Window seal repair: what to know

What the job involves, what changes the price, and what to ask a pro.

What window seal repair is

Window seal repair fixes failed seals on insulated glass or worn weather seals on window sashes to stop fogging, drafts and leaks. Depending on the window, the fix may be a new glass unit, a reglazed sash or new weatherstripping. People call when moisture or fog appears between the panes or when air leaks around a closed sash.

Signs you need it

  • Fog, condensation or a film of moisture between the two panes of insulated glass that will not clear
  • A milky haze or mineral film between the panes that wiping the glass does not reach
  • Drafts you can feel around a closed sash, or a whistle when the wind blows
  • Weatherstripping that is flattened, cracked, torn or missing along the sash
  • A sash that does not close tight or leaves a gap at the meeting rail

What the pro does

  • Check the window for fogging, failed seals, frame condition and how the sash closes, then mark what needs to be fixed
  • Remove the sash or glass unit carefully, checking the glazing bead, the glazing points and the frame channel for damage
  • Replace the insulated glass unit with a new one sized to the opening, or reglaze the sash with new glazing compound where that suits the window
  • Install new weatherstripping in the sash channel and the meeting rail, sized so the sash closes evenly
  • Test the sash for smooth operation and tight closing, and check the new glass for clarity and seal

What changes the price

Every job is different, so we do not publish prices. These are the things that move the quote up or down.

  • Number of windows with failed seals and whether the glass unit or the sash must be replaced
  • Glass unit type, such as low-E, gas-filled or laminated glass, and its size
  • Frame condition, since a warped frame or rotted sash adds time and parts
  • Weatherstripping type and the number of sashes that need it
  • Access, including second-story windows and any exterior work
  • Whether the window is a standard size or needs custom glass
  • Whether the job is a glass unit swap or a full window replacement

What a written quote should spell out

  • Each window listed by location, with the fault found and the repair chosen
  • Glass unit size, type and coatings, with the gas fill and spacer listed
  • Weatherstripping type, length and where it is installed
  • Glazing compound or glazing points used if a sash is reglazed
  • Frame and sash repairs shown as separate lines, with photos of any damage
  • Cleanup and removal of old glass and debris, with any broken glass handled safely

Questions to ask before you hire

  • Is the fog between the panes a failed seal, and can you show me the seal on the glass?
  • Will you replace the glass unit, or reglaze the sash, and which is better for my window?
  • What coatings and gas fill are in the new glass unit, and will they match the old glass?
  • Will the new weatherstripping stop the draft, and how will you test it?
  • What warranty covers the glass seal, and what could void it?
  • How do you handle the old glass without breaking it in the frame?
  • If the frame is damaged, what will that add to the price?

Red flags

  • Defogging or a seal kit sprayed in between the panes as the fix for a failed glass unit
  • Glass replaced with a different size or without matching the coatings the window needs
  • Weatherstripping stapled in without fitting the channel
  • A quote that does not say whether the glass unit or the sash is being replaced
  • Pressure to replace all windows when one or two have failed seals

What you can do yourself

You can safely clean the glass and replace worn weatherstripping on a ground-floor sash with a kit sized for the channel. Do not remove insulated glass or a sash from an upper-story window, since broken glass and a falling sash can cause serious injury. Call a pro for failed glass seals, reglazing, and any sash that is warped or hard to close.

Licenses and permits

Window seal and glass repair is commonly done by licensed glass or window companies, and rules vary by place. Check with your state and local licensing agency, and check for a permit if the work changes an exterior or structural element.

Window seal repair questions

Can fogged windows be cleared?

Usually not. Fog between the panes means the seal has failed and moisture is inside the unit. Cleaning or drying cannot fix it. The unit must be replaced.

Will a new glass unit fit my old frame?

Often, if the size is measured correctly and the frame is sound. The installer should check the glazing channel and the spacer, and say so if the frame needs repair first.

Is reglazing the same as replacing the glass?

No. Reglazing removes the old glazing compound and sets the glass again in the sash. It suits some sashes with failed glazing, but a failed insulated unit needs a new glass unit.

Why does the draft come back after weatherstripping?

Usually the strip is the wrong size, is compressed too far, or the sash is out of square. A pro should check the sash and the fit before adding more strip.

About this guide

This national guide is written and checked by infinibell. Rules and conditions differ by place, so local pros are credited on guides for the cities they serve, not on national ones.

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