1990s upvc windows - worth replacing whole window or just the glass?

ChasingtheWelshdream

We have a problem window, it is a double casement style in a cold north facing room. We think it was installed in the 90s.

One side was misting up so we had the glazing replaced on just that side last year. Since then, that side is covered with condensation most mornings, and during a very cold snap even had ice at the bottom (this bedroom is generally unheated).

In contrast, the adjacent original glass has condensation on the bottom but not the entire surface like the new section.

We had another unit replaced in a different bedroom and again this new glass attracts more condensation than the original. 

The installer returned and says they are fitted correctly and I am reluctant to call him back again, but I need to do something to fix it. The glass must  somehow have a colder surface temperature than the original.

So I have a couple of questions. 

1. Could the new sealed unit have an inferior spec to the originals - eg not argon-filled? We just asked for replacement glass. 

2. Is it worth now replacing with a completely new window given its age, or just try replacing the glazing again? Are new windows that much more heat retentive than those 30 yeas old? The window company will of course say yes.

There are no trickle vents so a replacement would have these.

Just to add the condensation/heating is something we are managing but I am confused that one casement is so much worse than the other.

plumb1_2

They could be fitted incorrectly as the correct side of the glass has to be outside, usually labelled with a sticker before fitting.

FreeBear

Is the condensation on the inside or outside ?

Some mornings, I get condensation on the outside of my new windows - This is good, as it shows that the sealed units are working well.

Nearlyold

Just to confirm do you mean condensation on the indoor or outdoor surfaces. 

ChasingtheWelshdream

Condensation is inside, I use a window vac each morning on it. The replacement unit is usually completely covered, the original side has a couple of inches on the bottom, so a noticeable difference.

Some new windows downstairs get condensation on the outside, but they are South facing, have trickle vents and are in a living room so doesn’t have a human breathing for 8 hours overnight.  I am unsure if they are better units, or if their situation makes it difficult to compare. The originals there didn’t really get condensation as I recall.

I have just checked for any stickers or markings. The only thing I can see are codes stamped on the inside of the (spacer?) bar that separates the inner and outer sheet of glass. The letters face the same way on both the new and original unit, so unsure if that indicates anything. 

ThisIsWeird

Hi CtWD. I don't know.

I need to ask, tho' - where does this condensation come from? How does it get in to that room? What is that room used for?

If it's unheated, then two tgings should be put in place - one is to not allow warm, moist air from the rest of the house to get in there - so not doors left open - and the other is that it should be ventilated thoroughly, as much as its required to remove any moist air before it condenses.

As to why one pane is seemingly performing worse than its neighbours, I just can't see two DG units, of similar thicknesses, behaviour significantly different like this. I think you could argon-fill and Pilk-K your glass until the cows come home, but the only perceivable difference will be in the lab-produced stats that were used to sell them. In practice, an outside temp difference of 1oC would likely, in my mind, override any benefit. But that's just a suspicion, a somewhat cynical one, I know. I just cannot think of any 'fault' in a unit that would do this, or any great loss if the unit wasn't the very best currently available.

So I suspect it'll be down to other issues, like the 'better' unit being closer to an East-facing house corner, or an internal house wall (warmer), or having a better air flow over it (more dry) - something like that.

But I obviously do not know.

ChasingtheWelshdream

It’s a long and frustrating story, but basically down to an incredibly stubborn teenager refusing to have heating on or opening windows. Best not go there on this thread, I am well aware of what should happen 😆

But this, and the other room have that very noticeable difference in the two adjacent panes, within the same window. Ice on the inside of one when the other was fine. 

Next time I will take a picture. I was thinking about asking window company to quote for a complete replacement, but if replacing a frame has no benefit then it would be a waste of money.

BUFF

ThisIsWeird said:

As to why one pane is seemingly performing worse than its neighbours, I just can't see two DG units, of similar thicknesses, behaviour significantly different like this. I think you could argon-fill and Pilk-K your glass until the cows come home, but the only perceivable difference will be in the lab-produced stats that were used to sell them. In practice, an outside temp difference of 1oC would likely, in my mind, override any benefit. But that's just a suspicion, a somewhat cynical one, I know. I just cannot think of any 'fault' in a unit that would do this, or any great loss if the unit wasn't the very best currently available.

So I suspect it'll be down to other issues, like the 'better' unit being closer to an East-facing house corner, or an internal house wall (warmer), or having a better air flow over it (more dry) - something like that.

But I obviously do not know.

A 90s typical DGU woud likely have an U-value of ~ 2.5,  a modern argon-filled/low E glass/warm edge spacer glass one ~1.4 (albeit that would probably also have a different depth of sealed unit).
Realistically you need to know the exact spec. of the original & what replaced it to compare.

No doubt the system manufacturers would also say that current frames are also better thermally than those from the 90s. Iirc they used to say that the lifespan of UPVC frames was ~30 years - not sure if that is still current.

Eldi_Dos

Is the window with the more noticable condensation open for any period of time letting the inner pane get colder.

When the new unit was installed did anything happen to the frame that could now lead to draughts which may make condensation more likely on that side.

ChasingtheWelshdream

No, there is another window on the opposite side of the room that is always cracked open, but this one isn’t. (Until I sneak in once teenager is out to window vac and then I open both for a few minutes to air it).

Nothing untoward happened that we know of. The window fitter had to get a replacement sent through as the first one was the wrong size apparently but no dramas. 

The other replacement unit in a different room also has a noticeable difference but not as bad, as this is on a different aspect.

All we know a about the windows is they were fitted by Everest (stamped on them) and anecdotally were fitted in the 90s.