What is a good rule of thumb to decide if I should repair or replace my windows?

I do not want to pay 15k unless I need to. But I also don't want to sink time and energy into repairs if the smart long-term move is to just replace them all. I intend to be in the house for awhile.

Everything I read online is from people selling windows (you should replace them every 20 years), people with very old homes (replacing windows is an aesthetic choice and makes no $ sense) or otherwise does not seem to apply to me.

Yet this has to be a common issue so I suspect I am missing something....


My house was built in 94, and the windows are original to the house. So I think the windows are past their intended lifespan.

One large picture window, and one small bathroom window have moisture in-between the panes in the morning. This seems to indicate a broken seal? It is unclear to me if this can even be fixed without replacing the window.

Many other windows are foggy, which is annoying but fine?

Many windows are difficult to open/close, which I suspect I can repair.

None of them seem to insulate very well anymore.

I got an estimate from home depot to replace them all (19 windows) that comes out at 15-17k.

I can afford this, but it is not an easy expense and would prefer not to. The asthetics of having new windows would be a bonus, but is not a primary consideration.

Things I know I could be wrong about:

  • I suspect that the insulation savings from new windows is not particularly cost-effective. Or even the best use of money if my goal is eco-savings.
  • I suspect the windows with a broken moisture seal will need to be replaced, and that more are likely to have that problem soon. I suspect that I should not let this go unfixed.
  • I suspect the estimate above for new windows is close to avg.

So... That all leaves me with... Should I just spend the money now to save on trouble later because everything will need to be replaced anyways? Or is replacing windows for non-astheic reasons a fools errand and I should tackle this by repairing these problems one by one?

  • 1
    Unless the windows are broken or single pane, replacing is usually not cost effective(even with broken seals). Insulation around the windows will probably need upgrading, and maybe replace caulking.
    – crip659
    Nov 12, 2023 at 18:54
  • "None of them seem to insulate very well anymore." Where do you feel the air leak?
    – FreeMan
    Nov 12, 2023 at 23:23
  • Also, get more than one estimate. We got 3 that were wildly different, but were also for different products.
    – FreeMan
    Nov 12, 2023 at 23:36

1 Answer 1


Moisture, whether droplets or "fog" inside the windows does indicate a failed seal, and the only repair for that is a new sealed pane unit. Depending on the state of the frame that can be only the sealed pane unit (same as you'd do for a broken pane) or the whole window.

It is normally less cost to just replace the sealed pane unit than the whole window, and that will (depending on the replacement unit) get you the bulk of any energy improvement you might get (there are, depending what the old frames do, possible improvements in thermal breaks on the frame itself - or those may already be in place in your old frames) - if you don't notice the frames themselves being particularly cold, or having a lot of condensate on them, they probably do incorporate a thermal break.

If there are major mechanical issues with the old frame, or the flashing is leaking (which often leads to problems with the frame) then replacing the whole window might make more sense than just replacing the sealed glass unit.

If you are trying to evaluate "how to save money on energy" and where replacing windows or panes would fit in that, many places have free or low cost energy audit programs sponsored by the state or a utility company, and in most cases it's true that replacing the windows (unless visually offensive or disfunctional - i.e. not for energy reasons as such) is far down the list, with boring old "add more insulation and seal air leaks" being right at the top, unless you've already done that.

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