Here is another.... thank you!

Here is another.... thank you!

{{!gwi}}

Tara
You need new windows, they are shot ( no way around it). . Your current windows are low quality( builders grade) windows that are warped and were never really meant to last or exhibit any form of energy efficiency.
Vinyl windows are a great option as long as they are high quality, which is why they have better performance numbers than a wood window in both structural and energy efficiency. An added bonus is that they actually look nice and add value to your home.
Some higher quality vinyl windows to look at ( depending where you live ) are the following:
Okna ,HiMark, Soft Lite, Sunrise, or Gorell.
Beware of contractors who claim they can put a " band aid " on your current windows. I've seen your windows a thousand times, air leakage is a big issue that cannot be remedied other than new windows.

tara, have you tried pushing the upper sash all the way up? I know that sounds like a ridiculously silly solution, but most calls that we get for this issue have upper sashes that have simply drifted down. If the upper is all the way up and the lower is all the way down and you are still off by 1/2", then mmarsel's recommendation is probably correct. You either have a major installation issue or product failure. Do you see any bowing in the sill or head jamb that would interfere with the travel of either sash?

Toronto Tim,

Pretty simply.

If the customer has pushed the window up or if it is a single hung, the failure of that window (original and new construction/builders grade junk) is complete.

The sills bow from being set improperly, being a poor product, or a combination of the two and there is nothing to fix.

It is a pretty common occurrence and we see it all the time.

I don't think that mmarse is really going out on a limb here and I know that he has seen it as much as I have.

Sorry to be the bearer of bad news Tara.

Is the upper sash all the way up?

What you are probably a victim of is called Brick-bind. The windows are too tight in the opening which can cause the sill to bow upwards and not allow full travel of the lower sash.
It's a generic term and is used on houses even thought they may not be brick.
Sight down the sills from the side and see if they are bowed or crowned up.

"Sight down the sills from the side and see if they are bowed or crowned up. "

Use a level or long straightedge.

Looks like the sash is the "marine glazed" type as best as I can tell. The bowing of the sash width is (was) a problem. If the sash is bowed, tap the sash up with a mallet or the handle of a hammer and see if it moves. Also, check and see if the interlocks are hitting, forcing the top sash down when you
close the window. But...make sure the top sash is up all the way, that's the first step.

There might be hope for these windows. From the location of the lock to the keeper(1st pic) it appears that the two sashes might be misaligned. This could be due to improper installation. It also could be product issues. My recommendation-shop around and find a quality, reputable window installer that would be able to check out the installation first. Might cost a little-but a lot less than replacing them.

I stopped posting on this discussion waiting for the original poster to chime in with any sort of feedback on what they've figured out given all the input they've gotten.

So far nothing in 11 days. Anyone keen to post here might want to wait for 'tara2009' to drop back in on this and provide a bit more info.

To the professional window installers: I'm a home inspector and see this problem frequently. Is it possible in such a case to have one of the sashes shortened so that the locks engage? If a sash can be diassembled to replace a failed or broken IGU, then what about changing the height of said sash?

When this problem surfaces on a new installation, it is possible (albeit unlikely) that one of the sashes was manufactured slightly too tall.
In a situation where there are existing windows that have been installed for awhile, the problem typically arises from a poor quality window that bows, or a poor installation that worsened the condition over time. Modern vinyl windows have fully welded sash stiles and rails, so it is not possible to disassemble. They have snap-in glazing beads that pop in and out for glass replacement. Even the older mechanically fastened units use that same method, and it would be very tedious and not at all advisable to try and cut down the height of a sash.
Generally speaking if you are seeing a situation similar to the OP in your inspections with a 15 yr old home/window, it has just about reached its life expectancy. A high quality product regardless of material can/should last far longer, however it is VERY rare to find anything better than "builder-grade" quality windows in a situation such as that.
That would be my reinforcement to the OP in this post as well: if it is not something as simple as the upper sash having drifted down (assuming of course that they are double, not single hung), you are getting to the point where you should start planning for replacement with a quality product. I don't want to sound like a sleazy window salesman in saying that, but unfortunately that is likely the case if you want to see any level of improved performance from your windows.

+1 again to HomeSealed perfect advice.

You are on borrowed time in these cases and attempts to lock the window are usually only prolonging the inevitable.

I have helped out clients in the past by moving the lock mechanism up to compensate for the lack of proper aliment but the problem worsened over time.

As far as shortening the sash...while possible, it would be dangerous and cost prohibitive in most cases.