sill. Do not over-tighten the sill or the frame pieces since this could lead to warping.

Finish the Job

If you want to fully know how to install double-glazed windows, the final steps must also be given attention.

  • Insert glazing bridges in the frame recess.
  • Position the glass to a centralized location using glazing packers.
  • Reattach the glazing beads in this order: top, bottom, then sides.
  • Apply caulk or frame sealant wherever the frame meets the wall, both inside and outside of the house.
  • Fully insulate the window’s perimeter.
  • Install any trim that will go around the window.
  • Attach any handles or locks according to the manufacturer’s instructions.
  • Remove protective tape, clean the window, and touch up any damage to paint or drywall surrounding your new window.

Once all of the above is competed, wait a few hours before opening the window. The sealants need time to set.


If you are interested in learning how to install double-glazed windows, the above-given steps give a general outline of the task. You should not begin until you are sure you can complete the job from beginning to end, but if necessary, you could tarp over the window opening until you are able to finish. The benefits of installing double-glazed are many, and the procedure is relatively simple for those with basic home improvement skills.

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