Sealed Unit Replacement

Replacing the Glass, Keeping the Window

An insulated glass unit is a component. It sits inside the sash the way a battery sits inside a torch, and on most windows it can be taken out and a new one put back without touching the frame, the hardware or the stucco around the opening.

That is the cheap way out of a fogged window, and it is available far more often than the people quoting whole house replacements would like you to believe.

Working Out Whether Your Sash Allows It

The question is how the glass is held in. A sash with a removable glazing bead, a strip of vinyl or aluminum that snaps or screws into a channel around the perimeter, gives the unit up cleanly. Cut the bedding tape, lift the bead, and the unit comes out.

A sash that was glazed at the factory into a welded vinyl frame with structural silicone is a different proposition. It can be done, but between the labour of cutting the old unit free and the risk of distorting a thin welded corner, the number sometimes lands close enough to a new window that the new window is the better buy. We will say so.

Aluminum sliders from the older tracts around Riverside almost always take a snap-in stop, which is why glass only work on them is usually straightforward. The catch on those is the frame itself, and that is the next check.

What Gets Checked Before Anything Is Ordered

New glass in a wet pocket fails the same way the old glass did, only faster, because you have paid for it twice.

So the glazing pocket gets inspected for standing water. The weep holes at the bottom of the frame get probed, and on Riverside houses they are very often plugged. Stucco slurry from an old patch, three coats of paint from a repaint, or just years of dust driven in on a Santa Ana are all common. Blocked weeps turn the pocket into a bathtub, and the bottom edge of the unit sits in it.

The setting blocks also matter. Those are the small rubber or neoprene pads the glass rests on at the quarter points, and they exist to hold the glass edge up out of any water in the pocket and to stop glass touching metal. Missing or crushed blocks put the edge seal in permanent contact with whatever is sitting in the bottom of the frame.

Getting the Order Right

A sealed unit is not a pane of glass, and ordering one wrong is an expensive way to learn that. The fabricator needs the sight size plus the bite on each edge, the thickness of each lite, the spacer width that gives the correct overall unit thickness for the pocket, and whether the glass is annealed or tempered.

The low-E coating has a surface number, and it is not decorative. In an inland climate like this one the coating belongs on the second surface, the inside face of the outer pane, where it reflects solar heat before it enters the cavity. Put the same coating on surface three and you have built a window better suited to Minnesota.

If the opening is a safety glazing location, glass in or beside a door, close to the floor, or near a tub or shower, the replacement is tempered. Tempered units are made to order, not cut from stock, so plan on a longer wait.

Argon, and What It Is Worth

Most modern units are filled with argon, which conducts heat less readily than air and buys a measurable improvement in the U-factor. It also leaks slowly through any seal, and quickly through a failed one.

We fill with argon on units where it makes sense and we are straight about the limits. It is a real gain, it is not a large one next to the coating, and it is not worth arguing about on a small bathroom window.

When We Say No

If the frame is out of square enough that the sash will not close on its stop, if the sill is rotted or corroded through, or if the sash corners have opened up, new glass is money spent on a window that is going to be replaced anyway inside a couple of years.

That is a whole window conversation, and it is on the other service page. Call (951) 721-2320 and we will look at the one you have.