Window Glass Replacement in Portland and Southern Maine

When the frame is sound and only the glass has failed, a new sealed unit costs a fraction of a new window. Here is how to tell which you need, and what the code says about the glass that goes back.

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Cumberland, York & Sagadahoc64 cities & counties

Double-pane windows from the 1980s and 1990s are now thirty or forty years old, and a lot of the glass calls we get here are about one symptom: a milky film or droplets between the two panes that no amount of cleaning removes. That is a failed seal. The insulating gas is gone and moist air has gotten in. It does not mean the whole window has failed.

Older houses bring the other kind of glass work: single panes in wood sash, held by putty that has dried and fallen out. Both can usually be fixed without a new window, and this page covers how, when it is not worth it, and the safety glass rules that decide what goes back in.

Telling a failed seal from a wet room

Where the water sits tells you what is wrong:

Between the panes: the sealed unit has failed. It will not get better, and in cold weather the fog comes and goes with the sun.
On the room side of the glass: the indoor air is too humid for the outdoor temperature. A new sealed unit with a warmer inner pane helps, but kitchen and bath fans, and a humidistat if there is one, matter more.
On the outside of the glass on a clear morning: a sign of a very well-insulated unit, not a defect.

Look at the frame next. If the sash is square, the frame is dry and the window opens and locks, new glass is usually the right repair. If the bottom rail is soft, the frame is warped, or the window leaks air all around, the glass is the least of its problems and replacement is worth pricing.

How a sealed unit gets replaced

Most double-pane windows hold their glass in a sash with removable glazing stops or a snap-in bead. The job goes like this:

We measure the old unit and read the spacer for any code or date; the new unit is built to size, so there is a wait of days to a few weeks.
On the day, the stops come off, the old unit is cut free of its glazing tape or sealant and lifted out.
The sash rabbet is cleaned and checked for rot, new setting blocks go in so the glass sits off the bottom, and the new unit is set in fresh glazing tape or sealant.
The stops go back, and the window is checked for operation and drainage.

Some vinyl windows have the glass bonded into the sash with no removable stops; for those, a replacement sash from the maker, when it still exists, is often simpler than reglazing.

What to order in the new glass

A replacement sealed unit can be better than the one it replaces. For a heating climate the useful choices:

A low-e coating on the right surface, which keeps more heat in.
Argon fill, a cheap upgrade over air.
A warm-edge spacer, which keeps the edge of the inner pane warmer and cuts the condensation that shows up along the bottom of the glass.
The same overall thickness as the old unit, so it fits the existing stops.

A new sealed unit in an old frame will not perform like a whole new window, because the frame's own air leakage and heat loss stay as they were. For a single fogged unit in a good window, that is fine. Maine's energy code ties its U-0.30 figure to replacement windows; when it is only the glass, the code office is the place to ask if anything more applies.

When the new glass has to be safety glass

The residential code names locations where glass has to be tempered or laminated because people can fall or walk into it. Glass replaced in one of those spots goes back as safety glass, even if the broken pane was plain annealed glass from decades ago. The usual locations:

Any glass in a door, and glass within 24 inches of a door's edge with its bottom under 60 inches.
Big panes near the floor: more than 9 square feet of glass whose lower edge sits below 18 inches and upper edge above 36, beside a place people walk.
Glass near a tub or shower whose bottom edge is under 60 inches above the standing surface.
Glass beside stairs and landings near the walking surface.

Tempered glass is marked with a small etched label in the corner. If the old pane has none and sits in one of these spots, the replacement will be tempered, which takes a little longer to make.

Reglazing old wood sash

A good share of the houses here still have original wood sash, often single-glazed, behind an aluminum or wood storm. When the putty has dried, cracked and fallen out, the glass rattles and water gets into the wood. Reglazing fixes that: the old putty comes out, the bare wood is primed, the glass is bedded and pinned with glazing points, new putty is tooled, and the sash is painted once the putty skins over.

On a house built before 1978, that putty and paint very likely contain lead, so the work is done with lead-safe practices: containment, no dry sanding or open-flame removal, and careful cleanup. A cracked pane of old wavy glass can sometimes be replaced with restoration glass; in a local historic district that can be what keeps the review simple.

Paired with a low-e storm window, a reglazed sash performs far better than its age suggests.

Gothic-style house with carved bargeboard trim, a pointed window and diamond-pane sashes

When new glass is the wrong buy

Replacing a sealed unit makes sense for one or a few windows in a sound frame. It stops making sense when:

Many units in the same house have failed at once, which suggests the others are close behind and a whole-house replacement may cost little more.
The sash or frame is rotten, warped or leaking air around its edges.
The window maker is gone and the sash needs parts nobody stocks.
A bedroom window is too small to serve as an escape opening anyway, so the window has to change size.

We will tell you which side of the line a window is on. On many houses the answer is mixed: new glass in the good windows, new units where the frames have failed.

Cracks in the cold

Winter adds its own glass calls. A pane can crack from a stray piece of ice thrown by a snowblower or slid off a roof, from a ladder leaned against a sash during snow raking, or from heat stress when one part of a large pane is sunlit and another sits in the shadow of a frame or a blind pressed against the glass. A cracked sealed unit has also lost its seal, so it fogs soon after.

Until the new unit arrives, clear packing tape over a crack or a piece of plywood over a broken pane keeps the cold out. In a bedroom, make sure the temporary fix does not block the window as an escape opening. If the damage came from a storm, photograph it before anything is cleaned up; the claim is yours to file, and the photos and a written description of the work help with it.

Common questions about window glass replacement in Portland

Why is there fog between my window panes?

The seal around the sealed unit has failed, so the gas fill escaped and moist air got in. It cannot be cleaned away. A new sealed unit in the same sash fixes it if the frame is sound.

Is replacing the glass cheaper than a new window?

Usually, for one or a few windows in good frames. If many units have failed or the frames are rotten, a new window is often the better use of the money.

Does replacement glass have to be tempered?

Only in the locations the code names, such as in and beside doors, near tubs and showers, large low panes and beside stairs. There, the new glass must be safety glass even if the old pane was not.

Can you replace the glass in old wood windows?

Yes. Single-pane wood sash can be reglazed with new glass and putty; on a pre-1978 house the old putty and paint are handled with lead-safe practices.

How long does new glass take?

Sealed units are made to size, so there is usually a wait of days to a few weeks after measuring. Installing one takes well under an hour per window in most cases.

Where we work

Window glass replacement across greater Portland and southern Maine: Cumberland, York and Sagadahoc counties, from the islands of Casco Bay to the Sebago Lake towns and the New Hampshire line. Each city has its own page with the permit rule and code edition that apply there: