How to Know if Insulated Windows Need Replacing

I have 30-year-old insulated windows. A salesman told me that the seals are broken, and I am losing heat. To me the seals look fine and I speculate that broken seals should lead to condensation in the double panes. What is the best way to determine if the seals are leaking and windows need replacement?

Hi Deepak,
While condensation or discoloration inside the glass usually occurs when the seals are broken, there are other factors to consider that can affect the insulation performance of your windows even if the seals are intact, such as:

  • The insulating qualities of the argon gas used between layers of glass diminishes over time as it slowly leaks out at a rate of about 1% per year, which can cause a reduction in the insulating value of windows.
  • Newer windows can be ordered with Low-E coatings designed for your climate that can reduce energy loss by as much as 30%-50%.
  • The weather stripping around your windows may have become worn, allowing air leakage.
  • Newer vinyl clad wood frames insulate better than older metal frames.

The bottom line is that replacing your windows (or the glass in them), may increase the insulation value, but you will have to weigh the savings against the cost incurred.


Further Information


  1. Dear Danny,

    I recently bought a house with double-pane vinyl windows with fake muntins (or grills) between the panes. I really hate the cheap and inauthentic look of the fake muntins. I have been trying to research whether it is possible to remove these fake muntins– perhaps by having a glazier unseal the IGU and take out the muntins. But is this even possible? And if it is possible, is it wise? Can the windows be effectively sealed again?

    Many thanks for your advice,

    • Hi Katie,
      As far as I’m aware, it’s not possible to unseal dual pane glass to remove the mullions, nor would you want to if you could, since the space between the glass contains a special gas (usually argon) that increases the insulating properties of the window. In addition you would be sealing humid outside air into the space when you resealed them, which could cause condensation to form between the glass.

  2. Dear Danny,
    We live in a modular home and find that the front door is gaping at the opening side on the top; along with the storm door. The siding continues to look level and we really don’t know what we can do to remedy this problem. We’re on fixed income, live in a modular home park and wondered if you had any ideas.

    • Hi Dave,
      Sounds like the wall has settled on the hinge side, or the door unit frame wasn’t installed square and level in the first place. In either case, it’s not an easy fix and will require removing the frame and rehanging the door. Other fixes that aren’t as good include cutting the top of the door at a slant and rehinging it, or cutting a wedge shaped piece of wood the thickness of the door and attaching it to the top with adhesive and nails or screws. Good luck with your project!

  3. Dave,
    We built a house 5 years ago and have double pained windows. My problem is that the windows have been having condensation on the inside. It isn’t between the glass it is on the inside. I can wipe it off but I really don’t want to have to to this to about every window in the house everyday. Is there something that I can do to correct the problem?

  4. I had this same problem with the moisture forming and it got old washing the windows every day so I stopped and mold formed. I called our neighborhood handyman and he told me that the house was sealed up to tight and that we needed to vent more, open windows, run a fan periodically and open our drapes.
    I got into the routine of opening the front and back door every moorning and left them open while i opened all the drapes and blinds, then i closed the doors. I made sure everyone used the vents int he bathroom when showering and used a vent when I cooked and that fixed the problem. We did use dry-z-air for about the first week in the living room which had the most moisture on the windows.

  5. We had a triple pane window installed in our living room about 6 years ago. About 3 years ago, we noticed “dirt” marks between the panes. It looks like someone cleaned the windows, but left streak marks and it is between the panes of glass. Looks terrible and is getting worse. I assume that the seal must be broken and if so, do I need to replace the whole window or what can be done to fix it?

  6. My double glazed window is perfectly fine except the mutin that is placed half way across has fallen to the bottom.How can I put this back please.

  7. Hi,
    I just got all my windows replaced from aluminum to vinyl and to my surprise now the rooms that were the warmest are really cold. The whole house is cold now. I want to know if the windows that they claimed to be really good and have argon gas to insulate is just a fake statement. What can i do to find out if the windows have argon gas and if they are property installed? They were shorter than the older windows, but when i complained about it they claimed they needed to have gaps to put insulated foam between the windows. It doesn´t feel right. the company is also the manufacturer and family owned and they cover each other. Please help!
    I am located in SLC, UTAH.

  8. I recently purchased a 40 year-old metal moble home. Is it feasible to replace the old exiting windows with double pane windows?

  9. The 2003 ThermaStar Pella vinyl Sliding windows have flakes of rust-like debris at the bottom along a silver metal edge between the vinyl base, as well as a very small amount of of water droplets. There are seven 48×48 windows in this room which faces east. I love the light and don’t know if replacing windows with another type is necessary. I am retired and will continue living in this, our first, home (built in 1969). I would appreciate your advice on the available options i.e., replace, repair or buy a different style. I heard vinyl covered wood doesn’t have problems with condensation???
    Thank you,
    Seventy and learning
    P.S. Spanish Fort, AL is our location

  10. We have Pella Windows and the warranty has not expired yet. Two of the windows have condensation on them every morning and it takes a few hours to clear up. We’re not sure why this is happening to only two of the windows as we have 7 large picture windows in our living/dining combination. It appears that the condensation is on the outside, does this mean the seal is broken? What does this mean?

    • Hi, Thomas, features home improvement advice from the nationally syndicated TV show “Today’s Homeowner” and its experts.
      We don’t offer information on individual home builders, repairers and suppliers, but we encourage checking your local phone listings for this information.
      Thanks for your question, and good luck!

  11. Thanks for letting me know that Low-E coatings can be used with windows to increase energy efficiency. My husband and I want to replace our windows. Maybe we could get some with coatings that will make them better.


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